NEW INVADERS OF THE NORTHEAST

AND NORTHCENTRAL 

UNITED STATES

Karan A. Rawlins, Rachel L. Winston, Charles T. Bargeron, 

David J. Moorhead, and Rachel Carroll

FHTET-2017-04

January 2018

US Department 

of Agriculture

TECHNOLOGY

TRANSFER

Forest Health Assessment 

and Applied Sciences Team
a b d

c

e

f g h

Cover photos: a. Vitex rotundifolia infestation; b. V. rotundifolia flower 

(a,b. Forest & Kim Starr, Starr Environmental); c. Clematis vitalba

flower; d. C. vitalba infestation (c,d. Robert Vidéki, Doronicum Kft., 

bugwood.org); e. Broussonetia papyrifera (Chuck Bargeron, University 

of Georgia, bugwood.org); f. B. papyrifera inflorescence (Daderot); 

g. Narcissus pseudonarcissus flower (BerndH); h. N. pseudonarcissus 

infestation (Sapin 88)

The Forest Health Technology Enterprise Team (FHTET) was created in 1995 by the Deputy Chief for State 

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the health of American forests. FHTET became Forest Health Assessment and Applied Sciences Team 

(FHAAST) in 2016. This booklet was published by FHAAST as part of the technology transfer series.

http://www.fs.fed.us/foresthealth/technology/

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How to cite this publication: Rawlins, K.A., R.L. Winston, C.T. Bargeron, D.J. Moorhead, 

and R. Carroll. 2018. New Invaders of the Northeast and Northcentral United States. USDA 

Forest Service, Forest Health Assessment and Applied Sciences Team, Morgantown, West 

Virginia. FHTET-2017-04. 
NEW INVADERS OF THE NORTHEAST 

AND NORTHCENTRAL UNITED STATES

Karan A. Rawlins

Center for Invasive Species and Ecosystem Health, University of Georgia, Tifton, GA

krawlins@uga.edu

Rachel L. Winston

MIA Consulting, LLC, Sandpoint, ID, rachel@getmia.net

Charles T. Bargeron

Center for Invasive Species and Ecosystem Health University of Georgia, Tifton, GA

cbargero@uga.edu

David J. Moorhead

Center for Invasive Species and Ecosystem Health, University of Georgia, Tifton, GA

moorhead@uga.edu

Rachel Carroll

Center for Invasive Species and Ecosystem Health, University of Georgia, Tifton, GA

Rachel.Beyke@uga.edu

This publication is available online at: 

https://www.fs.fed.us/foresthealth/technology/pdfs/FHTET-2017-04_New_

Invaders_Northeast.pdf

Acknowledgments

The authors wish to thank Christopher Evans (UIUC NRES) for his review and helpful 

comments on this publication. Some of the material in this guide was revised from the sister 

guides “New Invaders of the Northwest and Southwest”. We acknowledge and express our 

appreciation for the additional authors of those guides: Rachel Winston, Carol Bell Randall, 

Wendy DesCamp, Jennifer Andreas, Joseph Milan, and Mark Schwarzländer. We would like 

to thank all of the photographers who granted permission for the use of photos. The vast 

majority were obtained via a Creative Common license and are included herein under the 

same license; no changes were made to those images. The layout of this guide was designed 

by Rachel Winston. We also extend our gratitude to Richard Reardon (Forest Service-Forest 

Health Assessment and Applied Sciences Team) for producing this guide.
New Invaders of the Northeast and Northcentral United States

TABLE OF CONTENTS About This Field Guide...........................................2

If You Find a New Invader.............................................3

Invasive Plant Regulations..................................4

New Invaders .................................................................8

Bluish-Purple Flowers .........................................8

Common bugloss, Anchusa officinalis.................................................8

Beach vitex, Vitex rotundifolia..........................................................10

Butterfly bush, Buddleja davidii.......................................................12

Green Flowers ........................................................ 14

Amur silvergrass, Miscanthus sacchariflorus.......................................14

Feathertop, Calamagrostis epigejos ....................................................16

Golden bamboo, Phyllostachys aurea ................................................18

Yellow groove bamboo, Phyllostachys aureosulcata.............................18

Ravenna grass, Saccharum ravennae .................................................20

Wavyleaf basketgrass, Oplismenus undulatifolius...............................22

Japanese chaff flower, Achyranthes japonica.......................................24

Spiny emex, Rumex spinosus.............................................................26

Fragrant clematis, Clematis flammula...............................................28

Traveler's joy, Clematis vitalba .........................................................28

Amur corktree, Phellodendron amurense...........................................30

Japanese zelkova, Zelkova serrata......................................................32

Paper mulberry, Broussonetia papyrifera............................................34

Pinkish-Purple Flowers.................................... 36

Himalayan balsam, Impatiens glandulifera........................................36

Milk thistle, Silybum marianum.......................................................38

Ragged robin, Silene flos-cuculi ........................................................40

Chocolate vine, Akebia quinata .......................................................42

Japanese spiraea, Spiraea japonica.....................................................44

Shrub lespedeza, Lespedeza bicolor....................................................46

Chinaberry tree, Melia azedarach.....................................................48

Japanese maple, Acer palmatum .......................................................50
New Invaders of the Northeast and Northcentral United States

White Flowers........................................................52

Baby's breath, Gypsophila paniculata...............................................52

Broadleaved pepperweed, Lepidium latifolium ................................54

Burnet-saxifrage, Pimpinella saxifraga .............................................56

Goatsrue, Galega officinalis .............................................................58

Italian arum, Arum italicum............................................................60

Queen of the meadow, Filipendula ulmaria ....................................62

Tara vine, Actinidia arguta..............................................................64

Deutzia, Deutzia scabra ..................................................................66

Japanese pachysandra, Pachysandra terminalis .................................68

California privet, Ligustrum ovalifolium.............................................70

Chinese privet, Ligustrum sinense.......................................................70

Glossy privet, Ligustrum lucidum .......................................................70

Japanese privet, Ligustrum japonicum.................................................70

Doublefile viburnum, Viburnum plicatum var. tomentosum..............76

Linden viburnum, Viburnum dilatatum ............................................76

Siebold's arrowwood, Viburnum sieboldii..........................................76

Castor aralia, Kalopanax septemlobus ...............................................80

Kousa dogwood, Cornus kousa........................................................82

Yellow Flowers......................................................84

Common daffodil, Narcissus pseudonarcissus....................................84

Dalmatian toadflax, Linaria dalmatica............................................86

Fig buttercup, Ficaria verna............................................................88

Oldwoman, Artemisia stelleriana.....................................................90

Tansy ragwort, Jacobaea vulgaris .....................................................92

Yellow hornpoppy, Glaucium flavum ..............................................94

Wintergreen barberry, Berberis julianae...........................................96

Aquatic Species.......................................................98

Bog bulrush, Schoenoplectiella mucronata ........................................98

Variable flatsedge, Cyperus difformis ..............................................100

European frog-bit, Hydrocharis morsus-ranae.................................102

European speedwell, Veronica beccabunga .....................................104
New Invaders of the Northeast and Northcentral United States

TABLE OF CONTENTS

European waterstarwort, Callitriche stagnalis ................................106

Giant salvinia, Salvinia molesta .....................................................108

Mudmat, Glossostigma cleistanthum...............................................110

Onerow yellowcress, Nasturtium microphyllum .............................112

Yellow floatingheart, Nymphoides peltata.......................................114

Glossary...................................................................... 116

Selected References ............................................ 120

References for Plant Identification and Terminology...124

References for More Established Invasive Plants..........124
New Invaders of the Northeast and Northcentral United States
2 New Invaders of the Northeast and Northcentral United States INTRODUCTIONAbout This Field Guide

The purpose of this guide is to help landowners and land managers recognize new 

invasive plants that are not yet widely distributed, so they can be treated rapidly and 

eradicated rather than becoming large and expensive problems. Invasive plants are a 

major concern worldwide. They displace native species, decrease forage and agricultural 

production, alter nutrient and water cycling, and lower the aesthetic value of natural 

areas. With the increase of world travel, exotic plant introductions are on the rise. 

Not all newly introduced species become invasive. Those which do often follow an 

invasion pattern; they remain at low levels for several years or decades (lag phase) 

and then enter a phase where they increase dramatically. Attempting to control 

large invasive plant infestations is a costly endeavor; it is much more cost effective 

to allocate resources toward invasive plant prevention or the rapid treatment of 

new introductions. Unfortunately, the process of adding newly introduced species 

to watch lists or control lists is frequently tedious and lengthy. By the time many 

invasive species are on the radar, they have become widely established. 

This guide focuses on species considered problematic in the 20 states that comprise 

the northeastern and northcentral United States: Connecticut, Delaware, Illinois, 

Indiana, Iowa, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, 

New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, 

Vermont, West Virginia, and Wisconsin. Not all species included herein will be 

problematic in all portions of this region. 

The species in this guide were selected through a multi-step process by:

1. First combining the noxious weed, watch, and new invader lists/alerts of 

northeastern/northcentral states and regional exotic plant councils

2. Adding species with high ecological impact ratings as assigned by the 

NatureServe and state and regional exotic plant councils

3. Identifying which of the above species are not yet widespread throughout the 

northeastern/northcentral United States

4. Eliciting the opinions of numerous state and regional invasive plant experts to 

narrow the candidate list to those present in this guide

It was not possible to include all new species of concern, but this manual will 

hopefully serve as a good starting point. The plants included herein are arranged 

first by flower color, and then grouped with related species progressing from grasses 

through forbs, vines, shrubs, and trees. Aquatic plants are given their own section. 

Non-flowering terrestrial plants are included in the green flower section; nonflowering aquatic plants are included in the aquatic section. Select definitions of 

plant terms are included in the glossary. For more in-depth explanations of plant 
New Invaders of the Northeast and Northcentral United States 3

parts and plant life cycles, or for more help with plant identification, please see 

the suggested references listed at the end of this guide. Additional references are 

also provided for guidebooks and websites with identification information on 

other, more established invasive plants in the region.

Each plant is represented by multiple photos and descriptions emphasizing key 

identification traits and ways to distinguish it from look-alike species. Attempts 

were made to utilize the most current scientific names for all invasive plants. The 

GRIN (Germplasm Resources Information Network), GBIF (Global Biodiversity 

Information Facility), databases and ITIS (Integrated Taxonomic Information 

System) were largely followed in this regard, with input from taxonomists and 

other sources. Please note the scientific names for many species have changed since 

previous invasive plant publications. 

Plant distribution data is presented in a map for 

each species. This information was sourced from the 

Early Detection & Distribution Mapping System 

(EDDMapS, www.eddmaps.org). Distribution 

information was also provided by individuals and 

recent invasive plant alert reports. Counties where the 

invasive plant has been documented are colored red. 

Some documented populations of invasive plants have since been eradicated. The 

locations of these populations are still included in the distribution maps because it 

is possible some plants, seeds, or propagules survived.

Invasive plant spread is often rapid. Even if an invasive plant is not depicted as 

occurring in a specific region, it could have spread into that region since the 

collection of distribution information presented herein. Particular care should be 

taken searching for species in areas surrounding known infestations, as invasive 

plant spread into nearby areas is likely. 

If You Find a New Invader

Should you find one of the species listed in this manual in a new region (or a 

species you believe to be a new invader), notify your local invasive plant authority 

immediately (e.g. your county weed superintendent or state department of 

agriculture), and devise a treatment plan to eradicate the infestation as promptly as 

possible. The infestation should also be mapped and submitted to the EDDMapS 

database. For more information on how to utilize or contribute to the EDDMapS 

tools, visit www.eddmaps.org/about/ and apps.bugwood.org/.
4 New Invaders of the Northeast and Northcentral United States INTRODUCTIONInvasive Plant Regulations

Some species in this guide are listed as noxious, prohibited, or restricted within a 

state(s). Where applicable, this information is included in a special section on the 

species' description page. Regulations pertaining to these designations are given in 

the table below. This table is for informational purposes only and should not be 

interpreted as complete, nor should it be considered legally binding. Coordination 

with your state plant regulatory agency is recommended to stay up-to-date on 

revised regulations for any species included in this guide.

State Designation Definition

Connecticut (CT) Prohibited

Species for which importing, moving, selling, 

buying, cultivating, distributing, or transplanting is 

prohibited, regardless of any municipal ordinance 

to the contrary.

Delaware (DE) Noxious Species that are not allowed to exceed 24 inches in 

height or allowed to produce seed.

Illinois (IL)

Aquatic Injurious 

Plant

Aquatic species that are not allowed to be possessed, 

bought, sold, distributed, offered for sale, or planted 

within the state without an IDNR-issued permit.

Noxious

Any plant which is determined by the Director, 

the Dean of the College of Agriculture of the 

University of Illinois and the Director of the 

Agricultural Experiment Station at the University 

of Illinois, to be injurious to public health, crops, 

livestock, land or other property.

Prohibited Exotic 

Weed

Species that are not allowed to be bought, sold, 

distributed, offered for sale, or planted within the 

state without an IDNR-issued permit.

Indiana (IN)

Noxious

Plants that are under control programs, and/or are 

prohibited or restricted from sale or distribution in 

Indiana.

Prohibited Invasive 

Aquatic

Species for which it is illegal to (1) sell, offer 

for sale, gift, barter, exchange, or distribute, (2) 

transport on or within any: boat, trailer, motor 

vehicle, bait bucket, fishing gear, creel, tackle, tackle 

box, or other means.

Iowa (IA)

Noxious Plants that are under control programs, and/or are 

prohibited or restricted from sale or distribution.

Aquatic Invasive 

Species

Species which it is illegal to possess, introduce, 

purchase, sell, or transport in Iowa.

Maine (ME) Noxious Species that are illegal to import, export, buy sell or 

intentionally propagate in Maine. 
New Invaders of the Northeast and Northcentral United States 5

State Designation Definition

Maryland (MD)

Noxious Plants that are under control programs, and/or are 

prohibited or restricted from sale or distribution.

Invasive (Tier 1)

Plants that may not be propagated, imported, 

transferred, sold, purchased, transported, or 

introduced.

Invasive (Tier 2)

Plants that a person may not sell or offer for sale 

at a retail outlet unless the retail outlet posts in a 

conspicuous manner in proximity to such plant 

displays, a sign identifying the plants as Tier 2 plants.

Massachusetts 

(MA) Prohibited Species that are prohibited from sale, trade, purchase, distribution and related activities.

Michigan (MI)

Noxious (Prohibited) Species whose seeds are prohibited as contaminants 

in seed offered for sale.

Noxious (Restricted) Species for which the contaminant limit is one 

seed per 2000 of agricultural seed offered for sale. 

Prohibited

Species that cannot be sold or grown in the 

state. and whose fragments, seeds or a hybrid 

or genetically engineered variant thereof are 

specifically prohibited.

Restricted

Species for which any plants, fragments, seeds or a 

hybrid or genetically engineered variant thereof are 

restricted.

Minnesota (MN)

Noxious (Control)

Prohibited noxious weeds listed to be controlled 

are plants established throughout Minnesota or 

regions of the state which must be controlled, 

(efforts must be made to prevent the spread, 

maturation and dispersal of any propagating 

parts, thereby reducing established populations 

and preventing reproduction and spread), and their 

transportation, propagation, or sale is prohibited.

Noxious (Eradicate)

Prohibited noxious weeds listed to be eradicated 

are not currently known to be present in 

Minnesota or are not widely established. 

These species must be eradicated, and their 

transportation, propagation, or sale is prohibited.

Prohibited Seed Species whose seeds are prohibited as contaminants 

in seed intended for planting.

Restricted Seed Species for which the contaminant limit is 25 per 

pound of seed intended for planting. 

Specially Regulated 

Plant

Plants that may be native species or have 

demonstrated economic value, but also have 

the potential to cause harm in non-controlled 

environments.
6 New Invaders of the Northeast and Northcentral United States INTRODUCTIONInvasive Plant Regulations (continued)

State Designation Definition

Missouri (MO) Noxious Plants that are under control programs, and/or are 

prohibited or restricted from sale or distribution.

New Hampshire 

(NH)

Prohibited Aquatic

Exotic aquatic weeds for the which the sale, 

distribution, importation, purchase, propagation, 

transportation, or introduction into the state is 

prohibited.

Prohibited Terrestrial

Terrestrial species for the which no person shall 

collect, transport, import, export, move, buy, sell, 

distribute, propagate or transplant any living and 

viable portion of any plant.

New Jersey (NJ) Noxious Seed

Seed which contains in excess of a pre-determined 

limitation (%) of noxious weed seeds is prohibited 

from sale or must have the noxious weed species 

and amounts clearly labelled (limitations based on 

species).

New York (NY)

Prohibited

Plants that are prohibited from sale, purchase, 

possession, propagation, introduction and 

transport in New York State.

Regulated

Plants that cannot be knowingly introduced into 

a free-living state, or introduced by a means that 

one should have known would lead to such an 

introduction, although such species shall be legal 

to possess, sell, buy, propagate and transport.

Ohio (OH) Noxious Plants that are under control programs, and/or are 

prohibited or restricted from sale or distribution.

Pennsylvania (PA) Noxious Plants that are under control programs, and/or are 

prohibited or restricted from sale or distribution.

Rhode Island (RI)

Noxious Plants that are prohibited from movement into or 

within Rhode Island.

Noxious Seed Species for which the sale of agricultural, vegetable 

or lawn seed containing any seeds is prohibited.

Vermont (VT)

Noxious A

Noxious weeds that are not native to the State, 

not currently known to occur in the State on the 

date of listing, and pose a serious threat to the 

State. They are prohibited or restricted from sale, 

possession, cultivation, or distribution.

Noxious B

Noxious weeds that are not native to the state, 

are of limited distribution statewide, and pose a 

serious threat to the State, or any other designated 

noxious weed being managed to reduce its 

occurrence and impact in the State. They are 

prohibited or restricted from sale, possession, 

cultivation, or distribution.
New Invaders of the Northeast and Northcentral United States 7

State Designation Definition

West Virginia 

(WV) Noxious

Species for which it is illegal to move, transport, 

deliver, ship or offer for shipment into or within 

West Virginia.

Wisconsin (WI)

Noxious Plants that are under control programs, and/or are 

prohibited or restricted from sale or distribution.

Prohibited

Invasive species that are not currently found in 

Wisconsin, with the exception of small pioneer 

stands, but which, if introduced into the state, are 

likely to survive and spread, potentially causing 

significant environmental or economic harm or 

harm to human health. The transport, possession, 

transfer and introduction of these species is not 

allowed.

Restricted

Invasive species that are already established in 

the state and cause or have the potential to cause 

significant environmental or economic harm 

or harm to human health, and for which the 

transport, transfer and introduction are prohibited, 

but possession is allowed.
8 New Invaders of the Northeast and Northcentral United States BLUISH PURPLE FLOWERSCommon bugloss

Anchusa officinalis L.

SYNONYMS: alkanet, bee bread, Anchusa angustifolia L.

ORIGIN: Europe

GROWTH TRAITS: Upright, herbaceous growing 1-3' (30-90 cm) from a deep 

taproot. It is a basal rosette in its first year. Plants that behave as biennials bolt 

several flowering stems their second year before dying by their second winter. 

Plants growing as perennials bolt one flowering stem the second year and several 

stems thereafter. Stems and leaves are fleshy and hairy. Leaves are narrowly lanceshaped and decrease in size further up the stem. Basal leaves are stalked while 

stem leaves are alternate and clasp the stem. Flowers are produced from late 

spring to early fall in fiddleneck clusters at the ends of stems and branches. With 

maturity, fiddlenecks unfurl and straighten. Each flower is bluish-purple with a 

white center and has 5 petals fused at their bases to form a trumpet shape. Each 

flower produces a 4-chambered nutlet, and each nutlet produces one seed.

a b

Common bugloss a. plant; b. small infestation (a. © Gerald D. Carr 2017; b. John M. Randall, The 

Nature Conservancy, bugwood.org)
New Invaders of the Northeast and Northcentral United States 9

Family Boraginaceae

c d e

Common bugloss c. leaves and stem; d. flowers; e. fruit bases with 4 nutlets each (c. Andreas 

Rockstein; d. © Marco Munari, iNaturalist.org; e. © Gerald D. Carr 2017)

REPRODUCTION: Spreads by seed. Seeds may remain viable in the soil for 

many years.

HABITAT: Does best in full sun in moist but welldrained conditions. It can be found in disturbed 

environments such as roadsides, pastures, and 

cultivated fields.

LOOK-ALIKES: Several native and exotic species 

in the Boraginaceae family resemble common 

bugloss with their bluish fiddleneck flowers, 

alternate and hairy leaves, nutlet fruits, and erect 

growth form. The combination of small, deep 

blue, uncurved, tubular flowers with white centers, 

fleshy stems and leaves, and narrow leaves larger 

at their base help differentiate common bugloss. 

The exotic blueweed (Echium vulgare) and Patterson's curse (E. plantagineum) 

are very similar, but their flowers are less tubular, and their upper petal lobes 

overhang the lower lobes. The exotic small bugloss (Anchusa arvensis) differs 

from common bugloss by growing smaller, having smaller blue flowers, and 

having warty foliage.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state. 

NOTES: Common bugloss frequently invades 

pastures and can cause hay bales to mold.

Look-alike: blueweed 

(Pleple2000)
10 New Invaders of the Northeast and Northcentral United States BLUISH PURPLE FLOWERSBeach vitex

Vitex rotundifolia L. f.

SYNONYMS: roundleaf chastetree

ORIGIN: Asia, Australia, the Pacific Islands (including Hawaii)

GROWTH TRAITS: Prostrate, deciduous shrub or sprawling vine growing up 

to 2' (0.6 m) tall from a deep, minimally-branched taproot. The sprawling stems 

root at the nodes and may spread as much as 33-60' (10-20 m) away. Stems are 

green, square, and fleshy when young. Mature stems are brown, woody, and 

brittle, breaking off easily in high tide and colonizing new areas after rooting 

from stem nodes. Leaves are oval, 1-2" (2.5-5 cm) long, opposite, strongly 

aromatic, and have smooth margins. The upper leaf surface is pale green and 

lightly hairy while the lower surface is silvery-gray and has dense, matted hairs. 

Flowers are 0.3" (8 mm) long, 2-lipped with bluish-purple petals fused at their 

base, and occur in small clusters at the ends of branches. The fruit is round, 

0.25" (6 mm) in diameter, green when young, and dark purplish-black when 

mature. At temperate locations, flowers appear spring to summer, fruits mature 

a b

Beach vitex a. plant; b. infestation (a,b. Forest & Kim Starr, Starr Environmental)
New Invaders of the Northeast and Northcentral United States 11

Family Lamiaceae

c d e

Beach vitex c. leaves; d. flowers; e. fruits (c-e. Forest & Kim Starr, Starr Environmental)

in early autumn, and the plant drops its leaves in winter. In warm climates, the 

plant retains its leaves and flowers year-round.

REPRODUCTION: Spreads by seed and vegetatively by rooting at stem nodes. 

Seeds remain viable in the soil for up to four years.

HABITAT: Does best in sandy soils in full sun. 

Highly tolerant of drought and salt.

LOOK-ALIKES: Several dune species resemble 

beach vitex, including the native Brazilian bayhops 

(Ipomoea pes-caprae ssp. brasiliensis) and gulf 

croton (Croton punctatus). The combination of 

opposite leaves with smooth margins, 2-lipped 

bluish-purple flowers, and low sprawling growth 

form help differentiate beach vitex from potential 

look-alikes. Brazilian bayhops has alternate leaves 

funnel-shaped flowers while gulf croton has 

alternate leaves and non-showy, green flowers.

NOXIOUS WEED LISTINGS: NY (Prohibited)

NOTES: This species was intentionally introduced 

into the continental United States in the 1980s as 

a beach stabilization plant, although it is much less 

effective than native dune grasses that have more 

fibrous root systems.

Look-alike: gulf croton 

(Rebekah D. Wallace, 

University of Georgia)
12 New Invaders of the Northeast and Northcentral United States BLUISH PURPLE FLOWERSButterfly bush

Buddleja davidii Franch.

SYNONYMS: orange eye butterflybush, summer lilac, Texas lilac

ORIGIN: China

GROWTH TRAITS: Deciduous shrub typically growing 6-12' (1.8-3.7 m) tall 

and often equally wide from a deep root system. Stems are dense, outwardarching, 4-angled, often hairy when young, and have scraggly, grayish-brown, 

peeling bark at maturity. There are several varieties and cultivars available which 

vary in their leaf size, leaf color, and flower color. Leaves are opposite, lanceshaped, 2-8" (5-20 cm) long, and have very finely toothed margins. They vary 

from dark green to light silver-green and are hairless above with dense hairs on 

the undersides. Leaves are shed in autumn and replaced by new ones that remain 

over winter. Flowers appear in long, dense, spikes at branch tips from summer 

to early fall. The tiny, tubular flowers have 4 petals that vary from white to deep 

purple and often have orange centers. The fruits are inconspicuous, dry brown 

a b

Butterfly bush a. shrub; b. hillside infestation (a. Ptelea; b. Leslie Mehrhoff, University of 

Connecticut, bugwood.org)
New Invaders of the Northeast and Northcentral United States 13

Family Scrophulariaceae

c d e

Butterfly bush c. leaves; d. flowers; e. fruits (c. © naturewatchwidow, iNaturalist.org; d. Ptelea; e. 

Robert Vidéki, Doronicum Kft., bugwood.org)

capsules that split open when ripe to release numerous dust-like seeds. Plants 

typically live up to 20 years.

REPRODUCTION: Spreads by seed, which may 

remain viable for five years. Cut stems and root 

fragments can also sprout roots and grow into new 

plants.

HABITAT: Tolerates a variety of conditions, but 

grows best in full sun to partial shade in moist, welldrained, fertile soils. It capitalizes on disturbance 

and readily invades forest margins, streamsides, 

fields and moist rock faces.

LOOK-ALIKES: The combination of opposite, 

lance-shaped leaves and long, purple, spike inflorescences help differentiate 

butterfly bush from unrelated look-alikes. Within the genus, most species in 

the USA grow in southern or western states. In the East, the exotic fountain 

butterfly bush (B. alternifolia) has long, weeping inflorescences. The exotic 

Lindley's butterfly bush (B. lindleyana) typically only grows to 5' (1.5 m) tall 

and has more ovate leaves and more tubular flowers.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: This species is still popular in the ornamental 

trade where it is planted to attract bees, butterflies, 

and hummingbirds. It frequently escapes cultivation.

Look-alike: Lindley's butterfly 

bush (Pancrat)
14 New Invaders of the Northeast and Northcentral United States GREEN FLOWERS

Amur silvergrass

Miscanthus sacchariflorus (Maxim.) Hack.

SYNONYMS: silver banner grass, Miscanthus sacchariflorus (Maxim.) Franch.

ORIGIN: Asia

GROWTH TRAITS: Perennial clump-forming grass typically growing 5-8.2’ 

(1.5-2.5 m) tall from a rhizomatous root system. Leaves are 1-3’ long (0.3-0.9 

m) and 1” wide (2.5 cm). They are often recurved and have rough margins and 

a prominent whitish midvein. The ligules and stem nodes are membranous and 

fringed with hairs. The inflorescence resembles a corn tassel and is pyramid- to 

fan-shaped, up to 1’ long (30 cm), and occurs at stem tips in late summer/early 

fall. Florets do not have awns. Mature seeds are covered in silky hairs, giving the 

mature inflorescence a fluffy, silver appearance. 

REPRODUCTION: Spreads by seed and rhizomes. Seeds typically remain viable 

for less than five years. 

a b

Amur silvergrass a. plants; b. infestation (a,b. Leslie Mehrhoff, University of Connecticut bugwood.org)
New Invaders of the Northeast and Northcentral United States 15

Family Poaceae

c d e

Amur silvergrass c. leaf blade with white midvein and stems with hairy nodes and ligules; d. flowering 

inflorescence; e. mature inflorescences (c-e. Leslie Mehrhoff, University of Connecticut, bugwood.org)

HABITAT: Amur silvergrass grows best in moist, disturbed areas in full sun to 

partial shade. It can be found along roadside ditches, woodland borders, field 

margins, and pond edges.

LOOK-ALIKES: Several native and exotic grasses 

resemble Amur silvergrass. The clumped but 

rhizomatous growth, hairy ligules, and white 

midveins help differentiate Amur silvergrass from 

jubata and pampas grass (Cortaderia jubata and 

C. selloana). The similar rhizomatous and lineargrowing giant and common reeds (Arundo donax

and Phragmites australis, respectively) both grow 

taller than Amur silvergrass and both are not as 

hairy at nodes and ligules. The closely related 

exotic Chinese silvergrass (Miscanthus sinensis) has 

wider and less upright inflorescences. The exotic 

Ravenna grass (Saccharum ravennae) has many 

similar traits but differs in that its roots are fibrous, 

its leaf bases are covered in much denser hairs, and 

it grows much taller with longer inflorescences. 

NOXIOUS WEED LISTINGS: MA (Prohibited)

NOTES: This species is frequently used for soil 

erosion control and as an ornamental, but often escapes cultivation. A sterile 

cross of this species and Chinese silvergrass (Miscanthus sinensis) is being studied 

for its biofuel potential.

Look-alike: Chinese silvergrass 

(Leslie Mehrhoff, University of 

Connecticut, bugwood.org)
16 New Invaders of the Northeast and Northcentral United States GREEN FLOWERS

Feathertop

Calamagrostis epigejos (L.) Roth

SYNONYMS: wood small-reed, chee reed grass, Arundo epigejos L., C. epigeios (L.) Roth

ORIGIN: Africa, Asia, Europe

GROWTH TRAITS: Perennial grass with flowering stems reaching 2-6.5' (60-

200 cm) tall from a rhizomatous root system. Stems are hollow between nodes. 

Leaf blades are alternate, drooping, up to 28" (70 cm) long by 0.5" (12 mm) 

wide, green, with ribbed and rough upper surfaces. On the interior surface of 

the leaf where it meets the stem is a papery, triangular ligule 0.16-0.5" (4–12 

mm) long. Florets occur on dense, branched inflorescences 6-12" (15-30 cm) 

long throughout summer. At maturity, inflorescences are a rich brown or tinged 

with purple. Each floret is enclosed by 2 narrow, pointed bracts 0.2-0.28" (5-7 

mm) long. These gape open to reveal 2 narrow shorter bracts, the reproductive 

parts, and a mass of fine, white hairs. New stems sprout from rhizomes in spring. 

REPRODUCTION: Spreads by seed and rhizomes. Seeds remain viable in the 

soil for at least five years. 

a b

Feathertop a. plants; b. infestation (a. Christian Fischer; b. Лобачев Владимир)
New Invaders of the Northeast and Northcentral United States 17

Family Poaceae

c d e f

Feathertop c. leaf blade and stem node; d. ligule, stem, and base of leaf blade; e. inflorescence; f. 

floret (c,d,f. © Hermann Falkner; e. © Samuel Brinker, iNaturalist.org)

HABITAT: Feathertop can tolerate a wide variety of conditions including moist, 

brackish soil and dry conditions. It can be found escaping cultivation along 

fields, roadsides, and other disturbed places and also invading meadows and 

forest clearings.

LOOK-ALIKES: Native bluejoint (Calamagrostis 

canadensis) is very similar to feathertop, but it 

grows somewhat shorter with a smaller, narrower, 

less-dense inflorescence and narrower leaves. The 

ligule of bluejoint is also shorter (up to 0.16" or 

4 mm long) and more flat at its tip. The native 

slimstem reedgrass (C. stricta) is also very similar 

but has even smaller features than bluejoint. 

Slimstem reedgrass is also typically a wetland 

species.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: This species is sometimes cultivated as an 

ornamental grass, and is also used in revegetation 

and erosion control.

Look-alike: bluejoint 

(Lazaregagnidze)
18 New Invaders of the Northeast and Northcentral United States GREEN FLOWERS

Golden & Yellow groove bamboo

Phyllostachys aurea Carr. ex A.& C. Rivière & P. aureosulcata McClure

a

b c

d

Golden bamboo a. plant; b. joints; c. stem with compressed basal internodes; d. leaves (a. Nancy 

Loewenstein, Auburn University; b. Chuck Bargeron, University of Georgia; c. David Stephens; d. 

James H. Miller, USDA FS; a-d. bugwood.org)

e

f g

h

Yellow groove bamboo e. plants; f. stem close-up (yellow groove is faint due to thickness/age of 

mature stems); g. several stems; h. leaves (e,h. Daderot; f. Caryn Rickel, bugwood.org; g. Yongxinge)
New Invaders of the Northeast and Northcentral United States 19

Family Poaceae

SYNONYMS: Golden bamboo (GB): fish-pole bamboo; Yellow groove bamboo (YGB): 

stake-and-forage bamboo, Phyllostachys aureosulcata f. spectabilis C. D. Chu & C. S. Chao

ORIGIN: GB: China, Taiwan; YGB: China

GROWTH TRAITS: Both species are giant, perennial grasses that resemble 

narrow trees with thin side branches. They typically grow 16-40' (5-12 m) tall 

from spreading, rhizomatous root systems. Stems are woody, hollow with solid 

joints (nodes), and typically 1-3.5" (2.5-9 cm) in diameter, though some grow 

to 6" (15 cm). Leaves are lance-shaped with long petioles. Flowering is rare for 

both species. Plants are evergreen; old leaves are gradually replaced by new ones 

late in spring. In very severe winters, stems may die back and be replaced by new 

shoots in spring. GB: Stems are generally green but turn yellow when exposed 

to full sun. Basal stem joints are closer together than joints further up the stem, 

resulting in compressed "internodes". Leaves are 3-6" (7.5-15 cm) long. YGB: 

Young stems are rough-feeling and deep green with a yellow groove on every 

other internode. The rough texture decreases, and the stem colors fade with age. 

Leaves are 3-7" (7.5-17.5 cm) long. 

REPRODUCTION: Both species spread primarily via rhizomes. 

HABITAT: Both species do best in full sun but can tolerate partial shade and are 

typically found on roadsides, hillsides, and spreading from old home sites where 

they were intentionally planted. Both species are very cold tolerant. 

LOOK-ALIKES: Several similar species of Phyllostachys bamboo (all exotic) have 

been intentionally introduced to North America as ornamentals or for timber 

products. The compressed internodes of golden bamboo and the yellow stem stripe 

of yellow groove bamboo help differentiate these species from other bamboos and 

from each other. A few species of cane (Arundinaria) are native to North America. 

They differ from exotic bamboos by typically growing smaller and thinner.

NOXIOUS WEED LISTINGS: Both species: NY (Prohibited)

NOTES: Both species were 

introduced to the USA 

for their ornamental 

value and have been 

used in sound barriers 

and as fishing poles. golden bamboo yellow groove bamboo
20 New Invaders of the Northeast and Northcentral United States GREEN FLOWERS

Ravenna grass

Saccharum ravennae (L.) L.

SYNONYMS: hardy pampas grass, elephant grass, plume grass, Erianthus 

ravennae (L.) Beauv., Andropogon ravennae L., Ripidium ravennae (L.) Trin., 

Tripidium ravennae (L.) H. Scholz

ORIGIN: Eurasia, the Mediterranean

GROWTH TRAITS: Perennial bunchgrass growing 8-13’ (2.4-4 m) tall from 

a densely fibrous root system. Leaves are basal and also distributed up the stem 

to the bottom of the inflorescence. Leaves have serrated margins, a thick, white 

midvein on the upper sides of blades, and can be 1.6-3.3' (0.5-1 m) long and 

0.5” (1.2 cm) wide. Leaf bases are unlobed and are densely covered with long, 

fuzzy hairs that typically hide the ligule. Dense flower plumes are purplish 

(maturing to silver to tan), up to 2’ (0.6 m) long, and bloom from July through 

October. Florets are covered in tufts of silky hairs, giving the inflorescence an 

overall fluffy appearance. 

a b

Ravenna grass a. plant; b. infestation (a. Jennifer Andreas, Washington State University Extension; 

b. The Nature Conservancy Archive, The Nature Conservancy, bugwood.org)
New Invaders of the Northeast and Northcentral United States 21

Family Poaceae

c d e

Ravenna grass c. leaf blade with serrated margins and white midveins; d. hairy leaf base; 

e. inflorescences (c-e. Wendy DesCamp, Washington State Noxious Weed Control Board)

REPRODUCTION: Spreads by seed. Seed longevity is unknown but believed 

to be only a few years. 

HABITAT: Ravenna grass can be found in open, 

disturbed locations such as roadsides and field 

margins at both moist and dry sites, and it is 

tolerant of cold weather.

LOOK-ALIKES: Several native and exotic grasses 

resemble Ravenna grass. The clumped bunches help 

differentiate Ravenna grass from the rhizomatous 

and linear-growing giant and common reeds (Arundo 

donax and Phragmites australis, respectively). Jubata 

and pampas grass (Cortaderia jubata and C. 

selloana) are similar-looking bunchgrasses, but both 

lack hairs at leaf and stem bases, their leaf margins are much sharper, and their leaf 

midveins are not thick and white on the upper sides of the blades. Most native 

plumegrass species (Saccharum) have much more compact inflorescences. Giant 

plumegrass (S. giganteum) and shortbeard plumegrass (S. brevibarbe) inflorescences 

may be open, but both species typically grow shorter than Ravenna grass with 

overall smaller features, and their leaf bases are far less hairy.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: This species is frequently used for soil 

erosion control and as an ornamental, but often 

escapes cultivation.

Look-alike: common reed 

(Andy.vac)
22 New Invaders of the Northeast and Northcentral United States GREEN FLOWERS

Wavyleaf basketgrass

Oplismenus undulatifolius (Ard.) P. Beauv.

SYNONYMS: Oplismenus hirtellus ssp. undulatifolius (Ard.) U. Scholz

ORIGIN: southern Europe, southern Asia

GROWTH TRAITS: Perennial, low-growing grass reaching only 8-12" (20-30 

cm) tall from a shallow root system. Stems are stoloniferous and branch and 

root at lower nodes. Leaf blades are alternate, 1.5-4" (4-10 cm) long by 0.5" 

(1.3 cm) wide, elliptical, elongate, and sharply pointed. Leaves are a rich green 

with undulating ripples across their surface, resulting in the common name of 

"wavyleaf". Small hairs are scattered on both leaf surfaces; stem and node hairs 

are longer (up to 0.16" or 4 mm) and more dense. Flowering stems may be up 

to 20" (50 cm) tall and produce delicate-looking inflorescences from August 

through November. Florets are pinkish and have long, sticky awns that readily 

adhere to animals and people, aiding in dispersal. Leaves remain green through 

late fall, dying back over winter. New stems sprout from stolons in spring. 

a b

Wavyleaf basketgrass a. plants; b. infestation (a. Dalgial; b. Kerrie L. Kyde, Maryland Department 

of Natural Resources, bugwood.org)
New Invaders of the Northeast and Northcentral United States 23

Family Poaceae

c d e

Wavyleaf basketgrass c. leaf blades; d. hairy branching, rooting stems and stolon; e. inflorescence 

(c. Kerrie L. Kyde, Maryland Department of Natural Resources, bugwood.org; d. Garrett 

Waugaman, M-NCPPC Weed Warriors, bugwood.org; e. Yasunori Koide)

REPRODUCTION: Spreads by seed and stolons. Seeds remain viable in the soil 

for up to five years. 

HABITAT: Wavyleaf basketgrass grows best in moist 

soil in full shade to partial sun, allowing it to thrive 

under forest canopies where it forms dense mats 

covering forest floors.

LOOK-ALIKES: Native bristle basketgrass 

(Oplismenus hirtellus) is very similar, but its stems 

have few if any hairs, and its inflorescence branches 

are longer and have more florets that are a deeper 

purple. The native deer-tongue (Dichanthelium 

clandestinum) has similar hairy stems and sometimes 

rippled leaves, but it grows taller and in clumps. The 

exotic small carpetgrass (Arthraxon hispidus) has lowgrowing hairy stems and sometimes rippled leaves, 

but its leaves are heart-shaped at their base and clasp 

the stem.

NOXIOUS WEED LISTINGS: NY (Prohibited), 

WI (Prohibited)

NOTES: First discovered in Maryland in 1996, this species is spreading rapidly. 

There is currently taxonomic uncertainty with this group. Some taxonomic sources 

refer to wavyleaf basketgrass as a subspecies of the native Oplismenus hirtellus, while 

others (including those used for this guide) consider it a separate species.

Look-alike: bristle basketgrass. 

(Forest & Kim Starr, Starr 

Environmental)
24 New Invaders of the Northeast and Northcentral United States GREEN FLOWERS

Japanese chaff flower

Achyranthes japonica (Miq.) Nakai

SYNONYMS: Oriental chaff flower, Achyranthes bidentata var. japonica Miq.

ORIGIN: East Asia

GROWTH TRAITS: Herbaceous, upright perennial typically growing 1.6-6.6' 

tall (1⁄2-2 m) from a well-developed but non-rhizomatous root system. Young 

plants have one stem, while older plants have multiple stems arising from the 

same root crown. Stems are thin, wiry, 4-angled, branched, and often purpletinged at their slightly swollen nodes. Leaves are opposite, elliptical, and have 

prominant veins and smooth (sometimes wavy) margins. Leaves are 4-8” long 

(10-20 cm), gradually becoming smaller up the stem. Leaves and stems are 

slightly hairy. Flowers are produced from late summer to early fall. They are tiny 

with no petals and 5 green stamens. Flowers initially occur in tight clusters on 

spikes at branch and stem tips, but as fruits appear, spikes elongate significantly. 

Flowers diverge at nearly a 90° angle from the spike, but as fruits mature they 

lay flat (downwards) against the spike. The fruits are slender and dry with a 

single hard seed, and have a pair of stiff bracts arising from their base.

a b

Japanese chaff flower a. plant; b. infestation (a,b. Chris Evans, University of Illinois, bugwood.org)
New Invaders of the Northeast and Northcentral United States 25

Family Amaranthaceae

c d e

Japanese chaff flower c. leaves; d. flowers; e. mature fruit and hairy stem (c-e. Chris Evans, 

University of Illinois, bugwood.org)

REPRODUCTION: Spreads by seed. Seeds have very high germination rates, 

though longevity is unknown.

HABITAT: Usually found in partial shade and moist soil, but it will also grow 

in drier areas in both sunny and densely-shaded habitats. Often found in 

bottomland forests, along waterways and roadsides, and at the edges of fields.

LOOK-ALIKES: Several related pigweed species 

(Amaranthus) are present in North America and 

have similar flowers and reddish stems. However, 

they have alternate leaves, unlike the opposite 

leaves of Japanese chaff flower. The native bloodleaf 

(Iresine rhizomatosa), American lopseed (Phryma 

leptostachya), and swamp verbena (Verbena hastata) 

all have opposite leaves and similar fruit. Bloodleaf 

has tiny white flowers with papery-white petals, 

and female flowers have tufts of hairs at their base. 

American lopseed and swamp verbena leaves are 

toothed, and their flowers have true petals with 

pinkish-white and purple petals, respectively. American lopseed is most similar 

in fall/winter but can be differentiated by its bracts arising from fruit tips instead 

of the fruit base as in Japanese chaff flower.

NOXIOUS WEED LISTINGS: NY (Prohibited), 

WI (Prohibited)

NOTES: The pair of stiff bracts on the fruits aid in 

dispersal by readily attaching to clothes or fur.

Look-alike: swamp verbena 

(© Gerald D. Carr 2017)
26 New Invaders of the Northeast and Northcentral United States GREEN FLOWERS

Spiny emex

Rumex spinosus L.

SYNONYMS: devil's thorn, spiny threecorner Jack, prickly doc, Emex spinosa 

(L.) Campd.

ORIGIN: the Mediterranean

GROWTH TRAITS: Herbaceous annual that germinates in autumn or winter 

and grows 12-24” (30-60 cm) tall from a long, thick taproot. Stems are round, 

ridged, sometimes reddish, often somewhat sprawling, and branch periodically. 

Leaves are alternate, smooth, triangular to egg-shaped, 2-5” long (5-12.5 cm), and 

have slightly wavy margins. Leaves become increasingly smaller up the stem. Leaf 

stalks are long, hairless, and with membranous sheaths (ochreae) at their bases. 

Flowering occurs from early summer to winter with separate male and female 

flowers occurring on the same plant. Male flowers are small, inconspicuous, 

green, and occur in short clusters on stalks. Female flowers are spiny, without 

stalks, and occur in clusters around leaf axils. Fruits are produced on the stem and 

root crown. Stem fruits are triangular and green when young, turning reddishbrown, hardened, and with 3 sharp spines at maturity. Spines are up to 0.11” (3 

a b

Spiny emex a. plant; b. infestation (a,b. Forest & Kim Starr, Starr Environmental)
New Invaders of the Northeast and Northcentral United States 27

Family Polygonaceae

c d e f

Spiny emex c. leaves; d. male flowers; e. immature fruits; f. mature fruits (c,d. Forest & Kim Starr, 

Starr Environmental; e. Rolf Engstrand; f. Julia Scher, USDA APHIS PPQ, bugwood.org)

mm) long. Fruits on the root crown are larger but less spiny. These are yellowishred but turn brown with maturity. Each fruit contains a single glossy seed. When 

the plant dies back, its drying root pulls the crown seeds into the soil.

REPRODUCTION: Spreads by seed. Seeds remain 

viable in the soil for at least eight years.

HABITAT: Tolerates a wide variety of conditions 

but does best with disturbance. It is typically found 

along roadsides, railways, flood zones, field edges, 

pastures, grasslands, and other dry or sandy locations 

and can tolerate drought and cold temperatures.

LOOK-ALIKES: While various native and exotic 

species have similar triangular wavy leaves, ochreae, 

non-showy male flower clusters, or spiny female 

flowers clustered around leaf axils, the combination 

of all of these traits helps differentiate spiny emex 

from most look-alikes. The closest relative of spiny 

emex (the exotic southern threecorner Jack, Rumex 

hypogaeus) is very similar but has larger spiny fruits, 

smaller leaves, and tends to grow more prostrate 

than spiny emex.

NOXIOUS WEED LISTINGS: MA (Prohibited), RI (Noxious), VT (B), WV

NOTES: The spiny fruits readily adhere to clothing/shoes, fur, and equipment, 

aiding in the weed's dispersal.

Look-alike: southern 

threecorner Jack (Kevin Thiele)
28 New Invaders of the Northeast and Northcentral United States GREEN FLOWERS

Fragrant clematis & Traveler's joy

Clematis flammula L. & C. vitalba L.

a

b c

d

Fragrant clematis a. vines; b. leaves and leaflets; c. flowers; d. mature fruits (a. Peganum; b. © 

Drepanostoma, iNaturalist.org; c. © Jakob Fahr, iNaturalist.org; d. Mathieu Caunes)

e

f g

h

Traveler's joy e. vines; f. leaf and leaflets; g. flowers; h. mature fruits (e,g. Robert Vidéki, Doronicum 

Kft., bugwood.org; f. Hectonichus; h. Isidre blanc)
New Invaders of the Northeast and Northcentral United States 29

Family Ranunculaceae

SYNONYMS: Fragrant clematis (FC): fragrant virgin's bower; Traveler's joy 

(TJ): evergreen clematis, old man's beard

ORIGIN: Eurasia, the Mediterranean (both species)

GROWTH TRAITS: Both species are perennial climbing vines growing from 

fine, branched root systems. Vines (stems) are pliable when young, becoming 

woody with stringy bark. Vines smother trees, shrubs, walls, utility poles, etc. 

by climbing with tendril-like petioles. Vines grow erect between holds; where 

they grow along the ground, they root from nodes. Leaves are compound, green, 

opposite, and deciduous in cold climates. Leaflets are variable and may have 

either smooth margins or a few rounded teeth. Flowers are fragrant with 4 showy, 

white, petal-like sepals and numerous white stamens. Flowers occur in clusters 

at stem tips or in leaf axils in late summer. The fruit consists of numerous small 

seeds, each with a long feathery tail up to 1.2” long (3 cm) that give the fruits a 

pom-pom appearance. Fruits persist on vines throughout much of winter. FC: 

Vines can grow up to 20' (6 m) long. Leaves are dark green, glossy, typically twice 

compound, and split into 5-9 leaflets that are each 0.8-2" (2-5 cm) long. Flowers 

(profuse) are 0.8-1.2" (2-3 cm) across with narrow petal-like sepals. Seeds are 

strongly compressed and 0.2-0.24" (5-6 mm) long. TJ: Vines can grow up to 66' 

(20 m) long. Each leaf has 5 lance-shaped leaflets 1.2-4" (3-10 cm) long. Flowers 

are 0.8" (2 cm) across. Seeds are bulbous and 0.08-0.12" (2-3 mm) long.

REPRODUCTION: Both species spread by seed, rooting stems/segments, and 

sprouting from root crowns. Seeds may remain viable in the soil for up to 5 years.

HABITAT: Both species can be found along open sunny roadsides, riparian 

corridors, rocky slopes, fencerows, and in/along partially shaded woodlands. 

LOOK-ALIKES: FC grows shorter, has more flowers with narrower sepals, smaller 

and glossier leaflets, and larger but compressed seeds compared to TJ. Many other 

Clematis spp. differ with their yellow or purple flowers. The native virgin's bower (C. 

virginiana) has 3 leaflets with coarse teeth. The exotic Japanese clematis (C. terniflora) 

has compressed seeds 

with less feathery tails.

NOXIOUS WEED: 

Neither species is listed 

as noxious in any NE/

northcentral state. fragrant clematis traveler's joy
30 New Invaders of the Northeast and Northcentral United States GREEN FLOWERS

Amur corktree

Phellodendron amurense Rupr.

SYNONYMS: Japanese corktree, Chinese corktree, Phellodendron japonicum

Maxim.

ORIGIN: temperate Asia

GROWTH TRAITS: Deciduous tree typically growing 30-50' (9-15 m) tall from 

a shallow, but wide-spreading root system. Trees have short, straight trunks that 

divide into numerous spreading branches to form a rounded but wide canopy. 

Outer bark is grayish-brown, soft, and corky, becoming more rough-textured and 

furrowed with age. Inner bark is bright yellow. Leaves are opposite and divided 

into 5-13 leaflets that are 2.5-5" (6.4-12.7 cm) long. Leaflets are lance-shaped 

to elliptical and have very slightly toothed margins that often appear smooth 

from a distance. Leaves are bright green throughout summer and turn yellow 

in autumn. Flowers are yellow-green (sometimes maroon), non-showy, less than 

0.12" (3 mm) in diameter, and appear in loose clusters among leaves in late 

spring to early summer. Fruits are spherical, 0.4" (1 cm) across, berry-like, and 

a b

Amur corktree a. tree; b. bark (a. Isfisk; b. Chris Evans, University of Illinois, bugwood.org)
New Invaders of the Northeast and Northcentral United States 31

Family Rutaceae

c d e

Amur corktree c. leaves; d. flowers; e. autumn foliage and fruits (c. Anneli Salo; d. Ettrig; e. Kurt Stüber)

green, turning black at maturity. Fruits remain on the tree through early winter. 

Crushed foliage and fruits are odorous, variously described as turpentine-like, 

skunk-like, or citrusy. Individuals are long-lived under some conditions.

REPRODUCTION: Spreads by seed. Seeds remain viable for several years.

HABITAT: Tolerates many soil types, though it 

does best in well-drained soil with a lot of organic 

material and in full sun. In North America, it has 

been found invading forest edges, canopy gaps, and 

areas of human disturbance, but can also persist in 

the understory of closed-canopy forests.

LOOK-ALIKES: The combination of yellow inner 

bark, opposite leaves, non-showy yellow-green 

flowers, berry-like odorous fruit help differentiate 

this species from most potential look-alikes. While 

other species may have a few similar features (such 

as the opposite, compound leaves of native Fraxinus

or ash species), no other species exhibit all of these traits.

NOXIOUS WEED LISTINGS: MA, NY, WI (all 

Prohibited), ME

NOTES: Amur corktree is a popular ornamental 

shade tree (male clones) that was introduced 

intentionally into the USA in 1865.

Look-alike: black ash (Keith 

Kanoti, Maine Forest Service, 

bugwood.org)
32 New Invaders of the Northeast and Northcentral United States GREEN FLOWERS

Japanese zelkova

Zelkova serrata (Thunb.) Makino

SYNONYMS: Japanese elm, zelkova

ORIGIN: Asia

GROWTH TRAITS: Deciduous tree typically growing 50-80' (15-24 m) tall from 

a deep root system. Trees have short trunks that divide into numerous erect branches 

to form a vase-shaped crown. The bark is grayish-brown and porous. At maturity, 

patches of bark begin to peel, revealing orangish bark beneath. Leaves have distinct 

veins and toothed margins, and are ovate, symmetrical, and alternately attached 

to the branch with petioles 0.08-0.2" (2-5 mm) long. Most leaves are up to 2" (5 

cm) long, though some may be up to 4" (10 cm). Leaves are pale to dark green 

throughout summer and turn yellow, orange, or red in autumn. Buds diverge from 

branches at 45° angles, resulting in a zig-zag appearance. Flowers are yellow-green, 

non-showy, less than 0.12" (3 mm) in diameter, and appear in tight clusters along 

new stems in spring before new leaves emerge. Fruits are triangular to oval-shaped, 

0.12" (3 mm) across, berry-like, and green, turning brown at maturity. Individuals 

can live for hundreds of years under some conditions.

a b

Japanese zelkova a. tree; b. bark (a. Bruce Marlin; b. Geographer)
New Invaders of the Northeast and Northcentral United States 33

Family Ulmaceae

c d e

Japanese zelkova c. leaves; d. flowers and foliage; e. fruits (c. Steven J. Baskauf, bioimages.vanderbilt.

edu; d. Kenpei; e. © Virginia Tech Department of Forest Resources and Environmental Conservation,

http://dendro.cnre.vt.edu/dendrology/)

REPRODUCTION: Spreads by seed. Seeds may remain viable for up to four 

years.

HABITAT: Tolerates most soil types, though it does 

best in moist, deep, loamy soil in full to partial 

sun. It is typically found along forest edges and 

roadsides and in moist ravines, riparian areas, 

abandoned lands, and urban gardens. Established 

trees are fairly drought-tolerant, unless growing in 

sandy soils.

LOOK-ALIKES: The alternate, deeply toothed 

and veined leaves, divergent buds, and non-showy 

flowers help differentiate this tree from many 

unrelated look-alikes. Within the family, several 

native and exotic elms (Ulmus spp.) resemble 

Japanese zelkova with their similar leaves, flowers, bark, and growth form. Elms 

can be differentiated by having asymmetrical leaf bases and winged fruits.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: Japanese zelkova is a popular ornamental 

species with numerous cultivars available and 

used in yards and urban landscapes. It is highly 

resistant to Dutch elm disease, which has ravaged 

populations of native American elm.

Look-alike: American elm 

leaf (Paul Wray, Iowa State 

University, bugwood.org)
34 New Invaders of the Northeast and Northcentral United States GREEN FLOWERS

Paper mulberry

Broussonetia papyrifera (L.) Vent.

SYNONYMS: tapa cloth tree, Morus papyrifera L.

ORIGIN: Asia

GROWTH TRAITS: Fast-growing, deciduous tree typically reaching 30-50' (9-

15 m) tall from a shallow root system. Trees have short, straight trunks that 

divide into stout spreading branches to form a rounded canopy. Branches are 

brittle and susceptible to wind damage. Branches may appear fuzzy when young; 

older bark is grayish-brown with shallow fissures. Leaves are alternate (some 

appear close to opposite), 3-10" (7.5-25 cm) long, and variable. Leaves varying 

from ovate and unlobed to mitten-shaped with deep lobes often appear on the 

same shoot. All leaves are typically hairy on both sides and have finely toothed 

margins. Milky sap is exuded from damaged tissue. Male and female flowers 

appear on different plants in spring. Male flowers are tiny, yellow-green, and 

appear in narrow catkins up to 3" (7.5 cm) long. Female flowers are non-showy 

and green, appearing on spherical heads and each trailing a long, pink threadlike 

a b

Paper mulberry a. tree; b. bark (a. Chuck Bargeron, University of Georgia; b. James H. Miller, 

USDA Forest Service; a,b. bugwood.org)
New Invaders of the Northeast and Northcentral United States 35

Family Moraceae

c d e f

Paper mulberry c. variable leaves; d. male inflorescences; e. female inflorescences; f. fruit (c. Didier 

Descouens; d. Cillas; e. Daderot; f. Yug)

floral part. Numerous fleshy, orangish-red fruits appear around spherical 

pendants 1.2" (3 cm) across. Cultivated individuals may live 25-50 years under 

some conditions.

REPRODUCTION: Spreads by seed and suckering 

from the root system. Seed longevity is unknown.

HABITAT: Does best in moist soil and full sun. In 

North America, it has been found invading forest 

edges and gaps, floodplains, river terraces, old 

fields, and other areas of human disturbance. 

LOOK-ALIKES: The combination of hairy twigs 

and leaves, variable leaves, male and female flowers 

appearing on separate trees, and the fleshy globular 

fruits helps differentiate paper mulberry from many 

potential look-alikes. The exotic white mulberry 

(Morus alba) has leaves with larger teeth and its 

fruits resemble raspberries or blackberries rather 

than spheres. The fruits of the native red mulberry 

(M. rubra) resemble cylindrical raspberries.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: Paper mulberry was intentionally introduced to North America as a 

fast-growing ornamental shade tree. In Asia, it has been used in paper-making. 

In Hawaii and parts of the South Pacific, its bark has been used to make cloth. 

Look-alike: white mulberry 

(Vladimer Shioshvili)
36 New Invaders of the Northeast and Northcentral United States PINKISH PURPLE FLOWERSHimalayan balsam

Impatiens glandulifera Royle

SYNONYMS: ornamental jewelweed, policeman’s helmet, Impatiens roylei Walp.

ORIGIN: India

GROWTH TRAITS: Herbaceous annual growing 3-10’ (0.9-1 m) tall from a 

shallow, fibrous root system. Stems are smooth, hairless, sharply angled, hollow, 

and often have a purplish tinge. Leaves are elliptical or lance-shaped with narrow 

tips, 2-9” (5-23 cm) long, and either opposite or in whorls of 3. Leaves have 

serrated margins and glandular stalks at their bases. Flowers appear from June 

to October on flower stalks in clusters at leaf nodes and stem tips. Flowers vary 

from white to deep pink, are ~1.3” tall (3-4 cm), and have 5 petals. Some of the 

petals are fused, giving the flower a unique shape resembling an old-fashioned 

English policeman’s helmet. Seed pods are green, elongated teardrop-shaped, 

and 0.75-1.25” (2-3 cm) long. Seed pods explode when disturbed, scattering the 

small brown seeds up to 23’ (7 m).

a b

Himalayan balsam a. plant; b. infestation (a. Udo Schmidt; b. Wassily)
New Invaders of the Northeast and Northcentral United States 37

Family Balsaminaceae

c d e f

Himalayan balsam c. leaves and stem; d. stem and glandular stalks at leaf base; e. flower and fruit; 

f. mature and exploded seed pods (c. Markus Nolf; d. Leslie J. Mehrhoff, University of Connecticut, 

bugwood.org; e. Barbara Tokarska, Guzik University of Silesia, bugwood.org; f. Rasbak)

REPRODUCTION: Spreads by seed. Seeds may remain viable in the soil for up 

to 18 months. 

HABITAT: Grows in partial shade to full sun in 

moist soil. It is regularly found in moist areas 

including woodlands, forest clearings, streambanks, 

meadows, and roadsides where water collects..

LOOK-ALIKES: Many native and exotic species 

of Impatiens resemble Himalayan balsam. Most 

look-alike relatives have smaller leaves (frequently 

alternate) and/or flowers with different colors. The 

native orange jewelweed (I. capensis) has orange 

flowers while the native pale jewelweed (I. pallida) 

has yellow flowers. Fireweed (Chamaenerion 

angustifolium, previously Epilobium angustifolium) is an unrelated native species 

that has similar leaves and deep pink flowers. However, petals of fireweed are 

not fused, and its leaves are alternate. The exotic hairy willowherb (Epilobium 

hirsutum) is also similar, but its flowers are more solitary and have 4 notched, 

unfused, and overlapping petals.

NOXIOUS WEED LISTINGS: CT, NH, WI (all 

Prohibited), ME (Noxious)

NOTES: This species is frequently sold as an 

ornamental and quickly escapes cultivation.

Look-alike: fireweed (Kallerna)
38 New Invaders of the Northeast and Northcentral United States PINKISH PURPLE FLOWERSMilk thistle

Silybum marianum (L.) Gaertn.

SYNONYMS: blessed milkthistle, variegated thistle, Carduus marianus L., 

Mariana mariana (L.) Hill

ORIGIN: Eurasia, the Mediterranean

GROWTH TRAITS: Herbaceous winter annual or biennial growing 2-6' (0.6-1.8 

m) tall from a long taproot. Rosettes form either in fall and overwinter, or they grow 

in spring. Stems bolt in later spring and are stout, rigid, and not spiny along their 

entire length. Leaves are deeply lobed, dark green, variegated with white markings 

along veins, and have spiny margins. Rosette leaves are up to 20” (50 cm) long; 

stem leaves are alternate, clasp the stem, and are much smaller, decreasing in size 

further up the stem. Flower heads are up to 2” (5 cm) in diameter and are solitary 

at the ends of stems. The bases of flower heads (receptacles) have rows of broad, 

leathery bracts tipped with very stiff spines fringed with smaller spines. Florets 

are magenta to purple and appear from May to August. Flower heads produce 

numerous brown or black seeds with a tuft of silky hairs at their tips. 

a b

Milk thistle a. plant; b. infestation (a. Eric Coombs, Oregon Department of Agriculture; b. Jan 

Samanek, Phytosanitary Administration; a,b. bugwood.org)
New Invaders of the Northeast and Northcentral United States 39

Family Asteraceae

c d e

Milk thistle c. rosette leaves; d. flower head; e. senescing flower head and seeds (c,d. Eric Coombs, 

Oregon Department of Agriculture, e. Joseph M. DiTomaso, University of California - Davis; c-e. 

bugwood.org)

REPRODUCTION: Spreads by seed, which may remain viable for up to 9 years. 

HABITAT: Grows best in full sun and in soils with high fertility and disturbance, 

including overgrazed pastures, roadsides, ditches, waste areas, and stockyards.

LOOK-ALIKES: Over 80 native thistle species 

and more than 20 exotic thistles occur in North 

America, and all resemble milk thistle to some 

extent. The variegated leaves and large flower heads 

with broad, leathery, spiny bracts help differentiate 

milk thistle from potential look-alike thistle 

species. The exotic musk thistle (Carduus nutans)

has similar large flower heads and leaves, but its 

bracts are shorter and not leathery, and its leaves 

are only white along their margins.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: This species is sometimes used in site 

remediation projects as it is capable of removing large amounts of lead, nitrates, and zinc from 

polluted soil. While all milk thistle plants are 

considered toxic to livestock, plants growing in 

polluted areas are especially toxic. Milk thistle is an ancient medicinal plant 

used in the treatment of liver disorders and is still sold by a number of garden 

seed suppliers in the USA.

Look-alike: musk thistle (Mary 

Ellen (Mel) Harte, bugwood.org)
40 New Invaders of the Northeast and Northcentral United States PINKISH PURPLE FLOWERSRagged robin

Silene flos-cuculi (L.) Greuter & Burdet

SYNONYMS: meadow campion, Lychnis flos-cuculi L.

ORIGIN: Europe, Eurasia

GROWTH TRAITS: Herbaceous perennial with upright flowering stems 

growing 8-31.5" (20-80 cm) tall from a shallow, fibrous root system. Stems are 

rigid, branched near their tips, and are covered in small, barbed, downwardpointing hairs that make the plant rough to the touch. Leaves are opposite, 

narrow, and have smooth margins. Basal leaves are wider at their tips while 

leaves further up the stem are more linear and lance-shaped with pointed tips. 

Flowers appear in small clusters at branch tips from May to August. Flowers are 

approximately 1.5" (3.8 cm) across and have 5 pink petals, each deeply divided 

into 4 lobes, giving the flower an untidy, ragged appearance. Flower bases are 

fused, appearing tubular. Fruits are small capsules 0.2-0.4" (6-10 mm) long that 

open at their tops to release several small seeds throughout fall. 

a b

Ragged robin a. plant; b. infestation (a. Stefan.lefnaer; b. Leslie Mehrhoff, University of 

Connecticut, bugwood.org)
New Invaders of the Northeast and Northcentral United States 41

Family Caryophyllaceae

c d e

Ragged robin c. basal leaves and stem; d. flowers; e. fruit (c-e. Leslie Mehrhoff, University of 

Connecticut, bugwood.org)

REPRODUCTION: Spreads by seed. Buried seeds may remain viable for at least 

five years. 

HABITAT: Grows best in full sun and in moist soil. It is regularly found in wet 

meadows and pastures, boggy areas, wetlands, and along irrigation ditches.

LOOK-ALIKES: The combination of opposite 

leaves, 5-petal flowers, and swollen tubular flower 

bases help differentiate ragged robin from most 

potential unrelated look-alikes. Within the family, 

several species of Silene occur in North America, 

and all resemble ragged robin to some extent. 

Ragged robin's pink petals that are deeply divided 

into four lobes each help differentiate it from its 

relatives. The exotic red catchfly (S. dioica) and 

sticky catchfly (S. viscaria) both have pink petals, 

but neither species has petals as deeply divided as 

ragged robin. The native fire pink (S. virginica) 

typically has red petals that are notched at the tips 

to form two sharp lobes.

NOXIOUS WEED LISTINGS: CT (Prohibited)

NOTES: This species was likely introduced to North 

America in the late 1800s both intentionally in 

garden plantings and accidentally via ship ballast.

Look-alike: red catchfly (Anneli 

Salo)
42 New Invaders of the Northeast and Northcentral United States PINKISH PURPLE FLOWERSChocolate vine

Akebia quinata (Houtt.) Decne.

SYNONYMS: fiveleaf, fiveleaf akebia

ORIGIN: China, Japan, Korea

GROWTH TRAITS: Perennial, twining vine with many stems growing from a 

rhizomatous root system. Vines are green when young, but at maturity become 

woody and grayish-brown with distinct lenticels. Vines are typically 26-49' (8-15 

m) long and can form a creeping groundcover or twine around adjacent vegetation 

and structures. Leaves have long petioles, are alternate, and divided into 5 leaflets 

all arising from the same point. Leaflets are bright to deep green, smooth, 0.5-3.1" 

(1.3-8 cm) long, oval, and have smooth margins, a rounded base, and a rounded 

but slightly notched tip. Flowers appear in hanging clusters from leaf axils in spring. 

Separate male and female flowers are produced in the same cluster; both lack petals 

but have 3 showy sepals ranging from white to deep purple. Male flowers are up to 

0.4" (1 cm) across with 6-7 incurved stamens. Female flowers are generally twice as 

large (0.8" or 2 cm across) and some may have a faint, sweet, chocolate odor. Fruits 

a b

Chocolate vine a. vine; b. infestation in forest understory (a. © Jeremy Rolfe; b. Chris Evans, 

University of Illinois, bugwood.org)
New Invaders of the Northeast and Northcentral United States 43

Family Lardizabalaceae

c d e

Chocolate vine c. leaves; d. large female flower and smaller male flowers; e. fruits (c. Chris Evans, 

University of Illinois, bugwood.org; d. Schurdl; e. Alpsdake)

are sausage-shaped pods up to 4" (10 cm) long that split at maturity, revealing 

white pulp and tiny black seeds. Flowers and fruit are uncommonly produced in 

the wild. In cold climates, plants die back in the fall and re-sprout from the root 

system in spring. At warm locations the plant can be evergreen. 

REPRODUCTION: Spreads by seed (uncommon), but most spread is vegetative 

via rhizomes and rooting from stems. Seed longevity is unknown.

HABITAT: Tolerates full sun and drought to shady, 

moist sites with cold winters. New growth may 

be frost sensitive. Grows best in moist but welldrained soil and readily invades hedgerows, forest 

understories and margins, streamsides, and hillsides.

LOOK-ALIKES: The compound leaves with 5 

leaflets arising from the same point may resemble 

the native vine Virginia creeper (Parthenocissus 

quinquefolia). Virginia creeper leaflets are toothed, 

and its fruits are bluish-black berries. The vine 

growth and hanging purple flowers also resemble 

native and exotic Wisteria species, but those differ 

in having leaflets arise opposite each other on a leaf 

stalk, rather than all from the same point.

NOXIOUS WEED LISTINGS: WI (Prohibited)

NOTES: The fruit is edible and has been used in 

traditional cuisine, while the vines were historically used for basket weaving.

Look-alike: Virginia creeper 

(Lazaregagnidze)
44 New Invaders of the Northeast and Northcentral United States PINKISH PURPLE FLOWERSJapanese spiraea

Spiraea japonica L. f.

SYNONYMS: Japanese meadowsweet

ORIGIN: China, Japan, Korea

GROWTH TRAITS: Rounded, deciduous shrub growing 4-6' (1.2-1.8 m) tall 

and equally wide from a fibrous root system. Stems are dense, slender, outwardarching, and branch predominantly from the base. Stems are brown to reddishbrown, round in cross-section, and sometimes hairy. Leaves are ovate or lanceshaped, alternate, 1-3" (2.5-7.5 cm) long, and have finely-toothed margins. 

Flowers appear in flat-topped clusters at branch tips from late spring to early 

summer. The tiny flowers have 5 rosy pink (sometimes white) petals. The fruits 

are inconspicuous, dry brown capsules that split open when ripe. Fruits often 

remain on branches through winter. 

REPRODUCTION: Spreads by seed, which may remain viable for many years. 

a b

Japanese spiraea a. shrub; b. infestation in forest understory (a. Jerzy Opioła; b. Nancy Dagley, 

USDI National Park Service, bugwood.org)
New Invaders of the Northeast and Northcentral United States 45

Family Rosaceae

c d e

Japanese spiraea c. leaves; d. flowers; e. fruits (c. James H. Miller, USDA Forest Service; d,e. Leslie J. 

Mehrhoff, University of Connecticut; c-e. bugwood.org)

HABITAT: Can tolerate a wide range of soil conditions and full sun to partial 

shade, but grows best in rich, moist soils in full sun. It readily invades forest 

understories and margins, bogs, streamsides, moist fields, and other disturbed 

sites.

LOOK-ALIKES: Several species of Spiraea present 

in North America closely resemble Japanese spiraea 

with their similar habitat, shrub shape, alternate 

leaves, and tightly clustered 5-petal flowers. Most 

potential look-alikes can be differentiated by 

having white petals. When varieties of Japanese 

spiraea have white petals, they differ from the exotic 

Thunberg's meadowsweet (Spiraea thunbergii) by 

having larger, thicker leaves and flowers occurring 

in flat-topped clusters instead of along branches. 

The native white meadowsweet (S. alba) has 

larger leaves, and its white flowers occur in large 

cone-shaped clusters. The native rose spiraea (S. 

douglasii) has pink flowers, but they appear in large cone-shaped clusters.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: This species is still popular in the ornamental 

trade, and many varieties are commercially available, 

leading to variability in plant traits.

Look-alike: rose spiraea 

(Meggar)
46 New Invaders of the Northeast and Northcentral United States PINKISH PURPLE FLOWERSShrub lespedeza

Lespedeza bicolor Turcz.

SYNONYMS: shrubby bushclover, bicolor lespedeza, two-colored bushclover

ORIGIN: Asia

GROWTH TRAITS: Highly variable species that can grow as a large forb or as an 

upright, deciduous shrub. Plants grow 3-10' (0.9-3 m) tall and equally wide from 

a dense, multi-branched root system. Stems are slender, arching, and have small 

roundish bumps at maturity. Leaves are alternate and divided into three leaflets. 

Leaflets are 0.75-2" (1.9-5 cm) long and typically elliptical on basal leaves, but 

lance-shaped on upper leaves. Leaflets are darker green on upper surfaces and 

lighter beneath, smooth-margined, and have a tiny hair-like tip. Flowers appear 

in upright, loose clusters at branch tips and from leaf axils throughout summer. 

Flowers are 0.5" (1.3 cm) long and pea-like (having a banner, wing and keel, 

typical of the pea family) with pinkish-purple petals. The fruits are flat, oval pods 

with long thin tips. They are 0.3" (8 mm) long and 1-seeded. Some cultivars are 

very winter hardy, while for others, entire stems or just stem tips can be winterkilled. Those individuals may re-sprout from the roots following winter damage.

a b

Shrub lespedeza a. shrub; b. infestation (a. © daniel_folds, iNaturalist.org; b. James H. Miller, 

USDA Forest Service, bugwood.org)
New Invaders of the Northeast and Northcentral United States 47

Family Fabaceae

c d e

Shrub lespedeza c. upper leaves (both surfaces); d. flowers; e. fruits (c. James H. Miller, USDA Forest 

Service; d. © Suzanne Cadwell; e. Karan A. Rawlins, University of Georgia; c,e. bugwood.org)

REPRODUCTION: Spreads by seed, but can also re-sprout from the root 

system following damage. Seeds may remain viable for over 20 years, possibly 

much longer. 

HABITAT: Grows well in full sun to partial shade. 

This species capitalizes on disturbance, but readily 

spreads into undisturbed areas. It is typically 

found in old fields, meadows, forest margins and 

clearings, and even closed woodlands. 

LOOK-ALIKES: The pea-like flowers, compound 

leaves, and oval pod fruit help differentiate shrub 

lespedeza from unrelated look-alikes. There are 

several native and exotic related Lespedeza species 

present in North America. Shrub lespedeza can be 

differentiated from many others that have white 

flowers, hairy foliage, and/or much narrower leaves. 

The exotic Thunberg's lespedeza (L. thunbergii) has 

similar leaves and pinkish-purple flowers, but its 

flower clusters typically droop, compared to the 

more upright flower clusters of shrub lespedeza.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: Shrub lespedeza was once widely planted for wildlife habitat, especially for 

northern bobwhite quail. It is no longer recommended for planting, and native 

plant species have since been recognized as superior for wildlife habitat.

Look-alike: Thunberg's 

lespedeza (BotBln)
48 New Invaders of the Northeast and Northcentral United States PINKISH PURPLE FLOWERSChinaberry tree

Melia azedarach L.

SYNONYMS: cape lilac, Persian lilac, pride-of-India, umbrella tree, white cedar

ORIGIN: Asia, Australia

GROWTH TRAITS: Deciduous tree typically growing 20-50' (6.1-15.2 m) tall 

but reaching heights of 150' (45 m) in exceptional circumstances. Trees grow from 

a shallow root system and usually produce one trunk (2' or 60 cm in diameter) 

that is multi-branched and forms a loose, straggly canopy. The bark of new 

branches is reddish-brown with distinct round lenticels, but becomes grayishbrown with longitudinal furrows with age. Leaves are alternate and attached to 

the branch with long petioles. Leaves are 1-2' (30-60 cm) long and two- or threetimes divided into 3-7 pairs of opposite leaflets. Leaflets are 1-3" (2.5-7.5 cm) 

long, ovate, elliptical, or obovate with toothed margins and prominent midveins. 

Leaves are green and turn yellow in autumn before falling to the ground for winter. 

Flowers appear in loose clusters from leaf axils in spring. Each flower is 0.7" (1.8 

cm) across, star-shaped, and has 5 pink to lilac petals. Flowers are fragrant and have 

a b

Chinaberry tree a. tree; b. bark with lenticels and fissures (a. Chuck Bargeron, University of 

Georgia; b. Karan A. Rawlins, University of Georgia; a,b. bugwood.org)
New Invaders of the Northeast and Northcentral United States 49

Family Meliaceae

c d e

Chinaberry tree c. leaflets; d. flowers; e. fruit (c. Karan A. Rawlins, University of Georgia; 

d. Chris Evans, University of Illinois; e. Franklin Bonner, USFS; c-e. bugwood.org)

purplish-red fringed centers. The clustered, spherical, berry-like fruits are 0.5" (1.3 

cm) wide and green at first but turn yellow at maturity. Some fruits remain on 

the trees through winter; others drop in the fall and can become safety hazards on 

sidewalks. Plants live 20 years on average, but some can live much longer.

REPRODUCTION: Spreads by seed but can also re-sprout from the root system 

following damage, creating dense thickets. Seeds are viable for up to two years.

HABITAT: Capitalizes on disturbance but then 

readily spreads into undisturbed areas. In North 

America, it can be found along roadsides and 

fences, in floodplain woodlands, marshes, and 

upland woods.

LOOK-ALIKES: While numerous unrelated species 

have similar alternate, compound leaves and grow 

to a similar size in the same habitat, most unrelated 

potential look-alikes differ by having samara or pod 

fruits and flowers that are either non-showy or not 

symmetrical like chinaberry tree. The related exotic 

but cultivated neem (Azadirachta indica) has white 

flowers, longer fruits.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: Chinaberry tree fruits are reportedly highly 

poisonous to humans and other mammals. 

Look-alike: neem (William M. 

Ciesla, Forest Health Management 

International, bugwood.org)
50 New Invaders of the Northeast and Northcentral United States PINKISH PURPLE FLOWERSJapanese maple

Acer palmatum Thunb.

SYNONYMS: palmate maple, Acer palmatum var. dissectum (Thunb.) Miq.

ORIGIN: Japan, Korea

GROWTH TRAITS: Small deciduous tree or large multi-stemmed shrub typically 

growing 10-25' (3-8 m) tall. Trees grow from a shallow root system, and its low 

branches form a broad, rounded canopy. There are hundreds of cultivars which 

vary dramatically in their size, shape, and the color/shape of leaves and bark. The 

bark of many cultivars is greenish-red on new growth but typically grayish-brown 

at maturity. Leaves are opposite and attached to the branch with long petioles. 

Leaves are 2-5" (5-13 cm) wide with 5 or 7 (sometimes 9) lobes, and are shaped 

like the palm of a hand. Each lobe is toothed and very pointed at the tips. Lobes of 

some cultivars are very finely divided. Leaf color varies from green to bright red to 

deep maroon, and leaves may turn yellow, bronze, and reddish-purple in autumn 

before falling to the ground. Flowers appear in clusters of 10-20 in spring as leaves 

open. Each flower is up to 0.25" (6 mm) across and has 5 purplish-red sepals and 

5 yellow-green to pale pink petals. The fruits are up to 2" (5 cm) wide, are double 

a b

Japanese maple a. tree with green foliage; b. shrub with red foliage (a. AnRo0002; b. John Ruter, 

University of Georgia, bugwood.org)
New Invaders of the Northeast and Northcentral United States 51

Family Sapindaceae

c d e f

Japanese maple c. green leaves; d. red, finely divided leaf; e. flowers; e. fruit (samara)(c. Kenpei; d. 

James Steakley; e. Sten Porse; f. © lopezeim, iNaturalist.org)

samaras with two winged seeds fused together, and vary from green to red. Plants 

may live up to 100 years, but typically less under cultivation. 

REPRODUCTION: Spreads by seed. The majority 

of seeds germinate within one year, though some 

may remain viable longer.

HABITAT: Capitalizes on disturbance or intentional 

planting to establish initially, but then readily 

spreads into undisturbed areas. It does well in 

moist soil and full sun in colder climates and 

partial shade in hot climates. It can be found at 

forest edges, along streams and roadsides, and in 

urban gardens.

LOOK-ALIKES: The opposite, palmately lobed leaves 

and samara fruits help differentiate this species from unrelated look-alikes. Within 

the family, many maples differ by having smoothly lobed leaves and fruits fused 

at different angles. The native silver maple (Acer saccharinum) has deeply divided 

leaves that may resemble some Japanese maple cultivars. It differs by having more 

rounded leaf lobes and tips and growing as a tree 50-80' (15-24 m) tall. 

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: Japanese maple is a popular ornamental 

with hundreds of cultivars available, and it is also 

frequently used in bonsai.

Look-alike: silver maple 

leaf (Paul Wray, Iowa State 

University, bugwood.org)
52 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Baby's breath

Gypsophila paniculata L.

SYNONYMS: common gypsophila, panicled baby's-breath

ORIGIN: Eurasia

GROWTH TRAITS: Herbaceous, perennial growing 1.3-3.3' (0.4-1 m) tall 

from a thick, deep taproot. Plants develop one shoot the first year and numerous 

branched stems in subsequent years. Stems are slender and swollen at nodes. 

Leaves are opposite, lance-shaped, narrow, and 0.8-3.5" (2-9 cm) by 0.08-0.4" 

(2-10 mm) wide. Leaves are light green and leathery with smooth margins and a 

distinct midvein on their undersides. Beginning in its third year, the plant flowers 

profusely throughout summer and into fall. Flowers are up to 0.3” (8 mm) in 

diameter and have 5 petals, long, narrow sepals, and long stamens. Flowers are 

typically white, though some may be light pinkish-purple. Fruits are spherical 

capsules that contain several black, rough, and bean-shaped seeds 0.04-0.08" 

(1-2 mm) long.

REPRODUCTION: Reproduces by seed. Seeds remain viable for 5-7 years.

a b

Baby's breath a. plant; b. infestation (a. © nmori; b. Stefan.lefnaer)
New Invaders of the Northeast and Northcentral United States 53

Family Caryophyllaceae

c d e

Baby's breath c. leaves and stem; d. flowers; e. seeds (c. Stefan.lefnaer; d. Joseph M. DiTomaso, 

University of California Davis, bugwood.org; e. John Alan Elson)

HABITAT: Grows best in full sun and coarse soil. In North America, it is typicaly 

found in flood plains, fields, roadsides, beaches and other open, disturbed sites.

LOOK-ALIKES: The combination of its bushy 

appearance and numerous tiny white flowers that 

each have 5 petals, long sepals, and long stamens 

help differentiate baby's breath from many 

potential look-alikes. Other species of Gypsophila

(all exotic) are present in North America and all 

resemble baby's breath to some extent. Showy 

baby's breath (G. elegans) differs with its annual or 

biennial life cycle and having more slender roots. 

Glandular baby's breath (G. scorzonerifolia) has 

glandular hairs covering its bracts and flower stalks. 

Creeping baby's breath (G. repens) is a mat-forming 

species that grows much shorter and has smaller 

leaves than baby's breath.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: This species is frequently grown as an 

ornamental and has escaped cultivation at many 

locations.

Look-alike: creeping baby's 

breath (© experiencealaska, 

iNaturalist.org)
54 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Broadleaved pepperweed

Lepidium latifolium L.

SYNONYMS: perennial pepperweed, broadleaf peppergrass, broadleaf pepperwort, 

dittander, peppergrass, perennial peppergrass, perennial pepperwort, tall whitetop

ORIGIN: Asia, Europe, the Mediterranean

GROWTH TRAITS: Herbaceous, perennial growing 1-5' (0.3-1.5 m) tall from 

an extensive creeping root system. Rosettes develop in late fall to early spring and 

have waxy, toothed leaves that are 4-12" (10-30 cm) long and 1-2" (2.5-5 cm) 

wide. Stems emerge from semi-woody crowns or the creeping roots. Stem leaves 

are waxy, alternate, oblong, and often have toothed margins. Stem leaves are up 

to 4" (10 cm) long and decrease in size higher up on the stem. Lower leaves have 

petioles while upper leaves do not. Flowers appear spring through summer in 

dense clusters at stem tips. Flowers are white, up to 0.1” (3 mm) in diameter, 

and have 4 petals and 6 stamens. Fruits are spherical to slightly oval, up to 0.8" 

(2 mm) long, contain 2 seeds, and are typically smooth but may be slightly hairy.

a b

Broadleaved pepperweed a. plant; b. infestation (a. Mary Ellen (Mel) Harte; b. Leslie J. Mehrhoff, 

University of Connecticut; a,b. bugwood.org)
New Invaders of the Northeast and Northcentral United States 55

Family Brassicaceae

c d e

Broadleaved pepperweed c. leaves and stem; d. flowers; e. matured and dried out fruits (c. Mary 

Ellen (Mel) Harte; d,e. Leslie J. Mehrhoff, University of Connecticut; c-e. bugwood.org)

REPRODUCTION: Reproduces occasionally by seed, but most spread is 

vegetative by sending new shoots up from its creeping root system (or fragments) 

and its semi-woody crown. Seeds may remain viable for at least two years.

HABITAT: Tolerates a wide variety of conditions. 

It is a frequent invader of moist sites such as 

riparian areas and wetlands, but readily spreads 

into other habitats, including arid rangelands, open 

mountainsides, roadsides, and other disturbed sites. 

LOOK-ALIKES: Several related species are present 

in North America and resemble broadleaved 

pepperweed with their similar leaves and/or tiny 

flowers with 4 petals and 6 stamens. Many lookalikes have yellow flowers and linear fruit. Of those 

with white flowers, several look alikes have different 

leaf and fruit shape and grow smaller than broadleaved pepperweed. The exotic 

whitetop (Lepidium draba) can look very similar, but typically only grows 16-

20" (40-50 cm) tall and has heart-shaped fruit. The native but weedy common 

pepperweed (L. densiflorum) has longer inflorescences and flattened fruits.

NOXIOUS WEED LISTINGS: CT, MA, NH, NY, WI (all Prohibited)

NOTES: This species alters the ecosystem in which 

it grows by changing the concentration of different 

chemical constituents throughout the soil profile, 

affecting both the type and number of species 

capable of growing there.

Look-alike: whitetop (Luis 

Fernández García)
56 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Burnet-saxifrage

Pimpinella saxifraga L.

SYNONYMS: solidstem burnet saxifrage, pimpinella, scarlet pimpernel

ORIGIN: temperate Asia, temperate Europe

GROWTH TRAITS: Herbaceous, erect perennial typically growing 1-3' (0.3-

0.9 m) tall from a large, strongly scented taproot. Stems are slender, solid (not 

hollow), faintly ribbed, and covered in very short hairs. Leaves are alternate 

and divided into multiple leaflets. Basal leaves are 3-12" (7.5-30 cm) long with 

coarsely toothed lobes. Leaves get progressively smaller up the stem and leaflets 

become increasingly narrow. Flowers appear throughout summer. The umbel 

inflorescence (all flower stalks arising from the same point) is compound; there 

are 7-20 groups (umbellets), each containing 10-20 flowers. Each tiny flower is 

0.16" (4 mm) across and has 5 white petals. Fruits are slightly ribbed, oval pods 

up to 0.12" (3 mm) long that each contain 2 seeds flattened, ovate seeds. 

REPRODUCTION: Spreads by seed. The majority of seeds germinate within 

the first year.

a b

Burnet-saxifrage a. plant; b. infestation (a. © alderash, iNaturalist.org; b. Jeffrey Flory, bugwood.org)
New Invaders of the Northeast and Northcentral United States 57

Family Apiaceae

c d e f

Burnet saxifrage c. basal leaves; d. stem leaf and stem; e. inflorescence; f. fruits (c-e. Jeffrey Flory, 

bugwood.org; f. Andreas Rockstein)

HABITAT: Grows best in full sun and does well in chalky, disturbed soils. It can 

be found in moist to dry soils of meadows, grasslands, and open woodlands.

LOOK-ALIKES: The white umbel inflorescences, 

5-petal flowers, and odorous taproot of burnetsaxifrage differentiate it from unrelated look-alikes. 

Numerous relatives in the Apiaceae are present 

in North America and many resemble burnetsaxifrage. The native wild carrot (Daucus carota) 

has a similar white umbel inflorescence, divided 

leaves, short stem hairs, and odorous root. Wild 

carrot differs by being a biennial and in having 

numerous divided and lobed bracts beneath its 

inflorescence and more finely divided leaves. The 

seedlings and basal leaves of wild parsnip (Pastinaca 

sativa) closely resemble those of burnet-saxifrage, 

however wild parsnip grows much taller and denser and produces yellow flowers 

on its umbels. 

NOXIOUS WEED LISTINGS: WI (Restricted)

NOTES: In Great Britain, this species was intentionally 

cultivated on chalky soils as nutritious fodder for 

sheep and cattle. It is occasionally sold in North 

America as an ornamental or in homeopathy. 

Because it closely resembles many toxic species, 

extreme caution should be used when collecting this species for homeopathic 

uses.

Look-alike: wild carrot 

(Tigerente)
58 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Goatsrue

Galega officinalis L.

SYNONYMS: professor weed

ORIGIN: Europe, the Mediterranean

GROWTH TRAITS: Herbaceous perennial that grows up to 6’ tall (1.8 m) from 

a deep taproot. Plants are often bushy and multi-stemmed. Stems are somewhat 

hollow and cylindrical. Leaves are alternate and compound, divided into 6-10 

pairs of leaflets and a single terminal leaflet. Flowers occur in clusters at stem 

tips or leaf axils from June to July. Flowers are white to light purple and pealike (having a banner, wing and keel, typical of the pea family). Fruits are small, 

narrow, bean-like pods just over 1” long (3 cm) that contain up to 9 seeds each.

REPRODUCTION: Reproduces by seed. Seeds may remain viable in the soil 

for up to 10 years.

HABITAT: Grows best in full sun and moist soil. In North America, it can be 

a b

Goatsrue a. plant; b. infestation (a. Sasha Shaw, King County NCWB; b. Carl Bullock)
New Invaders of the Northeast and Northcentral United States 59

Family Fabaceae

c d e

Goatsrue c. leaves and leaflets; d. flowers and flower buds; e. seed pods (c,e. Sasha Shaw, King 

County NWCB; d. H. Zell)

found in or along cropland, ditchbanks, irrigation waterways, uncut pastures, 

fence lines, roadways and wet, marshy areas, capitalizing on disturbance.

LOOK-ALIKES: The unique, pea-like flowers 

in combination with the compound leaves help 

differentiate this species from all other plants 

outside of the Fabaceae. Within the family, a 

number of milkvetch (Astragalus) and vetch (Vicia) 

species resemble goatsrue. Milkvetch leaves also 

have one terminal leaflet, but they tend to have 

more leaflet pairs (10-16). Vetches are more vining 

in habit, and have clasping tendrils in place of the 

terminal leaflet.

NOXIOUS WEED LISTINGS: MA (Prohibited), 

PA, RI, VT, WV (all Noxious) 

NOTES: This species was initially introduced to 

North America as a potential forage plant; however, 

the leaves and stems contain a poisonous alkaloid 

that makes the plant unpalatable to livestock and 

is toxic in large quantities.

Look-alike: bush vetch (Erlend 

Bjørtvedt)
60 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Italian arum

Arum italicum Mill.

SYNONYMS: Italian lords-and-ladies, orange candleflower, cuckoo’s pint

ORIGIN: Eurasia, Mediterranean

GROWTH TRAITS: Herbaceous, stemless perennial growing 1-1.5’ (30-45 cm) 

tall from a tuberous root system. Main tubers produce a number of daughter 

tubers that are attached during the growing season, but separate from the main 

tubers over time, forming separate plants. In mild climates, new leaves appear 

in autumn; in cold climates, leaves die back for winter and new leaves appear in 

spring. Leaves are typically 3.5-8” (9-20 cm) long and have long petioles (6-14” 

or 15-35 cm). Leaves are oval to arrowhead-shaped, have smooth margins, and 

may be solid green or variegated with veins colored silver-gray to yellow-green. 

Tiny white flowers are produced in spring on a long, narrow spadix surrounded 

by a large greenish-white spathe. The leaves and spathe die back after flowering, 

leaving only the spadix, which produces tight clusters of green berries that turn 

orange-red with maturity. 

a b

Italian arum a. plant; b. infestation (a. Consultaplantas; b. Wendy DesCamp, Washington State 

Noxious Weed Control Board)
New Invaders of the Northeast and Northcentral United States 61

Family Araceae

c d e f

Italian arum c. variegated leaves; d. spadix and spathe; e. cutaway of spadix and spathe; f. fruit (c. © 

Anne Parsons, iNaturalist.org; d. Orchi; e. Pancrat; f. Dominicus Johannes Bergsma)

REPRODUCTION: Spreads by seed and vegetatively via daughter tubers. Seeds 

are reportedly only viable for a short time.

HABITAT: Prefers moist and partially shaded 

habitats, but also grows well in full sun. It is found 

in open woodlands, forest edges and understories, 

riparian areas, old gardens, and disturbed locations 

near urban development.

LOOK-ALIKES: Though the leaves of Italian arum 

may resemble unrelated species, the spadix/spathe 

inflorescence distinguishes this species from all 

potential look-alikes outside the Araceae. Within 

the family, the white flowers, arrow-head leaves, 

and terrestrial habitat largely help differentiate 

Italian arum. The similar green arrow arum (Peltandra virginica) and water arum 

(Calla palustris) occur in bogs and marshes. The native green dragon (Arisaema 

dracontium) and Jack-in-the-pulpit (Arisaema triphyllum) have similar fruit. 

Green dragon has only one leaf which is divided into 5-13 long, elliptical leaflets. 

Jack-in-the-pulpit typically has two leaves, each divided into 3 leaflets, and its 

spathe is typically green or purple on the outside and dark purple with greenishwhite stripes insde (coloration varies). 

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state. 

NOTES: All parts of the plant are poisonous and 

irritating to the skin.

Look-alike: water arum (Anneli 

Salo)
62 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Queen of the meadow

Filipendula ulmaria (L.) Maxim.

SYNONYMS: meadowsweet, European meadowsweet, mead wort, double lady 

of the meadow, Spiraea ulmaria L., Thecanisia ulmaria (L.) Raf.

ORIGIN: temperate Asia

GROWTH TRAITS: Upright, herbaceous perennial typically growing 3-5' 

(0.9-1.5 m) tall and half as wide from a rhizomatous root system. Stems are 

rigid and often tinged in red. Leaves are alternate and divided into 3-5 pairs of 

opposite leaflets with one terminal leaflet. Terminal leaflets are deeply lobed into 

3 segments, each segment resembling a side leaflet. Side leaflets are ovate with a 

pointed tip and have distinct venation and doubly-toothed margins. Side leaflets 

are up to 3" (7.5 cm) long with lighter-colored and hairy undersides. At the base 

of the leaf stalk is a pair of leafy appendages that appear to clasp the stem. Very 

fragrant flowers bloom in early to mid summer. The tiny flowers are up to 0.3" 

(08 mm) in diameter, have 5 white petals, numerous long stamens, and appear 

in large clusters at stem tips or upper leaf axils. The fruits are intertwined, twisted 

achenes up to 0.25" (6 mm) long that are green initially, but mature to brown. 

a b

Queen of the meadow a. plant; b. infestation (a. Christian Fischer; b. Alethe)
New Invaders of the Northeast and Northcentral United States 63

Family Rosaceae

c d e

Queen of the meadow c. leaf with leaflets; d. flowers; e. fruit (c. Erlend Bjørtvedt; d. © Almantas 

Kulbis, iNaturalist.org; e. GFDL)

REPRODUCTION: Spreads by seed and rhizomes. Seed longevity is unknown. 

HABITAT: Prefers damp or wet sites where the water levels fluctuate but where 

the soil is not continuously water-logged. In North America, this includes 

streams and irrigation ditches, moist meadows, roadsides where water gathers, 

and wetlands.

LOOK-ALIKES: Several unrelated species resemble 

queen of the meadow with their compound, 

toothed leaves and large clusters of tiny, white, 

5-petal flowers, such as the native American 

elderberry (Sambucus nigra ssp. canadensis). 

American elderberry differs by growing as a shrub 

or small tree and having black berry-like fruits. 

Several related species of Spiraea also closely 

resemble queen of the meadow, however species in 

that genus grow as shrubs. The more closely related 

dropwort (Filipendula vulgaris) and queen of the 

prairie (F. rubra) have a similar overall shape, but 

neither has twisted fruits. The leaves of dropwort are more divided as to appear 

fern-like, and the flowers of queen of the prairie are pink.

NOXIOUS WEED LISTINGS: WI (Restricted)

NOTES: This species has long been utilized in 

herbal remedies for its medicinal properties and 

as an ornamental for its sweet-smelling flowers. It 

frequently escapes cultivation in North America.

Look-alike: dropwort (Magnus 

Manske)
64 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Tara vine

Actinidia arguta (Siebold & Zucc.) Planch. ex Miq.

SYNONYMS: hardy kiwi

ORIGIN: Asia

GROWTH TRAITS: Perennial, deciduous, twining vine with many stems 

growing from a fleshy root system. Vines are greenish when young, but at 

maturity become woody and grayish-brown with distinct lenticels. Vines grow 

vigorously, typically reaching 15-25' (4.6-7.6 m) long by 8' (2.4 m), and can 

form a creeping groundcover or twine around adjacent vegetation and structures. 

Leaves are alternate, have long red petioles, are green, and often remain green 

late into fall. Leaves are 3-5" (7.5-12.7 cm) long and broadly lance-shaped with 

pointed tips and toothed margins. Flowers appear in small clusters from leaf 

axils in summer. Male and female flowers are produced on separate plants. Both 

have 4-6 whitish-green petals with numerous dark-tipped stamens and are 0.4-

0.8" (1-2 cm) across. Female flowers have a raised center with white, radiating 

filaments. Fruits are oblong, fragrant, greenish-pink berries up to 1.2" (3 cm) 

a b

Tara vine a. vine; b. infestation (a. © Wendy Cutler; b. Sten Porse)
New Invaders of the Northeast and Northcentral United States 65

Family Actinidiaceae

c d e f

Tara vine c. leaves; d. female flower; e. fruit; f. fruit cross-section (c. Appaloosa, bugwood.org; d,e. 

© Melanie J Watts; f. © harum.koh, iNaturalist.org)

long that contain green, fleshy pulp and tiny brown seeds. In cold climates, 

plants die back in the fall and re-sprout from the root system in spring. 

REPRODUCTION: Spreads by seed. Seed longevity 

is unknown.

HABITAT: Tolerates full sun as well as shady, 

moist sites with cold winters. New growth may 

be frost sensitive. Grows best in moist but welldrained soil and readily escapes gardens to invade 

forest understories and margins, streamsides, and 

meadows.

LOOK-ALIKES: The regularly cultivated commercial 

kiwifruit (Actinidia chinensis) has leaves with blunt 

tips and fruits that are up to 2.5" (6.3 cm) long and 

covered in brown fuzz. The exotic Oriental bittersweet (Celastrus orbiculatus) and 

native American bittersweet (C. scandens) are similar vines with large, toothed, 

alternate leaves and small white flowers; they differ by producing bright reddish 

orange-berry fruits.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state. 

NOTES: This species is a popular ornamental. Its fruit 

are sweeter than commercial kiwifruit (A. chinensis), 

and it is much more cold tolerant. More recently it 

is escaping gardens and becoming invasive. 

Look-alike: kiwifruit 

(Lazaregagnidze)
66 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Deutzia

Deutzia scabra Thunb.

SYNONYMS: fuzzy pride-of-Rochester, fuzzy deutzia

ORIGIN: Japan

GROWTH TRAITS: Deciduous, multi-stemmed, rounded shrub growing 6-10' 

(1.8-3 m) tall by 6-8' (1.8-2.4 m) wide from a suckering root system. Stems are 

upright initially, but arch and become leggy with age. The orangish-brown bark 

of older stems is exfoliating, sloughing off to reveal lighter brown bark beneath. 

Leaves are medium to dark green, opposite, 2-4" (5-10 cm) long by up to 2" (5 

cm) wide, and elliptical with a pointed tip. Leaves have slightly toothed margins 

and are rough-textured and slightly hairy on both sides. Flowers bloom profusely 

in late spring/early summer in large clusters 3-6" (7.5-15 cm) long from leaf axils 

and stem tips. Flowers are fragrant, star-shaped, and up to 0.8" (2 cm) in diameter. 

The most common cultivar has "double flowers" which appear as a mass of white 

petals that may be tinged with pale pink on their undersides. Escaped individuals 

often revert back to a more wild form without the doubled flower. Fruits are round 

capsules up to 0.2" (0.5 cm) wide that turn from green to brown with maturity and 

open to release numerous small seeds. Fruits often remain on stems through winter. 

a b

Deutzia a. plant; b. bark (a. Wouter Hagens; b. © Steven J. Baskauf, bioimages.vanderbilt.edu/)
New Invaders of the Northeast and Northcentral United States 67

Family Hydrangeaceae

c d e

Deutzia c. leaves; d. flowers; e. fruits and 3-parted leaf (c. Krzysztof Golik; d,e. Wouter Hagens)

REPRODUCTION: Spreads by seed and suckering from its root system. Seeds 

may remain viable for at least three years. 

HABITAT: Grows best in moist, well-drained soils in full sun, but can tolerate 

shade and drought once established. It is a frequent escapee from gardens and 

readily invades open, disturbed areas.

LOOK-ALIKES: The shrubby growth and opposite, 

elliptical leaves resemble many species of exotic 

bush honeysuckles (Lonicera spp.), including Amur 

honeysuckle (L. maackii). These species are easily 

differentiated during flowering and fruiting, however, 

as bush honeysuckle flowers are asymmetrical with 

(generally) two lips and are tubular at their base. 

Bush honeysuckles also produce berry fruit. The 

exotic sweet mock orange (Philadelphus coronarius) 

has very similar shape, bark, leaves, and fruit. Sweet 

mock orange flowers are larger in diameter (up to 

1.5" or 4 cm) and have 4 large white petals with 

numerous yellow stamens. The related exotic 

ornamental slender deutzia (Deutzia gracilis) grows 

shorter, has narrower and smooth leaves, and its 

flowers have 5 petals and numerous yellow stamens.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeaster/northcentral state.

NOTES: This species is a popular ornamental for gardens in temperate regions 

and easily escapes cultivation. Escapees frequently lose the "double flowers".

Look-alike: Amur honeysuckle 

(Daderot)
68 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Japanese pachysandra

Pachysandra terminalis Siebold & Zucc.

SYNONYMS: carpet-box, Japanese spurge

ORIGIN: temperate Asia

GROWTH TRAITS: Evergreen shrub growing 4-10" (5-25 cm) tall from a 

stoloniferous root system. Underground and aboveground runners root at 

nodes and send up stems, eventually forming dense mats. Leaves are sometimes 

alternate but are frequently whorled at branch tips and are ovate to elliptical 

to obovate and coarsely toothed at their tips. Most leaves are 2-4" (5-10 cm)

long, waxy, and a rich dark, glossy green, but some cultivars are variegated white 

and green. Foliage typically remains green throughout winter. Flowers appear 

in erect clusters 1-2" (2.5-5 cm) long at branch tips in early spring. Flowers are 

0.5" (1.3 cm) long with white, bristle-like petals and maroon-tipped stamens. 

Fruits are white, berry-like, and 0.5" (1.3 cm) long, but are rarely produced in 

North America.

REPRODUCTION: Spreads primarily via stolons.

a b

Japanese pachysandra a. plant; b. infestation (a,b. Karan A. Rawlins, bugwood.org)
New Invaders of the Northeast and Northcentral United States 69

Family Buxaceae

c d e

Japanese pachysandra c. solid green leaves; d. variegated leaves; e. flowers (c. Karan A. Rawlins, 

University of Georgia, bugwood.org; d. Krzysztof Ziarnek, Kenraiz; e. Algirdas)

HABITAT: Grows in a variety of soils but does best in well-drained soils rich 

in organic matter and in partial to full shade. It can be found invading forest 

understories, often spreading from locations where it was intentionally planted.

LOOK-ALIKES: Several native and exotic 

understory groundcover species are present in 

North America and resemble Japanese pachysandra 

with their evergreen, waxy leaves and short height. 

The combination of whorled, obovate leaves 

toothed at their tips, clusters of small, bristlylooking white flowers, and typical lack of fruit help 

differentiate this species from most potential lookalikes. The native Allegheny spurge (Pachysandra 

procumbens) has similar bristly-looking flowers 

and leaves toothed at their tips. Allegheny spurge 

differs by having leaves being either deciduous or 

more tattered over winter, longer flower clusters, and flowers that are pale pink 

instead of creamy white.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: Japanese pachysandra is a popular 

ornamental groundcover, frequently used in 

garden understories because of its shade tolerance 

and evergreen foliage. However, its rhizomatous 

roots allow it to spread rapidly into natural settings.

Look-alike: Allegheny spurge 

(Salicyna)
70 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Privets 

Ligustrum spp.

a

b

c

California privet a. plant; b. leaves; c. inflorescence (a. Georges Jansoone; b. Robert Vidéki, Doronicum 

Kft., bugwood.org; c. Leslie J. Mehrhoff, University of Connecticut, bugwood.org)

d

e

f

Chinese privet d. plant; e. leaves; f. inflorescence (d. Chris Evans, University of Illinois; e. Karan A. 

Rawlins, University of Georgia; f. Bidgee)(d,e. bugwood.org)
New Invaders of the Northeast and Northcentral United States 71

Family Oleaceae

g

h

i

Glossy privet g. plant; h. leaves; i. inflorescence (g,h. Karan A. Rawlins, University of Georgia, 

bugwood.org; i. Krzysztof Ziarnek, Kenraiz)

j

k

l

Japanese privet j. plant; k. leaves; l. inflorescence (j. John Ruter, University of Georgia; k. James H. 

Miller, USDA Forest Service; l. Karan A. Rawlins, University of Georgia; j-l. bugwood.org)
72 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Privets (continued)

Ligustrum spp.

NAMES: California privet (CalP): Ligustrum ovalifolium Hassk.

 Chinese privet (ChiP): Ligustrum sinense Lour.

 Glossy privet (GP): Ligustrum lucidum W.T. Aiton 

 Japanese privet (JP): Ligustrum japonicum Thunb.

SYNONYMS: CalP: Korean privet, garden privet, oval-leaved privet; ChiP: 

small-leaf privet, L. microcarpum Kaneh. & Sasaki; GP: tree privet, broadleaf 

privet, giant privet, large-leaf privet; JP: wax leaf privet

ORIGIN: CalP and JP: Japan, Korea; ChiP: China, Laos, Taiwan, Vietnam; GP: 

China

Trait California

L. ovalifolium

Chinese

L. sinense

Glossy

L. lucidum

Japanese

L. japonicum

Typical

Height

8-15' 

(2.4-4.6 m) 

10-18' 

(3-5.5 m)

Up to 33' 

(10 m)

8-12' 

(2.4-3.7 m)

Leaves

1.2-2.4” (3-6 cm) 

long; elliptical with 

rounded tips; veins 

distinct

1.2-2" (3-5 cm) 

long; elliptical with 

tips more rounded 

than base; veins 

distinct; underside 

of midrib hairy

3-4.7" (8-12 cm) 

long; ovate with 

tips more pointed 

than base; veins 

distinct

2-3” (5-8 cm) 

long; ovate with 

tips more pointed 

than base; veins 

indistinct

Flowers

Flower tube 2-3x 

longer than free 

petals; stamens 

don't extend 

beyond petals; 

strong odor

Flower tube 

typically shorter 

than free petals; 

stamens extend 

beyond petals; 

strong odor

Flower tube 

typically shorter 

than free petals; 

stamens don't 

extend beyond 

petals

Flower tube nearly 

as long as free 

petals; stamens 

extend beyond 

petals

Fruit

0.25" (6 mm) dia.; 

nearly spherical; 

purple-black

Less than 0.25" (6 

mm) long; slightly 

oval; blue-black

0.4" (10 mm) 

long; oblong; blueblack

0.25" (6 mm) 

long; slightly oval; 

purple-black

GROWTH TRAITS: All four species are shrubs or small trees with single or 

multiple stems and long, leafy branches that grow from a shallow, suckering root 

system. Stem bark is smooth, pale brown to gray, and has lighter-colored lenticels. 

Leaves are opposite, leathery, dark glossy green above and lighter green below, 

and have smooth margins. All four species are evergreen in warm climates, but 

leaves become semi- or fully deciduous in areas with cold winters. Flowers appear 

in clusters from late spring through early summer. Flowers are small and creamy 

white with 4 recurved petals that are fused and tubular at their base. Berry-like 

fruits mature a purple-black or blue-black in fall and persist into winter.
New Invaders of the Northeast and Northcentral United States 73

Family Oleaceae

California privet (CalP): Typically grows as a multistemmed shrub 8-15' (2.4-4.6 m) tall, though some 

may grow taller as small trees. Most leaves are 1.2-

2.4" (3-6 cm) long with petioles up to 0.25" (6 mm) 

long and are yellowish-green on their undersides. 

They are elliptical, have slightly rounded tips, and 

have obvious midribs with distinct side veins. Flowers 

appear in clusters at branch tips. The flower tube is 2-3x longer than the free 

petals, and the stamens typically don't extend beyond the petals. Flowers have a 

strong odor. Fruits are nearly spherical, 0.25" (6 mm) across, and purple-black.

Chinese privet (ChiP): Typically grows as a multistemmed shrub 10-18' (3-5.5 m) tall, though some 

may grow taller as small trees. Branchlets are round 

and often hairy. Most leaves are 1.2-2" (3-5 cm) long 

with petioles up to 0.3" (8 mm) long. Leaves are 

elliptical with tips more rounded than their base. Leaf 

tips are often slightly indented. Leaves have obvious 

midribs with distinct side veins, and the underside of the midrib is hairy. Flowers 

appear in clusters at the tips of terminal and axillary branches. The flower tube 

is typically shorter than the free petals, and the stamens typically don't extend 

beyond the petals. Flowers have a strong odor. Fruits are slightly oval-shaped, 

less than 0.25" (6 mm) long, and blue-black at maturity.

Glossy privet (GP): Grows as a multi-stemmed shrub 

or (more typically) a single-stemmed tree up 33' (10 

m) tall. Most leaves are 3-4.7" (8-12 cm) long with 

petioles 0.4-0.8" (1-2 cm) long. They are ovate, have 

tips more pointed than the base, and have obvious 

midribs and distinct side veins. Many glossy privet 

leaves appear to fold slightly inward toward to the 

midvein. Flowers appear in clusters at branch tips. The flower tube is typically 

shorter than the free petals, and the stamens typically don't extend beyond 

the petals. Fruits are oblong, less than 0.4" (10 mm) long, and blue-black at 

maturity.

Japanese privet (JP): Typically grows as a multi-stemmed shrub 8-12' (2.4-3.7 

m) tall, though some may grow taller as small trees. Most leaves are 2-3" (5-8 

cm) long with petioles up to 0.5" (1.2 cm) long. They are ovate to elliptical, 

have tips slightly more pointed than the base, and have obvious midribs and 

California privet

Chinese privet

Glossy privet
74 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Privets (continued)

Ligustrum spp.

Japanese privet

indistinct side veins. Leaf margins frequently curl 

under slightly. Flowers appear in clusters at branch 

tips. The flower tube is nearly as long as the free 

petals, and the stamens extend beyond the petals. 

Fruits are oval-shaped, less than 0.25" (6 mm) long, 

and purple-black at maturity.

REPRODUCTION: All four species spread by seed and suckering from the root 

system. The seeds of all four species are typically only viable for one year. 

HABITAT: All four species tolerate a wide range of soil conditions and can grow 

in full sun to heavy shade. All grow best in mesic soil in full to partial sun and 

are typically found at forest edges or in floodplains, fields, and disturbed forests.

LOOK-ALIKES: Several additional privet species have been introduced to North 

America and are difficult to differentiate. They vary slightly in leaf size, fruit 

shape and size, petal length, stamen length, and the presence/absence of hairs 

on stems. Perhaps the most frequently encountered in the northeastern and 

northcentral USA include European privet (L. vulgare) and border privet (L. 

obtusifolium). European privet is a multi-branched shrub, typically 10-15' (3-

4.5 m) tall and wide with lance-shaped leaves up to 2.5" (6 cm) long. Leaves are 

typically glossy and have obvious midribs with indistinct side veins. European 

privet flower tubes are about as long as the free petals, and the stamens extend 

beyond the petals only slightly. Flowers have a strong odor. European privet fruits 

are spherical, just over 0.25" (6 mm) in diameter, and glossy black at maturity. 

Border privet is an arching, multi-branched shrub typically growing 10-12' (3-

3.7 m) tall and up to 15' (4.5 m) wide. Branchlets are round and often hairy. 

Most leaves are up to 2.5" (6 cm) long, elliptical with either rounded or pointed 

tips, and have obvious midribs with less distinct side veins. The underside of the 

midrib is hairy. Border privet flowers are often hairy and also have a strong odor. 

Flower tubes are 2-3x longer than the free petals, and the stamens typically don't 

extend beyond the petals. Fruits are oval-shaped, 0.25" (6 mm) long, and a waxy 

bluish-black at maturity.

NOXIOUS WEED LISTINGS: None of these four species are listed as noxious 

in any northeastern/northcentral state.

NOTES: Privets were introduced to North America in the 1800s. They are often 

planted as ornamentals and in hedgerows and regularly escape cultivation.
New Invaders of the Northeast and Northcentral United States 75

Family Oleaceae
76 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Viburnums 

Viburnum spp.

Trait

Doublefile

V. plicatum var. 

tomentosum

Linden

V. dilatatum

Siebold's

V. sieboldii

Typical

Height

8-10' 

(2.4-3 m) 

8-10' 

(2.4-3 m) 

15-20' 

(4.6-6.1 m)

Bark

Smooth, gray-brown, 

prominent orange 

lenticels

Smooth, gray-brown, 

prominent orange 

lenticels

Rough, furrowed, 

prominent lenticels

Leaves

2-4" (5-10 cm) long; 

elliptical or ovate; hairy 

on undersides and petiole; 

burgundy in fall

2-5" (5-12.5 cm) long; 

variable shape; covered 

in soft hairs; bronze or 

burgundy in fall

2-5" (5-12.5 cm) long; 

elliptical or ovate; hairy 

on veins and petiole; no 

fall color; foul odor when 

crushed

Flowers

Flat-topped cluster in 

doublefile form along 

branches; outer flowers 

sterile, showy; inner flowers 

fertile, tiny, non-showy

Flat-topped cluster at 

branch tips; each flower 

0.25" (6 mm) in diameter 

Flat-topped cluster at 

branch tips; each flower 

0.25" (6 mm) in diameter 

Fruit 0.5" (13 mm) long; 

oblong; black at maturity

0.3" (8 mm) long; slightly 

oblong; red at maturity

0.3-0.5" (8-13 mm) long; 

spherical to oblong; black 

at maturity

a

b

c

Doublefile viburnum a. plant; b. leaves and inflorescence; c. several immature (red) and one mature fruit 

(black) (a. W.Baumgartner; b. Wouter Hagens; c. © Phil Bendle, Friends of Te Henui, T.E.R:R.A.I.N)
New Invaders of the Northeast and Northcentral United States 77

Family Adoxaceae

d

e

f

Linden viburnum d. plant; e. ovate, lobed leaves and inflorescence; f. rounded leaves and mature 

fruit (d. James Steakley; e. bastus917; f. Kenpei)

g

h

i

Siebold's arrowwood g. plant; h. leaves and inflorescence; i. immature (red) and mature fruit (black) (g. 

© Richard Howard, Smithsonian Institution; h. Qwert1234; i. © Margaret Roach, awaytogarden.com)
78 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Viburnums (continued)

Viburnum spp.

NAMES: Doublefile viburnum (DV): Viburnum plicatum Thunb. var. tomentosum Miq. 

 Linden viburnum (LV): Viburnum dilatatum Thunb.

 Siebold's arrowwood (SA): Viburnum sieboldii Miq.

SYNONYMS: DV: doublefile viburnum, Viburnum plicatum Thunb.; LV: linden 

arrowwood; SA: Siebold viburnum

ORIGIN: DV: China, Japan, Korea, Taiwan; LV: China, Japan, Korea; SA: Japan

GROWTH TRAITS: All three species are shrubs or small trees with multiple 

leafy stems that grow from a shallow root system. Leaves are opposite with 

prominent veins, coarsely toothed margins, and wrinkled surfaces. Flowers 

appear in clusters from May-June. Flowers are creamy white, star-shaped, and 

typically have 5 petals. Berry-like fruits mature in fall and persist into winter.

Doublefile viburnum (DV): There are multiple forms and varieties of Viburnum 

plicatum. This description and the corresponding images and distribution 

map pertain to one form with fertile florets, frequently referred to as  V. 

plicatum var. tomentosum or doublefile viburnum. This plant typically grows as 

a multi-stemmed shrub 8-10' (2.4-3 m) tall and is wider than tall, though some 

individuals may grow to 15' (4.6 m) in height. Branches extend horizontally, 

giving the plant a layered appearance. Young stems may be covered in soft hairs. 

The bark is mostly smooth and gray-brown with distinct orange lenticels. Leaves 

are elliptical to ovate, 2-4" (5-10 cm) long, and hairy on the undersides and the 

petiole. They are green in summer, turning burgundy in the fall. Flowers appear 

in flattened clusters in 'doublefile form' along branches. Each cluster contains an 

outer ring of large, showy, sterile florets surrounding a mass of tiny, non-showy 

fertile florets. Fruits are oval-shaped, 0.5" (13 mm) long, and green initially but 

turn red and then black at maturity. 

Linden viburnum (LV): Typically grows as a multi-stemmed shrub 8-10' (2.4-3 

m) tall. The bark is mostly smooth and gray-brown with distinct orange lenticels. 

Stems and leaves are often covered in soft hairs. Leaf shape is variable, ranging 

from nearly round to elliptical to lobed. Leaves are 2-5" (5-12.5 cm) long and 

are green in summer, turning bronze or burgundy in the fall. Flowers appear in 

flattened clusters at branch tips. Each flower is 0.25" (6 mm) in diameter. Fruits 

are slightly oval-shaped, 0.3" (8 mm) long, and green initially but red at maturity. 

Siebold's arrowwood (SA): Grows as a multi-stemmed shrub or small tree 

15-20' (4.6-6.1 m) tall. The bark is gray-brown, rough, and furrowed with 
New Invaders of the Northeast and Northcentral United States 79

Family Adoxaceae

prominent lenticels. Leaves are elliptical to oval-shaped and may have blunt 

tips. Leaves are 2-5" (5-12.5 cm) long, often leathery, and hairy on the veins and 

the petiole. They are deep green in summer and typically do not have a fall color. 

Crushed leaves often emit a foul odor, though some describe this as the smell of 

green peppers. Flowers appear in flattened clusters at branch tips. Each flower 

is 0.25" (6 mm) in diameter. Fruits are spherical to oval-shaped, 0.3-0.5" (8-13 

mm) long, and green initially but turn red and then black at maturity.

REPRODUCTION: All three species spread by seed but can also re-sprout from 

the root system following damage. Seeds of many viburnums remain viable for 

up to 10 years.

HABITAT: All three species tolerate a wide range of soil conditions and can grow 

in full sun to partial shade. All grow best in mesic soil in full to partial sun and 

are typically found at forest edges, fields, and disturbed forests.

LOOK-ALIKES: Several additional viburnum species are native to or have been 

introduced to North America, and many are difficult to differentiate. They vary 

slightly in leaf shape, fruit color, buds, and flower and fruit structure. 

NOXIOUS WEED LISTINGS: None of these species are listed as noxious in 

any northeastern/northcentral state.

NOTES: These exotic viburnums were intentionally introduced to North America 

in the 1800s. They are often planted as ornamentals and in hedgerows and 

regularly escape.

doublefile viburnum linden viburnum Siebold's arrowwood
80 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Castor aralia

Kalopanax septemlobus (Thunb.) Koidz.

SYNONYMS: prickly castor-oil tree, tree aralia

ORIGIN: Asia

GROWTH TRAITS: Deciduous tree typically growing 40-60' (12.2-18.3 m) tall, 

though individuals can grow much taller in their native range. Trees grow from 

a shallow, fleshy root system that may occasionally send up root sprouts. There 

is often one main trunk that branches to form an upright, oval canopy. Young 

bark is armed with long, thick spines; mature bark is generally spine-less, grayishbrown, and deeply furrowed. Leaves are 7-12" (18-30 cm) across, alternate, and 

attached to the branch with long petioles. Leaves, typically with 5-7 lobes, are 

shaped like the palm of a hand. Lobes may be shallow, or deeply divided nearly 

to the leaf base. Lobe margins are finely toothed. Leaves are dark glossy green 

initially, turning dull yellow to red in fall, but are not particularly showy. Flowers 

appear profusely in large clusters of umbels at stem branches in late summer. 

Each flower is tiny with 4-5 creamy white petals. The tiny, berry-like fruits occur 

in ball-like clusters and are black at maturity. Trees generally live over 40 years.

a b

Castor aralia a. tree; b. bark (a,b. T. Davis Sydnor, Ohio State University, bugwood.org)
New Invaders of the Northeast and Northcentral United States 81

Family Araliaceae

c d e f

Castor aralia c. spiny young stem; d. leaf; e. inflorescences; f. immature fruit (c. Andrew Gentry, 

bugwood.org; d. Krzysztof Ziarnek, Kenraiz; e. Dalgial; f. Magnus Manske)

REPRODUCTION: Spreads by seed and sprouting from the root system. Though 

the seeds are considered short-lived, some remain viable for at least two years.

HABITAT: Tolerates partial shade to full sun and 

grows best in deep, moist, fertile, well-drained soil. 

Castor aralia prefers cool, moist climates and is very 

cold tolerant. It can be found escaping landscaping 

and invading field and forest margins.

LOOK-ALIKES: The combination of tree habit, 

grayish furrowed bark, lobed leaves resembling the 

palm of a hand, and ball-like fruiting structures 

help differentiate castor aralia from most potential 

look-alikes. The native sweetgum (Liquidambar 

styraciflua) has similar bark, toothed leaves with 5 

palm-like lobes, and a ball-like fruiting structure. It differs from castor aralia by 

having thorn-less young bark, dense clusters of very non-showy green flowers, and 

fruits that become woody at maturity rather than consisting of numerous black, 

berry-like fruits. The native devil's walking stick (Aralia spinosa) resembles young 

castor aralia with its somewhat similar flowers and fruit and its stems armed with 

long spines. Devil's walking stick grows smaller and its leaves are very large and 

compound with numerous ovate leaflets. 

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: The common name castor aralia arose from 

its leaves resembling castor bean (Ricinus communis).

Look-alike: sweetgum 

(Mohamed Rezk)
82 New Invaders of the Northeast and Northcentral United States WHITE FLOWERS

Kousa dogwood

Cornus kousa F.Bürger ex Hance

SYNONYMS: kousa, Japanese dogwood

ORIGIN: East Asia

GROWTH TRAITS: Small deciduous tree or large multi-stemmed shrub typically 

growing 15-30' (4.5-9 m) tall from a far-reaching but shallow root system. Plants 

at first produce a vase-shaped canopy with upright branches, though branching 

becomes more horizontal and tiered with age, gradually creating a rounded canopy. 

Bark is grayish-brown and may begin peeling at maturity. Leaves are opposite, 

2-4" (5-10 cm) long, up to 1" (2.5 cm) wide, and attached to the branch with 

long petioles. Leaves are ovate to elliptical and have smooth but sometimes wavy 

margins and veins that curve towards the tip. Leaves are shiny green at first and 

turn pink in autumn before falling to the ground for winter. Flowers are produced 

in late spring to early summer, arising upright from leaf axils all along branches. 

Flowers are tiny, green, and non-showy in central clusters. They are surrounded 

by 4 showy white bracts that resemble petals. Each bract is 1-2" (2.5-5 cm) long 

and ovate with a pointed tip. The fruits are berry-like pendants typically 1.2" (3 

a b

Kousa dogwood a. tree; b. bark (a. A. Engelhardt; b. Dalgial)
New Invaders of the Northeast and Northcentral United States 83

Family Cornaceae

c d e

Kousa dogwood c. leaves; d. flowers; e. mature fruits (c. © Murodilla Fatkhullaev, iNaturalist.org; d. © 

belvedere04, iNaturalist.org; e. Velella)

cm) across that resemble large raspberries when ripe. Trees generally live 15 years 

in cultivation but many live much longer in their native habitat.

REPRODUCTION: Spreads by seed. Many seeds 

remain viable for up to 3 years.

HABITAT: Capitalizes on disturbance or intentional 

planting to establish initially, but can then spread 

into undisturbed areas. It grows well in full sun to 

partial shade and prefers moist, well-drained soil. In 

North America, it can be found on forest margins 

and abandoned lands and in urban gardens.

LOOK-ALIKES: The opposite leaves with veins 

curving toward the tip, in combination with the 

non-showy flowers surrounded by 4 showy white 

bracts, help differentiate this species from most potential look-alikes. The native 

flowering dogwood (Cornus florida) has similar growth form, leaves, and flowers. 

It differs with its flower bracts being rounded and notched at the tips, flowering 

earlier, and having clusters of smaller berry-like fruits that resemble rose hips 

rather than raspberries.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: Kousa dogwood is a popular ornamental 

that has escaped cultivation. Fruits are edible and 

sweet and are sometimes used in wine making.

Look-alike: flowering dogwood 

(John Ruter, University of 

Georgia, bugwood.org)
84 New Invaders of the Northeast and Northcentral United States YELLOW FLOWERS

Common daffodil

Narcissus pseudonarcissus L.

SYNONYMS: wild lent lily, Tenby daffodil, trumpet narcissus, wild daffodil

ORIGIN: Europe

GROWTH TRAITS: Herbaceous perennial that grows 8-18" (20-45 cm) tall 

from a bulbous root system. Leaves and flowers appear from March to May. All 

leaves are basal, emerging from the plant base. Leaves are grayish-green, leathery, 

and have smooth margins and rounded tips. Leaves are very linear; they can be 

as tall as the flower stem (18" or 45 cm) but are typically only 0.2-0.5" (0.5-

1.3 cm) wide. Flowers are generally produced individually on long, delicate, 

finely grooved, and leafless stalks. Each flower consists of a dark yellow 'trumpet' 

surrounded by a ring of 3 petals and 3 petal-like structures, which are a slightly 

lighter yellow and often twisted. The trumpet is up to 2.4" (6 cm) long, and the 

ring is up to 2.4" (6 cm) across. The fruits are capsules that split at maturity to 

release small, brown, and somewhat triangular seeds. When plants germinate 

from seeds, flowering often does not occur for 5-7 years. 

a b

Common daffodil a. plants; b. infestation (a. Dirtywilly, William Sandras; b. Sapin88)
New Invaders of the Northeast and Northcentral United States 85

Family Amaryllidaceae

c d e e

Common daffodil c. leaves; d. flowers; e. opened fruits and seeds (c. Krzysztof Golik; d. BerndH; e. 

Roger Culos)

REPRODUCTION: Spreads by seed and sprouting from bulbs. Seeds remain 

viable for at least two years; bulb longevity is typically less than 12 months. 

HABITAT: Common daffodil capitalizes on disturbance and typically spreads 

within and from ornamental gardens. It grows in partial shade to full sun and 

tolerates a variety of soils, though it grows best in well-drained soil. In North 

America it can be found in meadows, fields, woodlands, roadsides, and other 

disturbed areas adjacent to intentional plantings.

LOOK-ALIKES: While many bulbed flowers have 

leaves similar to common daffodil, most potential 

look-alikes lack the open trumpet and symmetrical 

ring on their flowers. Other exotic species of 

Narcissus have been introduced to North America. 

Most of these can be differentiated by having 

much shorter trumpets and/or white petal rings. 

Jonquil (N. jonquilla) has a yellow trumpet and 

petal ring, but it differs in having narrow leaves, a 

much shorter trumpet, and a very long tube at the 

base of the flower.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: The leaves, stems, seed pods and bulbs all 

contain toxic alkaloids that cause illness if ingested.

Look-alike: jonquil (Gustav 

Svensson)
86 New Invaders of the Northeast and Northcentral United States YELLOW FLOWERS

Dalmatian toadflax

Linaria dalmatica (L.) Mill.

SYNONYMS: broad-leaved toadflax, Linaria genistifolia (L.) Mill., L. genistifolia 

(L.) Mill. ssp. dalmatica (L.) Maire & Petitm.

ORIGIN: Eurasia

GROWTH TRAITS: Herbaceous perennial typically growing numerous upright 

and prostrate stems 1-4' (0.3-1.2 m) tall from a deep taproot with lateral branches. 

Leaves are alternate, leathery, green to blue-green, and often have a waxy surface. 

Leaves are heart-shaped at the base, clasp the stem, and are typically 1-2" long 

(2.5-5.0 cm) and nearly as wide. Flowers are bright yellow and snapdragon-like 

with a distinct upper and lower lip and a long spur pointing downward. Each 

has a fuzzy, yellowish-orange throat and is 1.4-2" (3.5-5 cm) long, including the 

spur. Flowers occur in spiked clusters emerging from leaf axils and branch tips 

throughout summer. Each flower produces a round capsule fruit holding several 

small, brown, and somewhat triangular seeds.

a b

Dalmatian toadflax a. plant; b. infestation (a. K. George Beck & James Sebastian, Colorado State 

University, bugwood.org; b. Jennifer Andreas, Washington State University Extension)
New Invaders of the Northeast and Northcentral United States 87

Family Plantaginaceae

c d e

Dalmatian toadflax c. leaves; d. flower; e. fruits (c,d. Bonnie Million, National Park Service, 

bugwood.org; e. Linda Wilson)

REPRODUCTION: Spreads by seed and root fragments. Seeds may remain 

viable in the soil for up to 10 years. 

HABITAT: Dalmatian toadflax is often found in or 

along disturbed areas such as railroads, roadsides, 

riversides, abandoned pastures and fields, and open 

forest slash piles. It does well in cool, semiarid 

climates and on coarse-textured soils.

LOOK-ALIKES: The combination of yellow, 

snapdragon-like flowers and waxy, heart-shaped 

leaves help differentiate Dalmatian toadflax from 

most potential look-alike species. The exotic myrtle 

spurge (Euphorbia myrsinites) has similar leaves, but 

myrtle spurge stems lean over instead of growing 

upright, they produce a milky sap when wounded, 

and they have typical spurge-type flowers that are green, inconspicuous, and 

surrounded by yellow-green bracts. The related and cultivated yellow snapdragon 

(Antirrhinum majus) has similar flowers and size, but its leaves are toothed and 

not waxy. The exotic yellow toadflax (L. vulgaris) also has similar flowers, but its 

leaves are narrow-linear and not waxy. Dalmatian and yellow toadflax are highly 

variable in North America and can hybridize.

NOXIOUS WEED LISTINGS: MN (Noxious 

Eradicate), WI (Restricted)

NOTES: Dalmatian toadflax is very problematic in 

the midwestern and western USA.

Look-alike: yellow snapdragon 

(Acabashi)
88 New Invaders of the Northeast and Northcentral United States YELLOW FLOWERS

Fig buttercup

Ficaria verna Huds.

SYNONYMS: lesser celandine, pilewort, Ranunculus ficaria L.

ORIGIN: Europe, the Mediterranean, temperate Asia

GROWTH TRAITS: Herbaceous, perennial groundcover plant that grows up 

to 12" (30 cm) tall from thick tuberous roots with tubers and bulblets. Some 

individuals also produce bulblets in leaf axils. It is a spring ephemeral, sprouting 

in late winter, flowering in March and April and dying back to its roots by 

the end of spring. Leaves are produced in a basal rosette and are up to 2" (5 

cm) long and wide with wavy margins and long petioles. Leaves are dark green 

above, lighter below, shiny, thickened, and kidney- to heart-shaped. Flowers are 

produced individually on long, delicate stalks that rise above the leaves. Flowers 

typically have 8 (sometimes up to 12) bright yellow and glossy petals and are 

usually 1" (2.5 cm) in diameter. Each flower produces up to 15 seeds that are 

hairy and tipped with bristles. 

a b

Fig buttercup a. plant; b. infestation (a. Krzysztof Ziarnek, Kenraiz; b. John M. Randall, The Nature 

Conservancy, bugwood.org)
New Invaders of the Northeast and Northcentral United States 89

Family Ranunculaceae

c d e f

Fig buttercup c. upper and lower sides of leaves; d. flower; e. fruits; f. bulblets (c. Janie Marlow, 

NameThatPlant.net; d. Greene Storm, St. John's University; e. Stefan.lefnaer; f. David L. Clement, 

University of Maryland; c,d,f bugwood.org)

REPRODUCTION: Spreads by seed, tubers, and bulblets. Seeds remain viable 

for at least 18 months; tuber and bulblet longevity is unknown. 

HABITAT: Typically found in moist areas, including forested floodplains, damp 

meadows, and along streams and ditches.

LOOK-ALIKES: The native marsh marigold 

(Caltha palustris) grows in similar habitat and has 

similar glossy yellow flowers and kidney-shaped 

leaves with wavy margins. It differs by having fewer 

petals (5-9), not producing tubers or bulblets, and 

growing in clumps instead of a continuous carpet 

like fig buttercup. Extreme care should be used 

when managing fig buttercup to ensure it is not 

the native and rare marsh marigold. The native 

celandine poppy (Stylophorum diphyllum) and 

exotic celandine (Chelidonium majus) also have 

similar habitat, flowers, and growth form. Both of 

these potential look-alikes differ by having divided 

leaves and flowers with only four petals.

NOXIOUS WEED LISTINGS: CT, IL, MA, NY, 

and WI (all Prohibited), MD (Tier 1)

NOTES: Fig buttercup was introduced to North 

America as an ornamental. It is poisonous if ingested 

raw and potentially fatal to grazing animals.

Look-alike: marsh marigold 

(Linda Haugen, USDA Forest 

Service, bugwood.org)
90 New Invaders of the Northeast and Northcentral United States YELLOW FLOWERS

Oldwoman

Artemisia stelleriana Besser

SYNONYMS: dusty miller, beach wormwood, hoary sagebrush

ORIGIN: East Asia, Alaska (western tip of Aleutian islands)

GROWTH TRAITS: Herbaceous perennial typically growing one to several 

upright stems up to 2' (60 cm) tall from a rhizomatous root system. Leaves 

are alternate, silver-gray, 1.2-4" (3-10 cm) long by up to 1" (2.5 cm) wide, and 

covered in woolly hairs that give leaves a velvety texture. Leaves generally have 

deep, rounded, but variable lobes along their margins and are often aromatic. 

Numerous flower heads are tightly clustered at the tips of flowering stems from 

late summer to early fall. Flower heads are 0.3" (8 mm) across and consist of tiny 

yellow disc florets. Each floret produces a tiny brown seed. 

REPRODUCTION: Spreads by seed and rhizomes. Most seeds are viable for 

only one year. 

a b

Oldwoman a. plant; b. infestation (a,b. © Lewnanny Richardson, iNaturalist.org)
New Invaders of the Northeast and Northcentral United States 91

Family Asteraceae

c d e

Oldwoman c. leaves; d. flower heads; e. senescing heads with seeds (c. David J. Stang; d. 

Qwert1234; e. © George Safford Torrey Herbarium [CONN])

HABITAT: Does best in sandy soils in full sun and can be found on coastal beaches 

and cliffs, sand dunes, and disturbed sites with well-drained soil. It tolerates 

drought well.

LOOK-ALIKES: The combination of silver-gray, 

woolly, and lobed leaves, non-showy flower heads 

with tiny disc florets, and aromatic foliage help 

differentiate oldwoman from many unrelated 

look-alikes. Within the genus, many species 

lack the silver-gray, woolly foliage. Most of the 

similar-looking species occur only in western 

North America. In the East, the exotic absinthe 

wormwood (A. absinthium) grows larger and has 

more finely divided leaves and fibrous roots. The 

native white sagebrush (A. ludoviciana) has more 

pointed leaves, its flower heads droop, and its 

crushed leaves have a strong camphor odor. 

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: Oldwoman is still popular in the 

ornamental trade for its attractive foliage capable 

of growing in dry, sandy locations. It frequently 

escapes cultivation.

Look-alike: absinthe 

wormwood (AfroBrazilian)
92 New Invaders of the Northeast and Northcentral United States YELLOW FLOWERS

Tansy ragwort

Jacobaea vulgaris Gaertn.

SYNONYMS: ragwort, tansy, stinking Willy, Senecio jacobaea L.

ORIGIN: Europe, Eurasia, the Mediterranean

GROWTH TRAITS: Upright, herbaceous plant typically growing 1-3' (0.3-

1 m) tall from a soft, fleshy root system. Where winters are mild, the plant 

typically acts as a biennial. Rosettes grow during winter, remain as rosettes the 

following year, bolt the second spring, and flower from summer to early fall 

before dying in winter. Flowering may occasionally occur the first year (winter 

annual), but is usually delayed until the second. At locations with harsh winters 

and shorter growing seasons, the plant may behave as a short-lived perennial. 

Rosette leaves are deeply lobed with wrinkled and round-toothed margins, have 

petioles, and are 3-8" (7.5-20 cm) long. Stem leaves are alternate, more deeply 

divided and toothed, and further up they stem they decrease in size and clasp 

the stem. Stems arise singly or in clumps and branch near the top with multiple 

inflorescences. Flower heads are 0.5-1" (1.3-2.5 cm) across and consist of tiny 

a b

Tansy ragwort a. plant; b. infestation (a. Jennifer Andreas, Washington State University Extension; 

b. Leslie J. Mehrhoff, University of Connecticut, bugwood.org)
New Invaders of the Northeast and Northcentral United States 93

Family Asteraceae

c d e f

Tansy ragwort c. rosette leaf; d. stem leaf; e. flower head with disc (center) and ray (outer, petal-like) 

florets; f. mature seeds (c,d. Marianna Szucs, Colorado State University; e. Strobilomyces; f. Rasbak)

yellow disc (center) and ray (outer) florets. Ray florets (usually 13) resemble 

petals and grow 0.3-0.75" long (0.8-2 cm) long. Brown seeds are topped by tufts 

of silky hairs, resembling dandelion seeds.

REPRODUCTION: Spreads primarily by seed but 

shoots may also sprout from damaged roots and 

root fragments. Seeds may remain viable in the soil 

for up to 15 years. 

HABITAT: Tansy ragwort tolerates partial shade but 

grows best in full sun in lighter, well-drained soils. 

It can be found in pastures, coastal grasslands, 

forest margins and clearings, roadsides, burned 

areas, and other disturbed places.

LOOK-ALIKES: Several native and exotic species 

of related Packera and Senecio resemble tansy ragwort with their flower heads 

containing both ray and disc florets. Most of these potential look-alikes do 

not have the same large size, large, deeply lobed, and rounded leaves, and large 

flower heads as tansy ragwort. The exotic common tansy (Tanacetum vulgare) has 

divided leaves and yellow flower heads, but common tansy has disc florets only.

NOXIOUS WEED LISTINGS: CT and MA 

(Prohibited)

NOTES: All parts of tansy ragwort contain 

pyrrolizidine alkaloids, substances that are broken 

down into compounds toxic to livestock and deer. 

Look-alike: common tansy 

(Matt Lavin, Bozeman MT)
94 New Invaders of the Northeast and Northcentral United States YELLOW FLOWERS

Yellow hornpoppy

Glaucium flavum Crantz

SYNONYMS: horned poppy, sea poppy, bruisewort, Glaucium luteum Scopoli, 

Chelidonium glaucium L.

ORIGIN: Eurasia, the Mediterranean

GROWTH TRAITS: Herbaceous biennial to short-lived perennial typically 

growing 1-3' (0.3-0.9 m) from a stout taproot. Leaves are blue-green, hairy, and 

sometimes waxy and leathery. They are 3-8" (7.5-20 cm) long, 1-2" (2.5-5 cm) 

wide, and deeply lobed with wrinkled margins, often appearing scrunched. Basal 

leaves have petioles; stem leaves are alternate, and further up they stem they 

decrease in size and clasp the stem. Flowers occur on stout stalks arising from 

leaf axils or stem tips throughout summer. Each flower is 2-3" (5-9 cm) across, 

has several yellow stamens, and has 4 yellow obovate petals that overlap and have 

wrinkled margins. Each flower produces a rough capsule fruit 6-12" (15-30 cm) 

long that holds several seeds. 

a b

Yellow hornpoppy a. plant; b. infestation (a. Haplochromis; b. Leslie Mehrhoff, University of 

Connecticut, bugwood.org)
New Invaders of the Northeast and Northcentral United States 95

Family Papaveraceae

c d e

Yellow hornpoppy c. leaves; d. flower; e. flower, fruit, and leaf segments (c. Jerzy Opioła; d. Peter A. 

Mansfeld; e. © Lisa Bennett, iNaturalist.org)

REPRODUCTION: Spreads by seed. Seeds may remain viable in the soil for at 

least three years. 

HABITAT: Yellow hornpoppy grows best in coarse, 

well-drained soils and full sun. It can be found on 

beaches above the high tide line as well as sand 

dunes and cliff tops.

LOOK-ALIKES: The combination of 4-petal 

yellow flowers, heavily divided leaves, and capsule 

fruit help differentiate yellow hornpoppy from 

most unrelated look-alikes. Within the family, the 

native celandine poppy (Stylophorum diphyllum) 

and exotic celandine (Chelidonium majus) have 

similar flowers and their leaves are also divided, but 

their leaves are more flat (rather than scrunched) 

compared to yellow hornpoppy, and their capsule 

fruits are much shorter. 

NOXIOUS WEED LISTINGS: MA (Prohibited)

NOTES: This species has likely been introduced 

to North America multiple times, both in ship's ballast and as intentional 

horticultural plantings.

Look-alike: celandine poppy 

(David Mortensen)
96 New Invaders of the Northeast and Northcentral United States YELLOW FLOWERS

Wintergreen barberry

Berberis julianae C.K. Schneid.

SYNONYMS: Chinese barberry

ORIGIN: China

GROWTH TRAITS: Evergreen shrub typically growing 4-8' (1.2-2.4 m) tall 

and equally wide from an extensive fibrous root system. Multiple branched stems 

give the plant an overall rounded appearance. New stem growth is pale yellow 

while older branches are more grayish-brown and often grooved. Stems have 3 

spines 0.4-1.6" (1-4 cm) long at each leaf node. Leaves are alternate or appear 

whorled at each node. Each leaf is shiny dark green, leathery, 1.2-4" (3-10 cm) 

long by 0.5" (1.3 cm) wide, elliptical or obovate, and has spiny margins. Leaves 

often turn a deep bronze or wine red in the fall and winter. Flowers appear in 

clusters of up to 25 from leaf axils in spring. Each flower is less than 0.5" (1.2 

cm) across and typically has 6 yellow petals and 6 yellow petal-like sepals. Berry 

fruits are oblong, up to 0.3" (8 mm) long, and covered with a waxy silver-blue 

that eventually wears off to reveal the black fruit beneath.

a b

Wintergreen barberry a. plant; b. infestation (a. John Ruter, University of Georgia, bugwood.org; b. 

Wouter Hagens)
New Invaders of the Northeast and Northcentral United States 97

Family Berberidaceae

c d e

Wintergreen barberry c. leaves, stem, flowers, and spines; d. flowers; e. fruit (c. Wouter Hagens; d. 

Denis.prévôt; e. © Carrie Seltzer, iNaturalist.org)

REPRODUCTION: Spreads by seed. Seeds are typically viable in the soil for up 

to one year. 

HABITAT: Wintergreen barberry can tolerate a 

variety of conditions. It is most limited by waterlogged soil. It tolerates partial shade but grows best 

in full sun, and is very cold tolerant. It can be found 

in abandoned fields, forests and forest clearings, 

floodplains, roadsides, and urban landscapes.

LOOK-ALIKES: The glossy green, leathery, spiny, 

evergreen leaves in combination with small yellow 

flowers and shrubby growth helps differentiate 

wintergreen barberry from unrelated look-alikes. 

There are several native and exotic species and 

cultivars of Berberis present in North America. 

Many that have similar foliage to wintergreen barberry have compound 

leaves. The native American barberry (B. canadensis) and the exotic Japanese 

(B. thunbergii) and European barberry (B. vulgaris) are most similar but are 

deciduous and have smaller stem spines, generally smaller and more rounded 

leaves, and fruits that are red at maturity rather than black.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state. 

NOTES: This species was intentionally introduced 

to North America as an ornamental, and it is still 

frequently utilized horticulturally as a hedge plant.

Look-alike: Japanese barberry 

(Alpsdake)
98 New Invaders of the Northeast and Northcentral United States AQUATIC PLANTS

Bog bulrush

Schoenoplectiella mucronata (L.) J.Jung & H.K.Choi

SYNONYMS: ricefield bulrush, rough-seed bulrush, Schoenoplectus mucronatus 

(L.) Palla ex A. Kern., Scirpus mucronatus L.

ORIGIN: Africa, Asia, Australia, Europe

GROWTH TRAITS: Annual (with fibrous roots) or perennial (with short, 

hard rhizomes) sedge that forms clumps 1-3’ (0.6-0.9 m) tall. True leaves are 

barely noticeable; they are reduced to small sheaths that encase the bottoms of 

stems. Stems are triangular in cross-section and may droop slightly. Clustered 

inflorescences of 4-25 cone-shaped spikelets occur just below stem tips. An 

angled, stiff bract extends from inflorescences and may resemble a continuation 

of the stem. Stems and bracts are bright green with smooth, straight margins. 

Flowers are green at first but mature to brown and bloom summer to fall. They 

are followed by small, bulb-shaped seeds ('nuts') that have tiny, thin bristles and 

mature to dark brown. 

a b

Bog bulrush a. plants; b. infestation (a. © Bob O'Kennon, iNaturalist.org; b. Wibowo Djatmiko, 

Wie146)
New Invaders of the Northeast and Northcentral United States 99

Family Cyperaceae

c d e

Bog bulrush c. stems; d. inflorescences and angled bract; e. bristled seeds (c. Wibowo Djatmiko, 

Wie146; d. © Bob O'Kennon, iNaturalist.org; e. Steve Hurst, USDA-NRCS PLANTS Database)

REPRODUCTION: Spreads by seed and rhizomes. Seeds may remain viable in 

the soil for many years. 

HABITAT: Bog bulrush is a weed of wet and boggy 

areas that can also grow in shallow water. It is 

found in disturbed and early successional wetlands 

and wetland restorations and along the margins of 

lakes and rivers. Plants grow best in full sun. 

LOOK-ALIKES: The triangular stems, non-showy 

green flowers that mature to brown, and nut-like 

fruit are all characteristic of the sedge family and 

help differentiate bog bulrush and other sedges 

from similar, unrelated species. Within the family, 

the cone-like spikelets and bristled fruits help 

differentiate bog bulrush from other sedges. The 

native Hall's bulrush (Schoenoplectiella hallii), 

weakstalk bulrush (S. purshiana), and Smith's bulrush (S. smithii) all have 

shorter and more delicate stems that droop much more. The native common 

threesquare (Schoenoplectus pungens) has similar stems, but its inflorescences 

have much longer stamens, and the bract extending from the inflorescence is 

not angled as it is for bog bulrush.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state. 

NOTES: Around the world, bog bulrush is a 

frequent weed in rice fields. 

Look-alike: common 

threesquare (Rob Routledge, 

Sault College, bugwood.org)
100 New Invaders of the Northeast and Northcentral United States AQUATIC PLANTS

Variable flatsedge

Cyperus difformis L.

SYNONYMS: smallflower umbrella sedge, rice sedge, small-flowered nutsedge

ORIGIN: Africa, Asia, Australia, Europe

GROWTH TRAITS: Annual, aquatic sedge growing 3-32" (7.5-81 cm) tall from a 

fibrous root system. Stems are, smooth, erect, slightly winged, triangular in crosssection, and up to 0.12" (3 mm) thick. Leaves are basal, flat, linear, generally up 

to 2/3 the length of the stems, and up to 0.25" (6 mm) wide. Leaves are typically 

smooth, but may be slightly rough along their center or margins. Inflorescences 

are loose umbels with numerous globular clusters of 10-60 spikelets. Flowers are 

green at first but mature to brown. Beneath each inflorescence are 1-4 leaf-like 

bracts that are angled away from plant stems. Bracts are 10" (25 cm) long and 

resemble stiff leaves. Flowers are followed by small, triangular fruits ('nuts') that 

mature to light brown. Plants can complete their life cycle from seed to seed 

within a month. In warm climates, seed production continues year-round; in 

temperate areas, seed production is restricted to spring through fall.

a b

Variable flatsedge a. plant; b. infestation (a. Forest & Kim Starr, Starr Environmental; b. Charles T. 

Bryson, USDA ARS, bugwood.org)
New Invaders of the Northeast and Northcentral United States 101

Family Cyperaceae

c d e

Variable flatsedge c. bract that resembles a leaf d. inflorescence; e. tiny green (immature) flowers 

(c,e. Nadiah Vololomboahangy Manjato; d. Charles Rakotovao; c-e. tropicos.org)

REPRODUCTION: Spreads by seed. Seeds may remain viable in the soil for 

many years. 

HABITAT: Variable flatsedge is a weed of wet 

and boggy areas and can grow in shallow water, 

including wetlands and along the margins of lakes 

and rivers. Plants can also invade upland areas with 

moist soil and grow best in full sun. 

LOOK-ALIKES: The triangular stems, non-showy 

green flowers that mature to brown, and nut-like 

fruit are all characteristic of the sedge family and 

help differentiate variable flatsedge and other 

sedges from similar, unrelated species. There are 

several native and exotic Cyperus species present in 

the USA which resemble variable flatsedge in their 

immature stages. Variable flatsedge can be differentiated during flowering by its 

globular, tightly packed clusters of 10-60 spikelets. Other Cyperus species, such 

as the native drain flatsedge (Cyperus eragrostis), have non-spherical clusters or 

their spikelets are fewer in number.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state. 

NOTES: Though its distribution in the USA is 

currently low, variable flatsedge is considered 

one of the world's worst weeds, being a frequent 

invader in rice, sugarcane, tea, and maize.

Look-alike: drain flatsedge 

(John Tann)
102 New Invaders of the Northeast and Northcentral United States AQUATIC PLANTS

European frog-bit

Hydrocharis morsus-ranae L.

SYNONYMS: common frogbit

ORIGIN: Europe, Eurasia, the Mediterranean

GROWTH TRAITS: Herbaceous, aquatic perennial with a fibrous root system 

that is unbranched and free-floating (not anchored to the sediment). Leaves are 

bright shiny green above and either green or dark purple beneath, leathery, and 

have a thick spongy layer on their undersides near the midvein that helps them 

float. Leaves are round or heart-shaped with an indented base, 0.5-2.4" (1-6 cm) 

wide, and have long slender petioles and veins all arising from the indented base. 

The plant sends out stolons that can float on water and produce new rosettes 

with leaves and submerged roots. This often leads to dense mats forming on 

pond or lake surfaces. Flowers are produced throughout summer on long stalks. 

Male and female flowers occur on separate plants, or at least separate rosettes. 

Male flowers occur in clusters of 1-5 while female flowers occur singly on longer 

stalks. Both types of flowers have 3 membranous white petals and yellow centers 

and are 0.4-0.8" (1-2 cm) across. Though uncommon, fruits are berry-like and 

a b

European frog-bit a. plants; b. infestation (a,b. Christian Fischer)
New Invaders of the Northeast and Northcentral United States 103

Family Hydrocharitaceae

c d e

European frog-bit c. leaves; d. turion; e. flowers (c-e. Christian Fischer)

contain seeds up to 0.04" (1 mm) long. In the fall, stolons produce green, oval 

turions (winter buds) up to 0.25" (7 mm) long. These sink over winter and float 

in spring, giving rise to new plants.

REPRODUCTION: Despite flowering profusely, spread by seed is uncommon. 

Most population spread is via stolons and turions. Seed longevity is unknown.

HABITAT: Does best in slowly moving water 

including ponds and marshes and along the 

protected banks of streams and lakes.

LOOK-ALIKES: The 3-petal white flowers and 

small, round, heart-shaped leaves help differentiate 

this species from most potential look-alikes. The 

native American frogbit (Limnobium spongia) has 

similar leaves but has ridged petioles, flowers that 

appear fringed, and leaves with the spongy layer 

in a central disk rather than near the midvein. The 

native little floating heart (Nymphoides cordata) has 

5-petal flowers. Water lilies (Nymphaea spp.) have 

larger leaves and larger, layered flowers.

NOXIOUS WEED LISTINGS: IL (Aquatic 

Injurious Plant), IN and NH (Prohibited Aquatic), 

ME (Noxious), MI, NY, and WI (all Prohibited), 

VT (Noxious B)

NOTES: This species is popular in the aquarium trade, and many wild populations 

in the USA are the result of inappropriate aquarium dumping. 

Look-alike: American frogbit 

(Chris Evans, University of 

Illinois, bugwood.org)
104 New Invaders of the Northeast and Northcentral United States AQUATIC PLANTS

European speedwell

Veronica beccabunga L.

SYNONYMS: European brooklime

ORIGIN: Asia, Europe, the Mediterranean

GROWTH TRAITS: Emergent, herbaceous aquatic perennial that is rooted to 

the substrate with branched stems growing 8"-2' (20-60 cm) long and forming 

creeping clumps by regularly rooting at stem nodes. Stems are smooth, thick, 

often prostrate but erect at their tips, and green but turning reddish with maturity. 

Leaves are opposite, ovate, coarsely toothed, smooth, often fleshy, and have 

prominent veins. Leaves are up to 1.5" (3.8 cm) long and have short petioles; 

they do not clasp the stem. Flowers are produced in small, spreading clusters 

in opposite pairs from leaf axils in spring and early summer. These are often 

obscured by larger leaves. Each flower has 4 small, bluish-purple, darkly-veined 

petals and a white center. Fruits are small, round, flattened capsules that split 

at maturity to release numerous smooth, winged, flattened seeds. In temperate 

regions, plants die back to roots and may re-sprout the following spring.

a b

European speedwell a. plant; b. infestation (a. © Drepanostoma; b. © anohturfft; a,b. iNaturalist.org)
New Invaders of the Northeast and Northcentral United States 105

Family Plantaginaceae

c d e

European speedwell c. leaves; d. flowers; e. fruits (c. © Pat Deacon, iNaturalist.org; d. TeunSpaans; 

e. © 2017 Paul Busselen, gobotany.newenglandwild.org)

REPRODUCTION: Spreads by seed and fragmentation. Seed longevity is 

unknown, but seeds of other Veronica species are viable for three to many years. 

Stem fragments root from nodes.

HABITAT: Colonizes marshy wetlands and the edges of rivers, lakes, and streams. 

It can be found in full sun to partial shade.

LOOK-ALIKES: Though many other aquatic 

species have emergent purplish flowers and/

or opposite leaves, European speedwell can be 

differentiated by having 4-petal flowers with white 

centers, and relatively short leaves than most 

unrelated look-alikes. There are several native 

and exotic species of Veronica in North America. 

European speedwell differs from many in being 

aquatic with smooth stems. The very similar native 

American speedweel (V. americana) often grows 

taller (up to 3.3' or 1 m), has longer, lance-shaped 

leaves up to 3.2" or 8 cm long, and its petioles are 

so short that leaves often appear to clasp the stem.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any northeastern/northcentral state.

NOTES: This species was likely accidentally 

introduced into the continental United States in 

the 1880s in ship's ballast.

Look-alike: American speedwell 

(Rob Routledge, Sault College, 

bugwood.org)
106 New Invaders of the Northeast and Northcentral United States AQUATIC PLANTS

European waterstarwort

Callitriche stagnalis Scop.

SYNONYMS: pond water-starwort, common waterstarwort, water chickweed

ORIGIN: Asia, Europe, the Mediterranean

GROWTH TRAITS: Herbaceous, aquatic perennial (sometimes annual) that is 

anchored in the sediment by slender, linear roots. Stems are flexible, 4-12" (10-

30 cm) long, and root from nodes. Leaves are bright green, opposite, thick, and 

have smooth margins. Floating and emergent leaves are oval to spoon-shaped, 

up to 0.8" (2 cm) long and nearly as wide, and are often crowded at stem tips. 

Floating leaves and stems often form dense mats at the water surface. Submerged 

leaves are typically more linear, up to 0.4" (1 cm) long, and more widely spaced. 

However, some submerged leaves more closely resemble the shape and size of 

floating leaves. Flowers are produced throughout summer in the leaf axils of 

both floating and submerged leaves. Flowers are tiny and have no petals, but 

have 2-4 small, white, inflated bracts. Fruits are nearly round, up to 0.08" (2 

a b

European waterstarwort a. plants; b. infestation (a. © Gerald D. Carr 2017; b. Leslie J. Mehrhoff, 

University of Connecticut, bugwood.org)
New Invaders of the Northeast and Northcentral United States 107

Family Plantaginaceae

c d e

European waterstarwort c. floating and emergent leaves; d. flowers and fruit from above; e. flowers 

and fruit in profile (c-e. © Gerald D. Carr 2017)

mm) long, and have 4 compartments. Each compartment has a tiny wing along 

its margin.

REPRODUCTION: Spreads by seed and fragmentation. Seed longevity is 

unknown. Stem fragments root from nodes.

HABITAT: Does best in slowly moving water 

including ponds and marshes and along the 

protected banks of streams and lakes.

LOOK-ALIKES: Multiple species of native and 

exotic waterstarworts are present in North America, 

including vernal waterstarwort (Callitriche 

palustris). Due to variability in leaf shape and size, all 

of these closely resemble European waterstarwort. 

Fruits are needed for proper identification; fruits 

of European waterstarwort differ by being nearly 

round and having tiny wings along the margins of 

the compartments.

NOXIOUS WEED LISTINGS: CT (Prohibited)

NOTES: This species was likely introduced via 

shipping contaminants. It was also popular in the 

aquarium trade by the end of the 19th century and 

likely became established in disjunct populations 

in the USA via the inappropriate dumping of 

aquarium contents. 

Look-alike: vernal waterstarwort, 

submerged (Show_ryu)
108 New Invaders of the Northeast and Northcentral United States AQUATIC PLANTS

Giant salvinia

Salvinia molesta D.S. Mitch.

SYNONYMS: watermoss, water fern, salvinia, kariba-weed, African pyle

ORIGIN: South America

GROWTH TRAITS: Aquatic, free-floating fern that grows as an annual or shortlived perennial and has no true roots. Horizontal branching rhizomes float just 

below the surface and bear three leaves (fronds) at each node. Two leaves are 

floating and one is submersed and divided into several filaments that resemble (but 

do not function as) roots. Floating leaves are oval-shaped and up to 1.6" (4 cm) 

long and have smooth margins and distinct midribs. Water repellent, white hairs 

on the upper surface of floating leaves have 4 branches that join back together at 

the tip, giving them an “egg beater” appearance. Hairs on the undersides of leaves 

and filaments are unbranched and chestnut-colored. Depending on nutrient and 

space availability, plants may be slender with small leaves or dense mats with large, 

crowded, folded leaves. Spore-producing structures (sporocarps) shaped like small 

eggs are arranged in chains on submersed filaments.

a b

Giant salvinia a. plant with crowded leaves; b. infestation (a. Leslie Mehrhoff, University of 

Connecticut; b. Kenneth Calcote, Mississippi Dept. of Agriculture and Commerce; a,b bugwood.org)
New Invaders of the Northeast and Northcentral United States 109

Family Salviniaceae

c d e

Giant salvinia c. floating leaves on a non-crowded plant; d. “egg beater” hairs on upper surface of 

floating leaf; e. senescing plant with rusty floating leaves and filaments with sporocarps (c,e. Leslie J. 

Mehrhoff, University of Connecticut; d. Mic Julien, CSIRO; c-e bugwood.org)

REPRODUCTION: Though sporocarps can be found on submersed filaments, 

this species is not known to produce fertile spores in the USA, and all reproduction 

occurs vegetatively via regular fragmentation of the rhizomes. 

HABITAT: Giant salvinia grows best in still, shallow 

water with high organic content where it often forms 

dense mats. It does not tolerate saline environments.

LOOK-ALIKES: There are at least four exotic species 

known as giant salvinia present in the USA, of 

which S. molesta is the most common; sporocarps 

are generally needed to tell them apart. The exotic 

and invasive common salvinia (Salvinia minima) is 

half the size of the giant salvinias, and its upper leaf 

hairs are free near the tips while the upper leaf hairs 

of giant salvinias come together at the tips. Native 

mosquitoferns (Azolla spp.) may superficially 

resemble giant salvinia. Mosquitofern plants are much smaller, typically less than 

1" (2.5 cm) wide with numerous tiny, overlapping leaves.

NOXIOUS WEED LISTINGS: CT, MA, MI, 

WI (all Prohibited), IL (Aquatic Injurious), IN 

(Prohibited Aquatic), VT (A), RI (Noxious), WV

NOTES: This species is frequently introduced via 

improper disposal of aquarium contents in natural 

settings or spreading from ornamental ponds. 

Look-alike: common salvinia 

branching hairs on leaf surface 

(Mic Julien, CSIRO)
110 New Invaders of the Northeast and Northcentral United States AQUATIC PLANTS

Mudmat

Glossostigma cleistanthum W.R. Barker

SYNONYMS: mudmats

ORIGIN: Australia, New Zealand

GROWTH TRAITS: Small herbaceous, aquatic that is anchored to the sediment 

by a rhizomatous root system. Plants grow either submerged in fresh water 

or emergent along shorelines. Rhizomes grow just below the soil surface and 

produce roots and two leaves at each node. Leaves are bright green, 0.4-1.2" (1-3 

cm) long, and spatula-shaped with rounded tips and smooth margins. Flowers 

are produced throughout summer. Flowers on emergent plants are tiny, bellshaped, and pinkish-white. They appear on slender stalks arising from rhizome 

nodes. On submerged plants, closed, self-fertilized flowers (cleistogams) are 

produced at rhizome nodes. Fruits are small capsules containing numerous tiny 

seeds. Emergent plants grow as annuals, dying back in the winter. Submerged 

plants are perennial, remaining green and producing fruit throughout winter.

REPRODUCTION: Spreads by seed and rhizomes. Seed longevity is unknown. 

a b

Mudmat a. plants; b. infestation (a,b. Leslie J. Mehrhoff, University of Connecticut, bugwood.org)
New Invaders of the Northeast and Northcentral United States 111

Family Phrymaceae

c d e

Mudmat c. leaves and flowers; d. plants, rhizomes, and cleistogams; e. flowers (c-e. Leslie J. 

Mehrhoff, University of Connecticut, bugwood.org )

HABITAT: Grows submerged or along sandy to muddy shorelines of freshwater 

lakes and rivers and fresh tidal reaches. When growing submerged, the clarity of 

the water determines its depth. It is typically restricted to shallow water, but has 

been found 13' (4 m) deep in very clear water.

LOOK-ALIKES: The small, spatula-shaped leaves 

and tiny whitish flowers of mudmat resemble 

those of native mudwort species, including water 

mudwort (Limosella aquatica). Water mudwort 

differs by having multiple leaves per plant (node), 

larger leaves, and flowers with 5 petals. Emergent 

leaves of some bladderwort species (Utricularia) 

may be confused for mudmat. Bladderworts can 

be differentiated by having larger yellow flowers.

NOXIOUS WEED LISTINGS: WI (Prohibited)

NOTES: This species was introduced to North 

America in the aquarium trade and likely became 

established in disjunct populations in the USA via 

the inappropriate dumping of aquarium contents. 

Look-alike: water mudwort 

(Mary Ellen (Mel) Harte)
112 New Invaders of the Northeast and Northcentral United States AQUATIC PLANTS

Onerow yellowcress

Nasturtium microphyllum Boenn. ex Rchb.

SYNONYMS: onerow watercress, Nasturtium officinale var. microphyllum (Boenn. 

ex Rchb.) Thell., Rorippa microphylla (Boenn. ex Rchb.) Hyl. ex Á. Löve & D. 

Löve, Rorippa nasturtium-aquaticum var. longisiliqua (Irmisch) B. Boivin

ORIGIN: Asia, Europe, the Mediterranean

GROWTH TRAITS: Herbaceous, perennial aquatic or semi-aquatic that is rooted 

to the substrate with a taproot and fibrous root system. Stems typically creep on 

soil or float on open water, growing up to 3.3' (1 m) long and forming sprawling 

clumps by regularly rooting at stem nodes. Stems are smooth, ridged, green, and 

hollow. Leaves are green (sometimes bronze),1-4" (2.5-10 cm) long, and divided 

into 3-7 leaflets. Leaflets are obovate with smooth or slightly wavy margins. 

The terminal leaflet is larger than the side leaflets. Stem leaves are alternate and 

decrease in size further up the stem. Flowers are produced in clusters at stem tips 

in spring and summer. Each flower is typically 0.25” (6 mm) in diameter and has 

4 small white petals and 6 stamens. Fruits are up to 1" (2.5 cm) long, thin, and 

a b

Onerow yellowcress a. plant; b. infestation (a. Leslie J. Mehrhoff, University of Connecticut, 

bugwood.org; b. © Colin Meurk, iNaturalist.org)
New Invaders of the Northeast and Northcentral United States 113

Family Brassicaceae

c d e

Onerow yellowcress c. leaves; d. flowers; e. fruits (c-e. Leslie Mehrhoff, U. of Connecticut, bugwood.org)

contain numerous tiny seeds that are generally in one row (sometimes a wavy row 

rather than a straight line). Fruits split at maturity to release seeds. In temperate 

regions, plants die back to roots and may re-sprout the following spring.

REPRODUCTION: Spreads by seed and fragmentation. Seeds are viable for up 

to five years. Stem fragments root from nodes.

HABITAT: Colonizes the edges of moving water and 

can be found in/along rivers, streams, ditches, and 

springs. It can be found in full sun to partial shade.

LOOK-ALIKES: Several related species are present 

in North America and resemble onerow yellowcress 

with their similar leaves and tiny flowers with 4 

petals and 6 stamens. Many look-alikes have yellow 

flowers and are terrestrial. The exotic watercress 

(Nasturtium offinale) most closely resembles onerow 

yellowcress by being aquatic and having white 

flowers. Watercress differs by growing larger and 

having seeds arranged in two rows within its fruit. 

NOXIOUS WEED LISTINGS: CT (Prohibited)

NOTES: Though not intentionally cultivated like 

the related watercress, onerow yellowcress is an 

important food source in some countries where it 

is native or long naturalized. It frequently carries the common liver fluke when 

growing in places near livestock grazing.

Look-alike: watercress (Matt 

Lavin, Bozeman MT)
114 New Invaders of the Northeast and Northcentral United States AQUATIC PLANTS

Yellow floatingheart

Nymphoides peltata (S. G. Gmel.) Kuntze

SYNONYMS: fringed water lily, water fringe

ORIGIN: Eurasia

GROWTH TRAITS: Herbaceous, aquatic perennial with a fibrous and 

rhizomatous root system that is anchored to the sediment. The plant sends 

out branched stolons up to 3.3' (1 m) long that produce new rosettes with 

leaves and submerged roots. This often leads to dense mats forming on pond 

or lake surfaces. Leaves are leathery, bright shiny green above, typically dark 

purple beneath, and have wavy margins. Leaves are round or heart-shaped with 

an indented base, 2-6" (5-15 cm) wide and long, and have long slender petioles 

that attach to stolons. Flowers are produced throughout summer on long stalks 

held above the water surface. Flowers are up to 1.6" (4 cm) in diameter and have 

5 yellow petals with fringed margins. Fruits are beaked capsules 0.5-1" (1.3-2.5 

cm) long that contain many flat, oval, winged seeds. In the fall, plants die back 

to the rhizomes, and new shoots emerge in spring.

a b

Yellow floatingheart a. plant; b. infestation (a. Krzysztof Ziarnek, Kenraiz; b. Rob Andress, bugwood.org)
New Invaders of the Northeast and Northcentral United States 115

Family Menyanthaceae

c d e

Yellow floatingheart c. leaves; d. flower; e. fruits (c-e. Leslie Mehrhoff, University of Connecticut, 

bugwood.org)

REPRODUCTION: Spreads by seed and stolons. Some seeds reportedly remain 

viable for over 10 years.

HABITAT: Does best in slowly moving water 

including ponds and marshes and along the 

protected banks of streams and lakes. This species 

can grow on damp mud but cannot grow in shade.

LOOK-ALIKES: The native pond lilies or 

spatterdocks (Nuphar spp.) have similar-shaped 

leaves and yellow flowers; however their leaves 

are much larger and their cup-like flowers lack 

fringed petals. The native water shield (Brasenia 

schreberi) has similar small, oval floating leaves, but 

often with a jelly like covering on the undersides, 

and it has small purple flowers. Other species of 

Nymphoides are smaller than yellow floatingheart 

and/or have white flowers, including the native 

little floating heart (Nymphoides cordata). Water 

lilies (Nymphaea spp.) have larger leaves and larger, 

layered flowers.

NOXIOUS WEED LISTINGS: CT, MA, MI, 

NY, WI (all Prohibited), IL (Aquatic Injurious Plant), IN and NH (Prohibited 

Aquatic), ME (Noxious), VT (Noxious B)

NOTES: This species is popular in water gardening, and many wild populations 

in the USA are the result of garden plants escaping into nearby water bodies.

Look-alike: Rocky Mountain 

pond lily (Paul Bolstad, University 

of Minnesota, bugwood.org)
116 New Invaders of the Northeast and Northcentral United States GLOSSARY

Glossary

Term Definition

achene A small, one-seeded fruit that does not split at maturity

alternate Where leaves appear singly at stem nodes, on 

alternate sides of the stem

annual A plant that completes its life cycle in one year and 

then dies

awn A hair- or bristle-like appendage extending from 

florets of many grasses

axil The angle between the upper side of a leaf or stem 

and the stem or branch that supports it

banner The upper petal of a pea flower (Fabaceae)

basal Located at the base of a plant or plant part

biennial A plant that flowers and then dies in its second year

bolting Plant stage at which the flower stalk begins to grow

bract A small, leaf-like structure below a flower

bulbil A small bulblike structure, often in the axil of a leaf 

or at the base of a stem, that may form a new plant

bulblet A bulb arising from another bulb and acting as a 

thick storage organ

compound leaf A leaf consisting of two or more leaflets borne on the 

same leaf stalk

corm Rootstock with a fleshy, swollen stem base that is 

usually underground and stores food reserves

cormel Smaller tuberous offshoots of corms

crown Location where a plant's stems meets its roots

deciduous Sheds its leaves annually

density Number of individuals per unit area (e.g. plants, 

stems, or leaves)

divided Synonym for compound leaf
New Invaders of the Northeast and Northcentral United States 117

Term Definition

elliptical Shaped like a flattened circle, symmetrical, tapering 

equally both to the tip and the base

erect Grows upright and vertical as opposed to prostrate 

(spreading on the ground)

exotic Not native 

floret One of the small, closely clustered flowers forming 

the head of a composite flower in the sunflower 

family or the flowering unit of a grass spikelet, 

consisting of the flower and its two enveloping bracts

flower head A special type of inflorescence consisting of a 

receptacle and numerous florets that actually look like 

one flower. Typical of plants in the sunflower family

forb Herbaceous plant (does not have solid woody stems)

herbaceous Does not have solid woody stems

hyperaccumulator A plant capable of growing in soils with very high 

concentrations of substances (usually metals or 

toxins), absorbing these substances through their 

roots, and concentrating extremely high levels of the 

substances in their tissues

inflorescence The flowering part of a plant

involucre A circle of bracts under an inflorescence

lag phase First stage of a typical plant invasion during which 

populations remain at low levels for several years. 

Plants often become abundant during the next phase

leaflet A leaf-like part of a compound leaf. Though it 

resembles an entire leaf, a leaflet is not attached to 

the main plant stem or branch as a leaf is, but rather 

on the leaf stalk

lenticels Raised pores in the stem of a woody plant that 

allow gas exchange between the atmosphere and the 

internal tissues

ligule A thin outgrowth at the junction of leaf and leafstalk 

of many grasses and sedges and some other species
118 New Invaders of the Northeast and Northcentral United States GLOSSARY

Term Definition

lobed A leaf with shallow or deep, rounded segments, as in 

a thistle rosette leaf

native A plant that originated in the geographic area of 

discussion

node Part of the stem of a plant from which a leaf, branch, 

or root grows

ochrea (pl. ochreae) A saucer-shaped structure that sheathes the stems of 

certain plants, formed from united stipules or leaf bases

opposite Where leaves appear in twos at stem nodes, on 

opposite sides of the stem

obovate Shaped like an upside-down egg with the tip wider 

than the base

ovate Shaped like an egg, with the base wider than the tip

perennial A plant that lives for more than two years

petiole Leaf stalk that attaches the leaf to a plant stem

prostrate Grows flat along the ground as opposed to growing 

erect (upright)

receptacle Part of the stem to which the flower is attached

recurved Curved backward or downward

rhizome A modified stem of a plant that grows horizontally 

underground, often sending out roots and shoots 

from its nodes

rosette A compact, circular, and normally basal cluster of leaves

samara An achene fruit with a flattened, papery wing

scarification Cutting the seed coat using abrasion, thermal stress, 

or chemicals to encourage germination

senescence Final stage in a plant’s life cycle

sepal Typically green segments occurring beneath flower 

petals that protect the flower in bud and petals when 

in bloom. Some may resemble petals
New Invaders of the Northeast and Northcentral United States 119

Term Definition

serrated Toothed with asymmetrical teeth pointing forward 

as in the cutting edge of a saw

sheath A tubular or rolled part of an organ, e.g. the lower 

part of the leaf in most grasses

spadix Inflorescence with several tiny flowers clustered on a 

narrow, fleshy stem

spathe Leaf-like curved bract, typically surrounding a spadix

stamen The pollen-producing reproductive organ of a flower

stolon Stem which grows at the soil (or water) surface or 

just below ground that forms adventitious roots at 

nodes, and new plants from buds (also called runner)

sporocarp A fruiting body containing spores

taxonomy The classification of organisms in an ordered system 

that indicates natural relationships. The science, 

laws, or principles of classification; systematics

toothed (margin) Saw-like leaf margin with teeth on the edge that may 

be different in size. Also called serrated

turion Bud that gives rise to a new plant after it breaks free 

from the parent plant and sprouts. May be on a 

stolon, leaf, or subterranean or submerged rootstock

tussock Tuft or clump of growing bunchgrass

umbel An inflorescence which consists of a number of short 

flower stalks which spread from a common point, 

somewhat like umbrella ribs. They can be simple or 

compound (the single flowers are replaced by many 

smaller umbels called umbellets)

variegated Plant foliage having leaves that are edged or patterned 

in a second color, especially white as well as green

whorled Where multiple leaves or flowers radiate outward 

from a single stem node

winter annual A plant that germinates in autumn, lives through winter, 

and produces seed and dies in the following season
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References for Plant Identification and Terminology

Elpel, T. J.. 2006. Botany in a day: the patterns method of plant identification. HOPS Press, LLC. 221 pp.

Go Botany: https://gobotany.newenglandwild.org/simple/

Harrington, H.D. and L.W. Durrell. 1957. How to Identify Plants. Swallow Press, Chicago, IL. 203 pp.

Wildflowers and Weeds: http://www.wildflowers-and-weeds.com/Plant_Families/Patterns_in_Plants.htm

References for Other Invasive Plants Already More 

Established in the Region

BugwoodWiki. Center for Invasive Species and Ecosystem Health, University of Georgia. Available 

online at https://wiki.bugwood.org/

EDDMapS. Early Detection & Distribution Mapping System. The University of Georgia - Center for 

Invasive Species and Ecosystem Health. Available online at http://www.eddmaps.org/

Gleason, H.A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and 

Adjacent Canada. Second Edition. New York Botanical Garden. 910 pp.

National Association of Invasive Plant Councils. Available online at https://www.na-ipc.org

National Invasive Species Information Center. Available online at https://www.invasivespeciesinfo.gov/

index.shtml

National Invasive Species Information Center: Information at the state level. Available online at https://

www.invasivespeciesinfo.gov/unitedstates/state.shtml

English to Metric Conversions (Length)

Symbol When You Know Multiply By To Find Symbol

in or ” inches 2.54 centimeters cm

ft or ’ feet 0.305 meters m

yd yards 0.914 meters m