NEW INVADERS OF THE NORTHWEST

Second Edition

Rachel Winston, Wendy DesCamp, Jennifer Andreas, 

Carol Bell Randall, Joseph Milan, and Mark Schwarzländer 

United States 

Department of Agriculture

TECHNOLOGY

TRANSFER

Forest Health Technology

Enterprise Team

University of Idaho

Extension

FHTET-2014-12

December 2014
The Forest Health Technology Enterprise Team (FHTET) was created in 

1995 by the Deputy Chief for State and Private Forestry, USDA, Forest 

Service, to develop and deliver technologies to protect and improve the health of 

American forests. This book was published by FHTET as part of the technology 

transfer series. 

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

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and 

activities on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, sexual 

orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with 

disabilities who require alternative means for communication of program information (Braille, large 

print, audiotape, etc.) should contact USDA’s TARGET Center at 202-720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, 

Whitten Building, 1400 Independence Avenue, SW, Washington, D.C. 20250-9410, or call 202-

720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.

The use of trade, firm, or corporation names in this publication is for the information and convenience 

of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department 

of Agriculture or the Forest Service of any product or service to the exclusion of others that may be 

suitable.

Cover photos (clockwise from top left): crown vetch (Dan Tenaglia, Missouriplants.com, www.bugwood.

org), garden loosestrife (King County NWCB), giant reed (Amy Ferriter, www.bugwood.org), blueweed 

(H. Zell), English holly (Jürgen Howaldt)

Federal Recycling Program

Printed on Recycled Paper
NEW INVADERS OF THE NORTHWEST

Second Edition

Rachel L. Winston

Environmental Consultant

MIA Consulting, LLC

Sandpoint, ID

rachel@getmia.net

Wendy DesCamp

Education Specialist

Washington State Noxious Weed Control Board

Olympia, WA

wdescamp@agr.wa.gov

www.nwcb.wa.gov

Jennifer E. Andreas

Integrated Weed Control Project

Washington State University Extension

Puyallup, WA

jandreas@wsu.edu

www.invasives.wsu.edu

Carol Bell Randall

Entomologist, Forest Health Protection

USDA Forest Service

Coeur d’Alene, ID

crandall@fs.fed.us

Joseph Milan

Biological Control Specialist

Bureau of Land Management

Boise, ID

jmilan@blm.gov

Mark Schwarzländer

Associate Professor for Entomology

University of Idaho, PSES Despartment

Moscow, ID

markschw@uidaho.edu

For additional copies of this publication, contact: 

Mark Schwarzländer

University of Idaho

PSES Department

Moscow, ID 83844

208.885.9319

markschw@uidaho.edu

Richard Reardon

USDA Forest Service

180 Canfield Street

Morgantown, WV 26505

304.285.1566

rreardon@fs.fed.us

Acknowledgments

Numerous state, provincial, and regional weed experts and land managers contributed their 

time and expertise to create the species list utilized in this guide. The distribution maps were 

compiled by Michelle Lewis. The distribution maps were compiled by Michelle Lewis. The 

layout was designed by Rachel Winston, with assistance from Wendy W. Harding. We would 

like to thank all of the photographers who granted permission for the use of photos. We also 

extend our gratitude to Richard Reardon (Forest Service-Forest Health Technology Enterprise 

Team or FHTET) for producing this guide.
Table of Contents 2 New Invaders of the Northwest

Introduction 4

Bluish-Purple Flowers 12

Blueweed, Echium vulgare 12

Clary sage, Salvia sclarea 16

Meadow clary, Salvia pratensis

Paterson’s curse, Echium plantagineum

16

12

Pine echium, Echium pininana 14

Silverleaf nightshade, Solanum elaeagnifolium 18

Green Flowers 20

Barbed goatgrass, Aegilops triuncialis 20

Chinese silvergrass, Miscanthus sinensis

Eggleaf spurge, Euphorbia oblongata

False brome, Brachypodium sylvaticum

22

32

24

Giant reed, Arundo donax 26

Japanese chaff flower, Achyranthes japonica

Jubata grass, Cortaderia jubata

34

28

Mayten, Maytenus boaria

Myrtle spurge, Euphorbia myrsinites

Ovate goatgrass, Aegilops geniculata

38

32

20

Pampas grass, Cortadeeria selloana

Ravenna grass, Saccharum ravennae

White bryony, Bryonia alba

28

30

36

Pinkish-Purple Flowers 40

Camelthorn, Alhagi maurorum 60

Crown vetch, Securigera varia 56

Hairy willowherb, Epilobium hirsutum

Himalayan balsam, Impatiens glandulifera

Iberian starthistle, Centaurea iberica

48

50

44

Italian thistle, Carduus pycnocephalus 40

Kudzu, Pueraria montana var. lobata 58

Plumeless thistle, Carduus acanthoides 40

Purple starthistle, Centaurea calcitrapa

Shiny geranium, Geranium lucidum

Slenderflower thistle, Carduus tenuiflorus

44

52

40
New Invaders of the Northwest 3

Squarrose knapweed, Centaurea virgata ssp. squarrosa 46

Wild four-o’clock, Mirabilis nyctaginea 54

White Flowers 62

Bridal veil broom, Retama monosperma 76

Bur chervil, Anthriscus caucalis 62

Common privet, Ligustrum vulgare 

Cutleaf teasel, Dipsacus laciniatus

78

66

English holly, Ilex aquifolium

Garlic mustard, Alliaria petiolata

82

68

Giant hogweed, Heracleum mantegazzianum 64

Goatsrue, Galega officinalis 74

Italian arum, Arum italicum 70

Mediterranean sage, Salvia aethiopis 72

Syrian beancaper, Zygophyllum fabago

Wild chervil, Anthriscus sylvestris

80

62

Yellow Flowers 84

Austrian yellow cress, Rorippa austriaca

Creeping yellow cress, Rorippa sylvestris

French broom, Genista monspessulana

84

84

104

Garden loosestrife, Lysimachia vulgaris 88

Oriental clematis, Clematis orientalis 102

Portuguese broom, Cytisus striatus 104

Sicilian starthistle, Centaurea sulphurea 90

Smooth distaff thistle, Carthamus creticus 92

Spanish broom, Spartium junceum 104

Spurge flax, Thymelaea passerina

Stinkwort, Dittrichia graveolens

96

94

Velvetleaf, Abutilon theophrasti 98

Woolly distaff thistle, Carthamus lanatus

Yellow archangel, Lamiastrum galeobdolon

Yellow clematis, Clematis tangutica

92

100

102

Yellowtuft, Alyssum corsicum & A. murale 86

Glossary 108

Selected References 112
About This Field Guide

4 New Invaders of the Northwest Introduction Invasive plants are a major concern worldwide. They displace native species, 

decrease forage and agricultural production, alter soil nutrients 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 (lag phase) and 

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

weed infestations is a costly endeavor; it is much more cost effective to allocate 

resources toward weed 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. The purpose of this guide is 

to help land users recognize new invasive plants, so they can be treated rapidly and 

eradicated rather than becoming large and expensive problems. 

This guide focuses on cool and temperate regions of northwestern North America, 

including portions of: Alaska, California, Colorado, Idaho, Montana, Oregon, 

Nevada, Utah, Washington, Wyoming, Alberta and British Columbia. The hot and 

arid regions of southwestern USA are the focus of the sister guide, New Invaders 

of the Southwest. There is some overlap between species and regions, especially in 

areas bordering our superficial boundary. 

The species in this guide were selected by:

1. Combining state and provincial noxious weed, watch, and new invader 

lists/alerts

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

California Invasive Plant Council and NatureServe 

3. Identifying those species not yet widespread throughout northwestern 

North America as first-round candidates

4. Combining the opinions of numerous state, provincial and regional 

weed 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. Select definitions of plant terms are included 

in the glossary. For more in-depth explanations of plant parts and plant life cycles, 

or for more help with plant identification, please see the suggested references listed 

at the end of this guide.
New Invaders of the Northwest 5

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 weeds. The USDA 

GRIN database (Germplasm Resources Information Network) was followed in 

this regard. Please note the scientific names for many species have changed since 

previous weed publications. 

Plant distribution data is presented in a map for each species. The sources used to 

compile current distribution information are included in a table below. Distribution 

information was also provided by individuals and recent weed alert reports. 

Weed Distribution Sources

Consortium of California Herbaria ucjeps.berkeley.edu/consortium/

Consortium of Pacific Northwest Herbaria www.pnwherbaria.org

EDDMapS eddmaps.org

Intermountain Region Herbarium Network intermountainbiota.org/portal/index.php

USDA-NRCS PLANTS Database plants.usda.gov/java/

Where information was available, counties and 

districts where the weed has been documented are 

represented by a solid gray fill. Some documented 

populations of weeds 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.

Weed spread is often rapid. Even if a weed 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 regions surrounding known infestations, as weed spread into nearby 

areas is likely. 

All states and provinces where a weed is listed as noxious are included in a special 

section. Some states and provinces have sub-levels for noxious weed designations. 

These are included in abbreviated form where applicable, and are explained in 

greater detail in a table on the following pages. 
6 New Invaders of the Northwest Introduction

State/Province Noxious Weed Classification 

Alaska (AK)

Prohibited 

Restricted 

Alberta (AB)

Prohibited 

Noxious

British Columbia (BC)

Provincial 

Regional 

California (CA) No sub-categories

Colorado (CO)

A 

B

C

Watch List

Idaho (ID)

EDRR 

Control 

Containment 

Montana (MT)

1a 

1b 

2a 

2b
New Invaders of the Northwest 7

Definition

Species prohibited in the state.

Species restricted from sale, with designated maximum allowances in seed mixes.

Species that are not established in Alberta, but have demonstrated detrimental effects in other 

provinces or states. Prevent establishment.

Species that are widely spread in various areas of the province, but can still pose a significant 

economic hardship once established. Controlling the spread of noxious weeds is critical to 

protecting areas that are not infested.

Species designated as noxious throughout the entire province.

Species designated as noxious in select regions within British Columbia.

Species in Colorado that are designated by the Commissioner for eradication.

Species for which the Commissioner, in consultation with the state noxious weed advisory 

committee, local governments, and other interested parties, develops and implements state noxious 

weed management plans designed to stop the continued spread of these species.

Species for which the Commissioner, in consultation with the state noxious weed advisory 

committee, local governments, and other interested parties, will develop and implement state 

noxious weed management plans designed to support the efforts of local governing bodies to 

facilitate more effective integrated weed management on private and public lands. The goal of such 

plans will not be to stop the continued spread of these species but to provide additional education, 

research, and biological control resources to jurisdictions that choose to require management of 

List C species.

Species that have been determined to pose a potential threat to the agricultural productivity 

and environmental values of the lands of the state. The Watch List is intended to serve advisory 

and educational purposes only. Its purpose is to encourage the identification and reporting of 

these species to the Commissioner in order to facilitate the collection of information to assist the 

Commissioner in determining which species should be designated as noxious weeds.

Species designated for immediate eradication if found.

Medium priority species designated for control where found.

Species already widespread; designated for containment of existing populations.

These weeds are not present in Montana. Management criteria will require eradication, and 

education and prevention efforts if detected.

These weeds have limited presence in Montana. Management criteria will require eradication or 

containment and education.

These weeds are common in isolated areas of Montana. Management criteria will require eradication 

or containment where less abundant. Management shall be prioritized by local weed districts.

These weeds are abundant in Montana and widespread in many countries. Management criteria will 

require eradication or containment where less abundant. Management shall be prioritized by local weed 

districts.
8 New Invaders of the Northwest Introduction

State/Province Noxious Weed Classification 

Montana (MT) cont. 3

Nevada (NV)

A 

B

C 

Oregon (OR)

A

B

Utah (UT)

A

B

C

Washington (WA)

A 

B

C 

Prohibited 

Wyoming (WY) No sub-categories
New Invaders of the Northwest 9

Definition

Regulated Plants (not Montana listed noxious weeds) have the potential to cause significant 

negative impacts. The plant may not be intentionally spread or sold other than as a contaminant in 

agricultural products. The state recommends research, education, and prevention to minimize the 

spread of the regulated plant.

Weeds not found or limited in distribution throughout the state; actively excluded from the state 

and actively eradicated wherever found.

Weeds established in scattered populations in some counties of the state; actively excluded where 

possible, actively eradicated from nursery stock dealer premises; control required by the state in 

areas where populations are not well established or previously unknown to occur.

Weeds currently established and generally widespread in many counties of the state; actively eradicated 

from nursery stock dealer premises; abatement at the discretion of the state quarantine officer.

Weeds of known economic importance which occur in the state in small enough infestations 

to make eradication or containment possible; or are not known to occur, but their presence in 

neighboring states make future occurrences in Oregon seem imminent. Recommended action: 

the species are prohibited from entering the state unless specifically exempted, and infestations are 

subject to eradication or intensive control when and where found.

Weeds of economic importance which are regionally abundant, but which may have limited 

distribution in some counties. Recommended action: the species are probited from entering 

the state unless specifically exempted, and infestations are assigned limited to intensive control 

at the state, county or regional level as determined on a site specific, case-by-case basis. Where 

implementation of a fully integrated statewide management plan is not feasible, biological control 

(when available) shall be the primary control method.

Species declared as “Early Detection and Rapid Response (EDRR)”. These are not native to the 

state of Utah, pose a serious threat to the state, have a relatively low population size within the state 

and are of the highest priority for control.

Species declared as "Control". These are not native to the state of Utah, pose a threat to the state, 

have a moderate population throughout the state, and generally are thought to be controllable in 

most areas.

Species declared as "Containment". These are not native to the state of Utah, pose a threat to the 

agricultural industry and agricultural products, are found extensively in the state, and are thought 

to be beyond control. Statewide efforts are generally towards containment of smaller infestations. 

Noxious weeds not native to the state that are of limited distribution or are unrecorded in the state 

and that pose a serious threat to the state. Eradication is required of all Class A noxious weeds.

Noxious weeds that are not native to the state and are designated for control in regions where they 

are not yet widespread. In regions where they are already abundant, control is decided at the local 

level, with containment as the primary goal.

Noxious weeds that are typically widespread in the state. Counties can provide education and have 

the option to require control if locally desired.

Species for which it is prohibited to transport, buy, sell, offer for sale, or distribute plants, plant 

parts, or seed mixes into or within the state.
10 New Invaders of the Northwest Introduction 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 weed authority immediately, 

and devise a treatment plan to eradicate the infestation as promptly as possible. 

Weed hotline numbers are listed below for those states and provinces providing 

this service. 

State/Province Weed Hotline

Alaska

Alberta

British Columbia

1-888-WEEDSBC (1-888-933-3722) for infestations in BC; or 

250-857-2472 for infestations found on Vancouver Island, the Gulf 

Islands or the Sunshine Coast

California 1-800-491-1899

Colorado

Idaho 1-866-IDWEEDS (1-866-439-3337)

Montana

Nevada

Oregon 1-866-INVADER (1-866-468-2337)

Utah

Washington 1-877-9-INFEST (1-877-946-3378)

Wyoming
New Invaders of the Northwest 11
Blueweed & Paterson’s curse

Echium vulgare L. & E. plantagineum L.

12 New Invaders of the Northwest Bluish PURPLE FLOWERS

Blueweed: a) plant (Robert Vidéki, Doronicum Kft.), b) stem, leaves, and flowers (Sue Winterowd, 

Stevens County NWCB), c) flowers (H. Zell) (a,b www.bugwood.org)

Paterson’s curse: d) plant (Frank Vincentz), e) rosette leaves (D Hochmayr), f) flowers and stem 

(Wolfgang Sauber) 

c

b

a

f

e

d
Family Boraginaceae

New Invaders of the Northwest 13

SYNONYMS: Blueweed (BW): viper’s bugloss; Paterson’s curse (PC): Salvation 

Jane, Riverina bluebell

ORIGIN: Europe (both species)

GROWTH TRAITS: Both species are herbaceous, growing 1-3’ tall (0.3-0.9 m) 

from a taproot. Stems are one to many and typically branched toward the top. 

At high densities, plants grow erect; with less vegetation, plants appear more 

sprawling. Leaves are oblong to linear, growing alternate and smaller further 

up the stem. Stems and leaves are covered in stiff hairs. Stem hairs are dark and 

swollen at their bases, giving stems a spotted appearance. Flowers are present 

from late spring to early fall in fiddleneck arrangements. Flowers are somewhat 

funnel-shaped with 5 fused purplish-blue petals and dark pink stamens; the top 

petals overhang the bottom. Flowers are subtended by bracts with multiple lobes 

and folds. Each flower produces four 1-seeded nutlets. BW is a biennial or shortlived perennial. 4 stamens protrude beyond the flower petals. PC is an annual or 

biennial. 2 stamens protrude beyond the flower petals. 

REPRODUCTION: Both species spread by seed. Seeds of BW are reportedly 

viable in the soil for up to three years; seeds of PC are viable for up to 10.

 

HABITAT: Both species capitalize on disturbed, sunny areas and can be found in 

pastures, abandoned fields, and roadsides.

LOOK-ALIKES: Both can be confused with other Echium and Anchusa species, 

all of which are exotic in North America. Several native species of Phacelia in 

the Hydrophyllaceae resemble these with their fiddleneck flower arrangements, 

protruding stamens, and similar flower color on some species. However, Phacelia

flowers are symmetrical while Echium flower lobes are unequal. The higher 

number of protruding stamens 

and the sharper, more intrusive 

hairs help differentiate these two 

species from each other. 

NOXIOUS WEED LISTINGS: BW: 

AB, BC (Regional), ID (Control), MT 

(2A), WA (B, Prohibited); PC: OR (A)

NOTES: Hairs of both species can pierce 

skin, causing irration. Blueweed Paterson’s curse
Pine echium

Echium pininana Webb & Berthel.

14 New Invaders of the Northwest Bluish PURPLE FLOWERS SYNONYMS: giant viper’s bugloss, tower of jewels

ORIGIN: Canary Islands

GROWTH TRAITS: Herbaceous biennial or triennial growing 61⁄2-13’ tall (2-4 

m) from a deep taproot. The plant typically remains as a tall rosette the first year, 

flowers the second or third year, and then dies. Rosette leaves are 10-20” long 

(25-50 cm), narrowly lance-shaped, deeply veined, and covered in fine, rough 

hairs. There is one main, unbranched, cylindrical flowering stem resembling a 

woody trunk 3.2-10’ tall (1-3 m). Stem leaves are similar to rosette leaves but are 

narrower and shorter (4-10” or 10-25 cm long). Flowers are present from late 

spring through summer in fiddleneck arrangements arising from stem leaf axils. 

Flowers are somewhat funnel-shaped with 5 fused purplish-blue petals and light 

pink stamens that extend beyond the petals. Flowers are subtended by lanceshaped bracts. Each flower produces 4 prickly, brown, 1-seeded nutlets.

REPRODUCTION: By seed. Seeds remain viable in the soil for many years.

 

Pine echium: a) flowering plant (©2001 CDFA), b) small infestation (Helena RG)

a b
Family Boraginaceae

New Invaders of the Northwest 15

HABITAT: Prefers sunny habitats with mesic to 

moist conditions. Thrives on steep and disturbed 

hillsides in coastal habitats. Limited by harsh 

winters and full shade.

LOOK-ALIKES: Leaves and flowers are similar 

to other exotic Echium species, including the two 

included in earlier pages of this guide. The massive 

cylindrical flowering stem of pine echium is 

unlike any other Echium species in western North 

America. 

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any western state or province.

NOTES: Though not listed as noxious anywhere, 

this is a species of concern in California where 

it has recently been documented as spreading. 

Regularly escapes cultivation.

Pine echium: c) leaves (James Steakley), d) flowers in fiddleneck arrangements and leaves (Frank 

Wouters), e) old flowering stem (Zoya Akulova)

Look-alike: Echium vulgare (Sue 

Winterowd, Stevens County 

NWCB)

c d e
Clary sage & Meadow clary

Salvia sclarea L. & S. pratensis L.

16 New Invaders of the Northwest Bluish PURPLE FLOWERS

Clary sage: a) plant, b) stem, stem leaves, and immature flowers (a,b Ettore Balocchi), c) flowers and 

bracts (Sue Winterowd, Stevens County NWCB)

Meadow clary: d) plant, e) basal leaves (d,e ©2014 Armadej Trnkoczy), f) flowers (H. Zell) 

f

e

d

c

b

a
Family Lamiaceae

New Invaders of the Northwest 17

SYNONYMS: Clary sage (CS): Europe sage; Meadow clary (MC): Meadow sage

ORIGIN: CS: Eurasia; MC: Europe

GROWTH TRAITS: Both species are herbaceous with square stems and opposite 

leaves. Leaves are wrinkled, toothed, and often covered in fuzz. Leaves are 

progressively smaller up the stem. Flowers are produced in summer in multiple 

whorls of 2-6 found at leaf nodes and in long spikes at stem tips. Flowers are 1” 

long (21⁄2 cm) and strongly 2-lipped with the lips widely separated. Each flower 

produces four 1-seeded nutlets. CS is a biennial to short-lived perennial growing 

3-5’ tall (90-150 cm) from a branched root system. Leaves may be doubly-toothed 

and are 6-12” long (15-30 cm). Basal leaves have petioles while stem leaves nearly 

clasp the stem. Upper lips of flowers are light purplish-blue while lower lips are 

typically white. Flowers are subtended by large, pinkish, petal-like bracts. MC

is a perennial growing 1-21⁄2’ tall (30-75 cm) from a fibrous root system. Leaves 

are egg-shaped, warty, have rounded teeth, and are 3-6” long (71⁄2-15 cm). Most 

leaves are basal. Flowers are purple to bluish and are subtended by small bracts.

REPRODUCTION: Both species spread by seed. Seeds of both are believed to 

remain viable in the soil for at least three years.

 

HABITAT: Both species capitalize on disturbance and can be found in pastures, 

meadows, hillsides, and roadsides, often in areas with at least partial sun.

LOOK-ALIKES: The opposite leaves, square stems, and 2-lipped flowers 

differentiate these plants from unrelated look-alikes. Within the family, there are 

many similar native and exotic species of Salvia and Mentha. The combination 

of widely separated flower lips, heavily flowered stems, and large basal leaves 

help differentiate these species from look-alikes. Plant size, bract size, and flower 

color help differentiate these 

species from each other.

NOXIOUS WEED LISTINGS:

Both species: WA (A, Prohibited)

NOTES: Both species are aromatic and 

used in herbal remedies. They are 

frequently cultivated but are escaping 

and becoming problematic.

Clary sage Meadow clary
Silverleaf nightshade

Solanum elaeagnifolium Cav.

18 New Invaders of the Northwest Bluish PURPLE FLOWERS SYNONYMS: white horsenettle, tomato weed

ORIGIN: Southwest United States, Mexico, South America

GROWTH TRAITS: Herbaceous perennial growing 1-3’ tall (30-90 cm) from a 

rhizomatous root system. The multiple stems are round with scattered, slender, 

and reddish spines. Leaves are alternate, lance-shaped with wavy margins, and 

1-4” long (21⁄2-10 cm). Leaves and stems are covered in short white hairs, giving 

the plant a silver-green or dusty appearance. The star-shaped flowers bloom 

through summer and are 3⁄4” (2 cm) in diameter. Flowers typically have 5 bluishpurple petals (occasionally white) and bright yellow stamens. Petals are fused 

at their bases. The fruits are clusters of round berries 0.4” (1 cm) in diameter. 

Berries are striped green when young but turn orange-yellow with maturity.

REPRODUCTION: By seed, rhizomes, and root fragments. Seeds remain viable 

in the soil for up to 10 years.

 

Silverleaf nightshade: a) plant (Florida Division of Plant Industry Archive, Florida Department of 

Agriculture and Consumer Services, www.bugwood.org), b) small infestation (Stan Shebs)

a b
Family Solanaceae

New Invaders of the Northwest 19

HABITAT: Occurs in semi-arid regions in cultivated 

fields, grasslands, pastures, and along roadsides. 

LOOK-ALIKES: The 5-petaled flowers with 

yellow stamens and berry fruits help differentiate 

this species from unrelated look-alikes. Several 

similar-looking species of native and exotic 

Solanum occur in North America, such as Carolina 

horsenettle (Solanum carolinense). Most of these 

can be differentiated by having more lobed leaves, 

different colored fruits, or white flowers with nonfused petals.

NOXIOUS WEED LISTINGS: CA, NV (B), OR 

(A), WA (A, Prohibited)

NOTES: Though native to portions of North 

America, it is regularly invasive inside and 

outside of its native range. All parts of the plant 

are toxic to livestock.

Silverleaf nightshade: c) leaves (Joseph M. DiTomaso, University of California - Davis), d) flower 

and reddish spines on stem (Pschemp), e) fruits (Florida Division of Plant Industry Archive, Florida 

Department of Agriculture and Consumer Services) (c,e www.bugwood.org)

Look-alike: Carolina horsenettle 

(James H. Miller & Ted Bodner 

Southern Weed Science Society)

c d e
Barbed & Ovate goatgrass

Aegilops triuncialis L. & A. geniculata Roth

20 New Invaders of the Northwest GREEN FLOWERS

Barbed goatgrass: a) infestation (Javier Martin), b) inflorescence (zoomed out and in, Matt Lavin, 

Bozeman, Montana, USA), c) spikelets (joints) (Steve Hurst, USDA NRCS PLANTS Database)

Ovate goatgrass: d) infestation, e) inflorescence (d,e Javier Martin), f) spikes with joints (Steve 

Hurst, USDA NRCS PLANTS Database)

f

e

d

c

b

a
Family Poaceae

New Invaders of the Northwest 21

SYNONYMS: Barbed goatgrass (BG): barb goat grass; Ovate goatgrass (OG):

Aegilops ovata auct., Triticum ovatum auct.

ORIGIN: Eurasia, northern Africa (both species)

GROWTH TRAITS: Both species are winter annuals growing from fibrous 

roots. Stems are erect and often branched and bent basally. Leaf blades are flat, 

0.8-0.12” wide (2-3 mm), and have finely hairy margins. The lower surface 

(and sometimes upper) is sparsely covered in fine hairs. Nodes are hairy. Ligules 

are very short and finely fringed. Inflorescences are spike-like with spikelets 

each forming “joints” at stem tips. All awns are stiff, sharp, and minutely 

barbed. Flowering occurs from May-July. BG plants are spreading or trailing in 

appearance and can be up to 11⁄2’ tall (45 cm). Stems are solid when young, but 

become hollow with age. Spikes are cylindric, 3⁄4-21⁄3” long (2-6 cm), and have 

2-6 spikelets. Immature spikes are often reddish or purple. Spikes break off as a 

whole unit at maturity, but eventually break apart into joints with sharp ends. 

OG plants are more tufted in appearance and grow to 10” tall (25 cm). Spikes 

are ovate-cylindric, 1⁄3-11⁄4” long (1-3 cm), and have 2-4 spikelets. Spikes break 

off as a whole and do not break into joints. Awns are more spreading.

REPRODUCTION: Both species spread only by seed, which are believed to stay 

viable in the soil for 3-5 years.

 

HABITAT: Both species prefer dry, disturbed fields, roadsides, and rangeland.

LOOK-ALIKES: The jointed inflorescences of goatgrasses are distinctive and 

unlikely to be confused with other weedy annual grasses. The widespread 

invasive jointed goatgrass (Aegilops cylindrica) is very similar to barbed goatgrass 

but grows slightly taller, has longer spikes, and has 3-12 spikelets. Separated 

joints have blunt ends. Stems 

of jointed goatgrass are always 

hollow, even when young.

NOXIOUS WEED LISTINGS:

Both species: CA, OR (A)

NOTES: Both species can hybridize with 

winter wheat, often leading to sterile 

seeds and unmarketable crops.

Barbed goatgrass Ovate goatgrass
Chinese silvergrass

Miscanthus sinensis Andersson

22 New Invaders of the Northwest GREEN FLOWERS SYNONYMS: eulalia, zebra grass

ORIGIN: Asia

GROWTH TRAITS: Perennial bunchgrass growing 5-10’ tall (11⁄2-3 m) from a 

rhizomatous root system. Leaves are upright to arching, up to 3’ long (0.9 m), 

and 0.4-0.8” wide (1-2 cm). Leaves have a whitish upper midrib, sharp tips, 

rough edges, and may be solid green or variegated with light, horizontal stripes. 

The inflorescence is fan-shaped, showy with silvery to pink florets, and occurs at 

stem tips in late summer. Inflorescences are typically up to 1’ long (30 cm). Each 

mature seed is rough with a twisted bristle tip that gives the overall inflorescence 

a cottony appearance.

REPRODUCTION: By seed, rhizomes, and root fragments. Rhizomatous 

spread is most common.

 

Chinese silvergrass: a) plant (James H. Miller, USDA Forest Service, www.bugwood.org), 

b) infestation (Jungle)

a b
Family Poaceae

New Invaders of the Northwest 23

HABITAT: Found in a variety of habitats but prefers 

full sun and moist, well-drained soil. It is intolerant 

of full shade as well as extreme heat and humidity. 

Frequently escapes cultivation, capitalizing on 

disturbance to become problematic along roadsides 

and forest edges.

LOOK-ALIKES: The bunched tussocks help 

differentiate Chinese silvergrass from the 

rhizomatous and linear-growing giant reed (Arundo 

donax) and common reed (Phragmites australis). 

Ravenna grass (Saccharum ravennae), jubata grass 

(Cortaderia jubata), and pampas grass (C. selloana) 

are all similar-looking bunchgrasses. Chinese silvergrass is typically shorter, has 

smaller leaves, and its plumes are more fan-like compared to jubata and pampas 

grass. Ravenna grass leaf and stem bases are 

densely hairy.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any western state or province.

NOTES: Listed as noxious and invasive in eastern 

North America. Tolerates cold climates well. Already 

present in California and recently found in shallow 

waters on the north shore of the Columbia River in 

Washington. The plant is highly flammable, creating 

a fire hazard.

Chinese silvergrass: c) leaf blades: normal (left, Britt Slattery, US Fish and Wildlife Service), variegated 

(right), d) flowering inflorescence, e) mature inflorescence (right c,d,e all Leslie J. Mehrhoff, University 

of Connecticut) (all www.bugwood.org)

Look-alike: jubata grass (Gordon 

Leppig & Andrea J. Pickart)

c d e
False brome

Brachypodium sylvaticum (Huds.) P. Beauv.

24 New Invaders of the Northwest GREEN FLOWERS SYNONYMS: slender false brome, wood false brome, Bromus sylvaticus (Huds.) 

Pollich, Festuca sylvatica Huds.

ORIGIN: Eurasia, northern Africa

GROWTH TRAITS: Perennial bunchgrass with individual clumps that merge to 

form one large mat up to 3’ tall (0.9 m). Leaves are drooping with bright green, 

flat blades up to 1⁄2” wide (1.2 cm). Leaves have a fringe of hairs surrounding 

margins, do not clasp the stem tightly, are hairy and open at their base, and have 

a fringed ligule at the point of attachment. Leaves are bright green all season or 

year long. Spikelets of flowers are on very short stalks, are droopy and hairy, and 

have straight awns 1⁄4-3⁄4” long (6-18 mm).

REPRODUCTION: By seed and can re-sprout from vegetative fragments; roots 

are not rhizomatous. Seeds reportedly remain viable for only one year.

 

False brome: a) plants (Cillas), b) infestation (Daderot)

a b
Family Poaceae

New Invaders of the Northwest 25

HABITAT: Found in forests and woodlands, but 

may grow in open areas such as roadsides and 

streambanks under a variety of environmental 

conditions. 

LOOK-ALIKES: Though grasses can be difficult 

to tell apart, this species is distinguished by being 

hairy on its leaf margins and lower stems, and 

its perennial bright green color. It is most easily 

confused with species of true brome (Bromus) but 

differs by having leaf sheaths open to the base and 

spikelets with no (or very short) stalks. Bromes 

have sheaths closed more than 1⁄4 of their length 

and spikelets on long stalks. 

NOXIOUS WEED LISTINGS: OR (B), WA 

(A, Prohibited)

NOTES: It appears populations at the leading edge 

of the expanding range undergo an establishment 

phase before they can contribute to the local 

invasion. This is perhaps because newly colonized 

populations are suffering from inbreeding depression.

False brome: c) leaf blade and margins, d) ligule and leaf attachment (©2014 Keir Morse), 

e) spikelets (c,e Alison Halpern, Washington State Noxious Weed Control Board)

Look-alike: true brome (Robert 

Mohlenbrock, USDA NRCS 

PLANTS Database)

c d e
Giant reed

Arundo donax L.

26 New Invaders of the Northwest GREEN FLOWERS SYNONYMS: elephant grass, Carrizo, Spanish/wild/giant cane, arundo

ORIGIN: Mediterranean region throughout the Middle East to India 

GROWTH TRAITS: Perennial grass reaching up to 26’ tall (8 m) and growing 

from an extensive rhizomatous root system. Each hollow stem resembles a corn 

stalk. First-year stems are unbranched, while second-year stems commonly 

branch and may only have leaves on the branches. Stems can root when they 

touch the ground. Leaves are long, flat, alternate, up to 11⁄2’ long (45 cm), and 

conspicuously in one plane. Leaf bases are heart-shaped, clasp the stem, and have 

small tufts of hair. Some cultivars have variegated coloration. Flowering occurs 

in late summer to early fall, though flowering is not frequently observed in the 

Pacific Northwest. Plumes are dense and can grow up to 3’ in length (0.9 m). 

REPRODUCTION: North American populations are not known to produce 

viable seeds. This species spreads predominantly by its rhizomatous root system 

and by producing roots when stems touch the ground.

 

Giant reed: a) plants (Shizhao), b) field planting (Jennifer Andreas, Washington State University Extension)

a b
Family Poaceae

New Invaders of the Northwest 27

HABITAT: Found in wetlands such as ditches, 

streambanks, and lake shores with fresh or 

moderately saline water. 

LOOK-ALIKES: Can be mistaken for native and 

exotic subspecies of common reed (Phragmites 

australis), a large grass growing in similar habitat 

and producing similar plumes. Common reed 

grows shorter (up to 20’ or 6 m), has smaller stems, 

has leaves that don’t clasp stems, and produces 

runners in addition to rhizomes. 

NOXIOUS WEED LISTINGS: CA, CO & 

NV (A), WA (Prohibited, except for variegated 

cultivars)

NOTES: This species is a favorable candidate 

for use as a renewable biofuel source in Europe 

and Africa because of its fast growth rate and its 

ability to grow in different soil types and climatic 

conditions. The same traits make it extremely 

invasive in parts of North America. In Oregon, the 

species is restricted; it can be grown for commercial 

purposes with a permit, but only variegated cultivars 

can be sold in nurseries. Washington has a similar 

permit process in place.

Giant reed: c) stem cross-section (Wendy DesCamp, Washington State Noxious Weed Control 

Board), d) leaf blade attachments with leaves all in one plane (Amy Ferriter, State of Idaho), 

e) flower plume (Chris Evans, Illinois Wildlife Action Plan)

Look-alike: common reed 

(Richard Old, www.xidservices.

com, www.bugwood.org)

c d e
Jubata & Pampas grass

Cortaderia jubata (Lemoine ex Carrière) Stapf & C. selloana (Schult. & Schult. f.) Asch. & Graebn.

28 New Invaders of the Northwest GREEN FLOWERS

Jubata grass: a) plant (Gordon Leppig & Andrea J. Pickart), b) leaf blade, c) inflorescence 

(b,c Forest & Kim Starr)

Pampas grass: d) plant (Wouter Hagens, taken in the Kijktuinen Nunspeet), e) variegated leaves of a 

cultivated plant (Kenpei), f) inflorescences (Kenneth M. Gale, www.bugwood.org)

f

e

d

c

b

a
Family Poaceae

New Invaders of the Northwest 29

SYNONYMS: Jubata grass (JG): Andean pampas grass, purple pampas grass, 

pampas grass; Pampas grass (PG): white pampas grass, Uruguayan pampas grass

ORIGIN: South America (both species)

GROWTH TRAITS: Both species are large, densely tufted perennial grasses 

growing from dense fibrous roots with shallow, short rhizomes. Leaves are very 

long and have sharply serrated margins. Ligules are dense rings of hairs 0.08-

0.12” long (2-3 mm). Dense flower plumes appear summer through fall and 

are 1-3’ long (30-90 cm). JG are all-female plants growing 6-23’ tall (1.8-7 m) 

with the stems at least 2 times longer than the spreading tussock. Leaves are 3-5’ 

long (0.9-1.5 m) and flat or slightly v-shaped in cross-section. Plumes are deep 

violet, turning pinkish then gold at maturity. Awns are very short. PG grows 

6-13’ tall (1.8-4 m). Plants are either all-female or hermaphroditic. Stems of 

hermaphroditic plants are 2 times longer than the tussock; female plant stems 

are equal to or slightly longer than the tussock. Leaves are up to 6’ long (1.8 m), 

v-shaped in cross-section, and with bristly, curled tips. Plumes are light pink to 

silver white; awns are long. Tussocks are more fountain-like than jubata grass.

REPRODUCTION: Both species spread by seed and fragmented tillers. Seeds 

are believed to remain viable in the soil for less than six months.

 

HABITAT: Both species prefer disturbed coastal sites such as bluffs, roadsides, steep 

cliffs, and riverbanks, but can also grow inland. PG can tolerate standing water.

LOOK-ALIKES: The bunched tussocks help differentiate jubata and pampas 

grass from the rhizomatous and linear-growing giant reed (Arundo donax) and 

common reed (Phragmites australis). Chinese silvergrass (Miscanthus sinensis) and 

Ravenna grass (Saccharum ravennae) are similar-looking bunchgrasses. Chinese 

silvergrass is shorter with smaller 

leaves and fan-like plumes. 

Ravenna grass leaf and stem bases 

are densely hairy.

NOXIOUS WEED LISTINGS: JG: 

CO (Watch List), OR (B); PG: No 

NW states or provinces

NOTES: Both species are escaped 

ornamentals. Jubata grass Pampas grass
Ravenna grass

Saccharum ravennae (L.) L.

30 New Invaders of the Northwest GREEN FLOWERS 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, Mediterranean

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

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

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

midvein on upper sides of blades, and can be 20-40” long (0.5-1 m) and 1⁄2” 

wide (1.2 cm). 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’ long (0.6 m), and bloom from July through October. 

Florets are covered in tufts of silky hairs, giving the inflorescence an overall fluffy 

appearance.

REPRODUCTION: By seed only. Seed viability is unknown.

Ravenna grass: a) plant (Jennifer Andreas, Washington State University Extension, b) infestation 

(The Nature Conservancy Archive, The Nature Conservancy, www.bugwood.org)

a b
Family Poaceae

New Invaders of the Northwest 31

HABITAT: Found in open, disturbed locations 

at both moist and dry sites including marshes, 

ditchbanks, seeps, floodplains, rocky hillsides, 

gravel roadsides, and escaped from yards. 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 similarlooking bunchgrasses, but Ravenna grass leaf and stem bases are densely hairy, 

its leaf margins are not as sharp, its leaf midveins are thick white on the upper 

sides of the blades, and its flowering stems can have red coloring.

NOXIOUS WEED LISTINGS: Not listed 

as noxious in any western state or province; 

proposed for listing in WA in 2015.

NOTES: Though not listed as noxious in the 

NW, its ecological impact ranking and potential 

for distribution are both high. Frequently used for 

soil erosion control and as an ornamental, but often 

escapes cultivation. Spreading rapidly in several parts 

of North America, and recently found in Wshington 

and Oregon.

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)

Look-alike: jubata grass (Gordon 

Leppig & Andrea J. Pickart)

c d e
Eggleaf & Myrtle spurge

Euphorbia oblongata Griseb. & E. myrsinites L.

32 New Invaders of the Northwest GREEN FLOWERS

Eggleaf spurge: a) plants (Marty Hudson, Klickitat County NWCB), b) leaves, bracts, and flowers 

(Dominicus Johannes Bergsma), c) stem, bracts, flower, and fruit (San Juan County NWCB)

Myrtle spurge: d) plant/small infestation (Jebulon), e) leaves, bracts, and flowers from above 

(D Hochmayr), f) and from the side (Steve Dewey, Utah State University, www.bugwood.org) 

a b

f

e

d

c

b
Family Euphorbiaceae

New Invaders of the Northwest 33

SYNONYMS: Eggleaf spurge (ES): oblong spurge; Myrtle spurge (MS): blue 

spurge, creeping spurge, donkey tail

ORIGIN: Eurasia (both species)

GROWTH TRAITS: Both species are herbaceous and perennial, exuding a 

white latex sap when torn. Flowers are inconspicuous, yellow, and surrounded 

by yellowish-green, showy bracts. Seeds are brown, round, smooth, and can be 

propelled several feet from the plant upon drying. ES is erect, reaching heights 

of 3’ (0.9 m) from a woody, branched taproot. It has alternate, lance-shaped, 

green leaves up to 21⁄2” long (6 cm) with very fine teeth along all margins. Stems 

are often densely hairy. Flowering occurs summer through fall. MS is a spreading 

plant reaching a height of 8”(15 cm) from a taproot, though its leaning stems are 

up to 16” (40 cm) long. Leaves are succulent, gray green, ovate with sharp tips, 

and arranged spirally along the succulent stem. Flowering occurs throughout 

spring.

REPRODUCTION: Both species spread by seed, root fragments, and root crown 

budding. Seeds are typically short-lived but can be viable for up to eight years.

 

HABITAT: Both species capitalize on disturbance and can be found from moist 

meadows to dry hillsides.

LOOK-ALIKES: Many species of Euphorbia resemble eggleaf and myrtle spurge. 

The majority of those which occur in the Northwest are exotic. These species 

can be differentiated by comparing the toothed leaf margins of eggleaf spurge 

and succulent leaves of myrtle spurge to features of other exotic and native 

Euphorbia, which often lack these traits. Carnation spurge is similar to eggleaf 

spurge, but has hairless stems. Pre-flowering myrtle spurge can resemble preflowering Dalmatian toadflax 

shoots, but myrtle spurge has a 

leaning habit and latex sap.

NOXIOUS WEED LISTINGS:

ES: CA, OR (A), WA (A, Prohibited); 

MS: CO (A), OR & WA (B)

NOTES: Both species are escaped 

ornamentals. The latex sap is toxic and 

should be handled with care. Eggleaf spurge Myrtle spurge
Japanese chaff flower

Achyranthes japonica (Miq.) Nakai

34 New Invaders of the Northwest GREEN FLOWERS SYNONYMS: Not applicable

ORIGIN: eastern Asia

GROWTH TRAITS: Herbaceous, upright perennial typically growing 20-40” 

tall (1⁄2-1 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 red at their base. 

Leaves are opposite, elliptic, and have deep veins and smooth margins. Leaves 

are 4-8” long (10-20 cm), gradually becoming smaller up the stem. Leaves and 

stems are slightly hairy. Flowers occur in tight clusters on spikes at branch and 

stem tips from late summer to early fall. Flowers are tiny with no petals and 5 

green stamens. 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 that aid the fruit in 

attaching to clothes or fur. 

Japanese chaff flower: a) plant, b) infestation (a,b both Chris Evans, Illinois Wildlife Action Plan, 

www.bugwood.org)

a b
Family Amaranthaceae

New Invaders of the Northwest 35

REPRODUCTION: By seed. Seeds have very high 

viability rates, though it is unknown for how long 

seeds remain viable in the soil.

 

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 at the 

edges of fields. 

LOOK-ALIKES: Related pigweed species 

(Amaranthus) have similar flowers and reddish 

stem bases, however they have alternate leaves. The 

native American lopseed (Phryma leptostachya) has 

opposite leaves and similar fruit, however its leaves 

are toothed and it has pinkish-white petals.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any western state or province.

NOTES: While not currently established in the 

Northwest, nor listed as noxious anywhere, a recent 

APHIS weed risk assessment predicted the species 

would be able to grow in areas of the Pacific Northwest. 

It is established in the Midwestern US and causes 

extensive ecological damage throughout its weedy 

range.

Japanese chaff flower: c) leaves, d) flowers, e) fruit and hairy stem (c-e all Chris Evans, Illinois 

Wildlife Action Plan, www.bugwood.org)

Look-alike: American lopseed 

(Karan A. Rawlins, University 

of Georgia, www.bugwood.org)

c d e
White bryony

Bryonia alba L.

36 New Invaders of the Northwest GREEN FLOWERS SYNONYMS: white bryonia, wild hops, devil’s turnip, western kudzu

ORIGIN: Eurasia

GROWTH TRAITS: Herbaceous, perennial vine growing from a tuberous 

yellow root. Vines re-sprout from the root each year, growing up to 30’ (9 

m) during the growing season. Vines smother trees, shrubs, utility poles, etc. 

with the aid of tendrils, and form a mat on the ground when growing without 

supporting vegetation or structures. Leaves are alternate, distinctly 3 or 5-lobed, 

toothed, green, and have small white glands on both upper and lower surfaces. 

Flowers have 5 greenish-white petals with strong green venation; separate male 

and female flowers appear on the same plant. Flowers are up to 1⁄2” across (11⁄4 

cm) and appear in clusters from early spring through early fall. Fruits are clusters 

of berries that are green at first but turn black with maturity. 

White bryony: a) vines, b) infestation spreading over existing vegetation (Robin Kusske, Franklin 

County NWCB)

a b
Family Cucurbitaceae

New Invaders of the Northwest 37

REPRODUCTION: By seed. Seeds can remain 

viable in the soil for many years.

 

HABITAT: As birds are the most common dispersal 

agent, the plant is prevalent at bird feeding and 

nesting sites including riparian buffers, windrows, 

parks, fences, and wildlife plantings. 

LOOK-ALIKES: Several wild cucumber species 

native to North America resemble the leaf shape 

and climbing habit of white bryony. Echinocystis 

lobata is an annual vine with long clusters of male 

flowers with 6 narrow petals each. Marah spp. 

(manroot) are perennial and have flowers similar 

to but more white than white bryony. The fruits of 

both E. lobata and Marah spp. resemble small, 

spiny cucumbers.

NOXIOUS WEED LISTINGS: CO (Watch 

list), ID (Containment), OR (A), WA (B)

NOTES: All parts of the plant are poisonous to humans 

and most livestock. Crushed berries give off a foul odor.

White bryony: c) leaf, d) flower cluster (c,d Robin Kusske, Franklin County NWCB), e) mature 

fruits (Jan Samanek, State Phytosanitary Administration) (c-e www.bugwood.org)

Look-alike: wild cucumber 

(Barbara Tokarska-Guzik, 

University of Silesia, www.

bugwood.org)

c d e
Mayten

Maytenus boaria Molina

38 New Invaders of the Northwest GREEN FLOWERS SYNONYMS: Chilean mayten, green showers

ORIGIN: South America

GROWTH TRAITS: Evergreen tree typically growing 20-50’ tall (6-15 m) from 

an extensive root system that regularly sends up suckers near the parent tree. 

The tree has a rounded crown with weeping, pendulous branches that are green 

when young but age gray-brown. The straight trunk has rough bark and is up 

to 30” in diameter (76 cm). Leaves are thick, elliptic, 1-2” long (21⁄2-5 cm), and 

light green with toothed margins. Leaves are alternate and held perpendicular to 

the branch. Flowers appear in spring and are either male (brownish-yellow) or 

female (5 green petals with light purple lines). Both flower types are small and 

appear on the same tree. The fruit is a yellow capsule containing 1-2 seeds and is 

covered by a red-colored membrane.

REPRODUCTION: By seed and suckering from roots. It is unknown how long 

seeds may remain viable in the soil.

 

Mayten: a) tree (jpsti_777), b) numerous suckers sprouting around large tree (Jon Sullivan)

a b
Family Celastraceae

New Invaders of the Northwest 39

HABITAT: Found in full sun and moist, well-drained 

soil. It is intolerant of full shade and harsh winters. 

Frequently escapes cultivation, capitalizing on 

disturbance to become problematic along hillsides 

and in pastures.

LOOK-ALIKES: Weeping willow (Salix babylonica 

and related hybrids) resembles mayten with its 

weeping, pendulous branches and rough bark. 

However, weeping willow is deciduous with golden 

branches while mayten is evergreen with green or 

brown branches. Weeping willow leaves are half as 

wide as mayten and are not perpendicular to the 

branches. Finally, the flowers of weeping willow are tiny and occur in small, tight 

clusters, and its male and female flowers occur on separate trees.

NOXIOUS WEED LISTINGS: Not listed as noxious in any western state or 

province.

NOTES: Though not listed as noxious anywhere, 

this is a species of concern in California where 

it has escaped cultivation and has recently been 

documented spreading.

Mayten: c) leaves (Jon Sullivan), d) female flowers (Pato Novoa), e) fruits (Inao Vásquez)

Look-alike: weeping willow 

(Antilived)

c d e
Carduus thistles

40 New Invaders of the Northwest PINKISH PURPLE FLOWERS Trait

Italian

Carduus pycnocephalus

Plumeless

Carduus acanthoides

Slenderflower

Carduus tenuiflorus

Life

History

Annual or Biennial Annual or Biennial Annual or Biennial

Preferred

Habitat

Disturbed, open; 

High pH soil; Dry

Disturbed; Welldrained soil; MesicOpen areas; Fertile soil; 

Dry

Avg Height 4’ (1.2 m) 31⁄2’ (1.1 m) 3.2’ (1 m)

Basal

Leaves

≤5” long (13 cm); 

Deeply lobed; Short 

matted hairs on 

undersides; Spines on 

lobe tips and margins

≤8” long (20 cm);

Deeply lobed to 

midvein; Hairy 

underside; 1-3 spines 

on each lobe margin

≤5” long (13 cm); 

Deeply lobed; Short 

matted hairs on 

undersides; Spines on 

lobe tips and margins

Stems

Slightly winged and 

spiny along entire 

length

Leaf-like spines 

covering stems entire 

length

Triangular stem wings 

tipped with spines along 

entire length

Capitulum

Diameter ≤ 1” (21⁄2 cm) ≤ 1” (21⁄2 cm) <1” (<21⁄2 cm)

Bracts

Triangular; Have stiff, 

forward-pointing 

hairs; Cobwebby

Spiny; Needle-like Spiny; Triangular but 

narrow

Italian thistle: a) plant (Eric Coombs, Oregon Department of Agriculture), b) stem (©1995 Saint 

Mary’s College of California), c) flower heads (Mary Ellen Harte) (a,c www.bugwood.org)

c

b

a
Family Asteraceae

New Invaders of the Northwest 41

Plumeless thistle: d) plants, e) stem (Richard Old, www.xidservices.com), f) flower heads (d,f Becca 

Van Kampen, MIA Consulting)

Slenderflower thistle: g) plants (Javier Martin), h) leaf base and stem (Thurston County (WA) 

Noxious Weed Board), i) flower heads (Washington State Noxious Weed Control Board) 

i

h

g

f

e

d
Carduus thistles (continued)

42 New Invaders of the Northwest PINKISH PURPLE FLOWERS NAMES: Italian thistle, Carduus pycnocephalus L. (IT)

 Plumeless thistle, Carduus acanthoides L. (PT)

 Slenderflower thistle, Carduus tenuiflorus Curtis (ST)

SYNONYMS: IT: Italian plumed thistle; PT: bristly thistle, spiny plumeless 

thistle; ST: winged plumeless thistle

ORIGIN: Europe, Asia, northern Africa (all species)

GROWTH TRAITS:

Italian thistle (IT): Herbaceous winter annual or biennial often growing to 4’ tall 

(1.2 m) from a long taproot. Leaves (≤5” or 13 cm long) are lance-shaped, green 

and hairless above, hairy below, and have spines on lobe tips. Stem leaves grow 

alternately and lightly clasp the winged stem, which is spiny along its entire 

length. Flower heads are thimble-sized (up to 1” or 21⁄2 cm in diameter) in 

clusters of 2 to 5 at branch tips. Bracts are triangular and have tiny, firm, forwardpointing hairs along the midrib. Bracts are cobwebby at the base. Flowers are 

pink to purple and appear from April to July.

Plumeless thistle (PT): Herbaceous winter annual or biennial growing 3-4’ tall 

(0.9-1.2 m) from a fleshy taproot that is hollow near the crown. Leaves (≤8” or 

20 cm long) are hairy on the undersides, narrow, deeply lobed (almost to the 

midrib), finely divided, and have spines along margins. Basal leaves on some 

plants may have white margins. Stem leaves grow alternately and lightly clasp 

the stem. Flower heads are up to 1” (21⁄2 cm) in diameter and are either solitary 

or form small clusters of up to 5 heads at the ends of stems and branches. Bracts 

are needle-like and tipped with sharp spines. Flowers are pink to purple and 

appear from June to October. 

Slenderflower thistle (ST): Herbaceous winter annual or biennial growing 3-4’ tall 

(0.9-1.2 m) from a shallow and slender taproot. Stems are winged and spiny 

along their entire length. The alternate leaves are lance-shaped and gray-green 

with light-colored veins and spiny margins. They are hairless and spiny above, 

hairy below. Flower heads are less than 1” (21⁄2 cm) in diameter, growing in 

clusters of 5 to 20 at the ends of stems. Bracts are triangular, tipped with spines, 

and not hairy. Flowers vary from pink to purple and bloom from April to June.

REPRODUCTION: All three species reproduce by seed only. Seeds of many 

Carduus species may remain viable in the soil for up to 10 years, though most 

germinate within three.

 
Family Asteraceae

New Invaders of the Northwest 43

HABITAT: All three species capitalize on disturbance for establishment and can be 

found in open areas such as pastures, rangelands, and rights-of-way. IT prefers 

dry conditions and high pH soil. PT prefers moist conditions with well-drained 

soil. ST prefers dry conditions with fertile soil.

LOOK-ALIKES: Over 80 native thistle species 

occur in North America and could be confused for 

all three Carduus species described on these pages. 

Native thistles never have spines along their entire 

stems as do Italian, plumeless and slenderflower 

thistles. To differentiate these three species from 

the more than 20 exotic thistle species established 

in North America, these three have the following 

combination: spines along their entire stem length, 

small flower heads (≤ 1” or 21⁄2 cm), and narrow 

triangular bracts. To differentiate these three species 

from each other, refer to the comparison table three 

pages previous. IT and ST resemble each other the 

most but can be differentiated by the presence of hairs or cobwebs on bracts.

NOXIOUS WEED LISTINGS:IT & ST: CA, OR (B), WA (A, Prohibited); PT: 

AB (Prohibited), BC (Regional), CA & CO (B), OR (A), WA (B, Prohibited), 

ID (Containment), WY

NOTES: PT produces one type of seed which has a pappus of small white bristles. 

Both IT and ST produce two types of seeds. Those in the center of the capitulum 

are cream-colored and have a plume of whitish barbed hairs that aid in wind 

dispersal. Seeds from the outer portions of the capitulum are smooth, dark, and 

lack a pappus. These have no obvious means of dispersal and are often dormant. 

Look-alike: native thistle (Rich 

Hansen, USDA APHIS PPQ)

Italian thistle Plumeless thistle Slenderflower thistle
Iberian & Purple starthistle

Centaurea iberica Trevir. ex Spreng. & C. calcitrapa L.

44 New Invaders of the Northwest PINKISH PURPLE FLOWERS

Iberian starthistle: a) plant with flower heads (Eitan f), b) leaf, c) seeds (b,c ©2001 CDFA)

Purple starthistle: d) plant with flower heads (Xemenendura), e) leaf and stem (Solanum), f) seeds 

(D. Walters and C. Southwick, USDA, www.bugwood.org) 

f

e

d

c

b

a
Family Asteraceae

New Invaders of the Northwest 45

SYNONYMS: Iberian starthistle (IS): Iberian knapweed; Purple starthistle (PS):

red starthistle

ORIGIN: southern Europe, Middle East (both species)

GROWTH TRAITS: Both species are herbaceous annuals to short-lived 

perennials typically growing 2-4’ tall (0.6-1.2 m) from a stout taproot. Plants 

often grow as rosettes with spiny centers the first year and then flower the second 

year. Stems and leaves are covered with fine hairs. Lower and basal leaves are 

divided or deeply lobed while upper leaves are not. All leaves often have a light 

green or gray-green appearance. Flowering occurs from July to October when 

numerous lavender to purple flower heads (3⁄4-1” or 2-21⁄2 cm in diameter) 

develop at stem tips. Floral bracts are tipped with 1” long (21⁄2 cm) straw-colored 

spines. The two species can be differentiated by their seeds. IS produces plumed 

seeds while seeds of PS are plumeless. 

REPRODUCTION: Both species spread only by seed. Most seed germinates 

the first year, but buried seeds of both species can remain viable in the soil for 

approximately three years.

 

HABITAT: Both species are found in dry and/or disturbed areas, especially along 

roadways and in dry, grazed rangeland. 

LOOK-ALIKES: Both species resemble other members of the Centaurea genus. 

Starthistles can be distinguished by the very long, straw-colored spines extending 

from bract tips. Yellow starthistle differs from these two species with its yellow 

flower head color and winged stems. 

NOXIOUS WEED LISTINGS: IS: CA, NV & OR (A); PS: CA, NV & OR 

(A), WA (A, Prohibited)

NOTES: Unpalatable to livestock; 

may cause the fatal “chewing 

disease” in horses.

Iberian starthistle Purple starthistle
Squarrose knapweed

Centaurea virgata Lam. ssp. squarrosa (Boiss.) Gugler

46 New Invaders of the Northwest PINKISH PURPLE FLOWERS SYNONYMS: Centaurea squarrosa Willd., C. virgata auct. Amer., C. triumfettii All. 

ORIGIN: Eurasia

GROWTH TRAITS: Herbaceous perennial growing 11⁄2-3’ tall (0.45-0.90 m) 

from a stout taproot. The many-branched plant has leaves that are gray-green, 

alternate, and deeply dissected. Stem leaves have fewer to no lobes further up 

the plant. Flower heads develop singly or in pairs at the tips of branches. Flower 

heads are ≤1⁄4” (6 mm) in diameter so are much more slender than most other 

knapweeds. Florets are pink or rose-colored. Bracts have recurved tips, with the 

terminal spine longer than the lateral spines on each bract. Flowering occurs in 

early to mid-summer. Seeds are golden to dark brown and have a white pappus.

REPRODUCTION: By seed. Seeds may remain viable in the soil for many years.

 

HABITAT: Found in dry, open, and disturbed sites such as rangelands, roadsides, 

and grasslands.

Squarrose knapweed: a) bushy plant, b) infestation (a,b Steve Dewey, Utah State University, www.

bugwood.org)

a b
Family Asteraceae

New Invaders of the Northwest 47

LOOK-ALIKES: Numerous Centaurea resemble 

this species; most are themselves exotic and 

invasive. Diffuse knapweed (C. diffusa) is the most 

similar weedy knapweed, and can be differentiated 

by having a thicker flower head with non-curved 

bracts. The florets of diffuse knapweed are typically 

white but may occasionally be pink, similar to 

squarrose knapweed. Several native plants are 

similar to squarrose knapweed during various 

stages, especially asters when in bud. Asters 

(spanning several genera) can be differentiated by 

their undivided leaves and smooth, non-toothed 

bracts. Asters also have two types of flowers in 

one flower head, somewhat resembling daisies or 

sunflowers. 

NOXIOUS WEED LISTINGS:

AB (Prohibited), CA, CO NV & OR (A), ID 

(EDRR), UT (B)

NOTES: Individual seed heads fall or detach as a 

unit and can attach to fur and clothing, which aids 

in seed dispersal.

Squarrose knapweed: c) rosette, d) leaves (Joseph M. DiTomaso, University of California - Davis), 

e) flower heads (c,e Steve Dewey, Utah State University) (c-e www.bugwood.org)

Look-alike: diffuse knapweed 

(Jennifer Andreas, Washington 

State University Extension)

c d e
Hairy willowherb

Epilobium hirsutum L.

48 New Invaders of the Northwest PINKISH PURPLE FLOWERS SYNONYMS: great willowherb, great hairy willowherb, codlins and cream

ORIGIN: Africa, Asia, Europe

GROWTH TRAITS: Upright, herbaceous perennial growing up to 61⁄2’ tall 

(2 m) from extensive rhizomes. Stems are robust and multi-branched. Leaves 

are opposite, attached without stalks, lance-shaped, and have toothed margins. 

Leaves can be 1-5” long (21⁄2-121⁄2 cm). Stems and leaves are covered in fine 

hairs. Flowers have 4 pinkish-purple, notched petals with white centers. Flowers 

can be up to 1” in diameter (21⁄2 cm) and appear from summer through early 

fall. Sepals are green. Fruits are capsules that are very thin and long (2-3” or 

5-71⁄2 cm) and open at maturity to release numerous seeds. Each seed is small, 

oblong, flattened, and has a tuft of long whitish hairs. 

REPRODUCTION: By seed and rhizomes. Seeds may remain viable in the soil 

for three or more years. 

 

Hairy willowherb: a) young plants (André Karwath), b) infestation (Wendy DesCamp, Washington 

State Noxious Weed Control Board)

a b
Family Onagraceae

New Invaders of the Northwest 49

HABITAT: Typically found in moist areas, including 

ditches, wetlands, meadows, and moist pastures. 

Prefers open, sunny conditions but can tolerate 

semi-shade. 

LOOK-ALIKES: Several other species of Epilobium 

are native to North America and closely resemble 

hairy willowherb. Most look-alikes have either 

smaller flowers, different leaf shapes, occur in 

different habitats, or are annuals with different 

root systems. Fireweed is a very similar, related 

species whose name was recently changed from E. 

angustifolium to Chamaenerion angustifolium. It can be differentiated from hairy 

willowherb by its spiral leaf arrangement, greater numbers of flowers occurring 

at stem tips, petals that overlap less than hairy willowherb, and by its pink 

sepals. The exotic Himalayan balsam (Impatiens glandulifera) is also similar, but 

its flowers occur in larger clusters, its petals are 

fused and somewhat tubular, and its stems are 

purple-tinged and hollow.

NOXIOUS WEED LISTINGS: CO (Watch 

List), WA (B, Prohibited)

NOTES: Often found growing with purple loosestrife, 

which it can out-compete in the fall. The opposite is 

true in spring.

Hairy willowherb: c) leaves, d) flowers, e) mature and splitting fruit (c-e Wendy DesCamp, 

Washington State Noxious Weed Control Board)

Look-alike: fireweed (Kallerna)

c d e
Himalayan balsam

Impatiens glandulifera Royle

50 New Invaders of the Northwest PINKISH PURPLE FLOWERS SYNONYMS: ornamental jewelweed, policeman’s helmet, Impatiens roylei Walp.

ORIGIN: Asia (Himalayas)

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

shallow, fibrous root system. Stems are smooth, hairless, hollow, and often have 

a purplish tinge. Leaves are elliptic, 2-9” long (5-23 cm), 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 ~11⁄3” 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 

teardrop-shaped, 3⁄4-11⁄4” long (2-3 cm), and green. Seed pods explode when 

disturbed, scattering the small brown seeds up to 23’ (7 m).

REPRODUCTION: By seed. Seeds may remain viable in the soil for up to 18 

months. 

 

Himalayan balsam: a) plant (Udo Schmidt), b) roadside infestation (Wassily)

a b
Family Balsaminaceae

New Invaders of the Northwest 51

HABITAT: Largely found in moist areas including 

woodlands, forest clearings, streambanks, meadows, 

and roadsides where water collects. 

LOOK-ALIKES: Many native and exotic species 

within the Impatiens genus resemble Himalayan 

balsam. Most look-alike relatives have smaller leaves 

(frequently alternate) and/or flowers with different 

colors. 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. Hairy willowherb (Epilobium hirsutum) is also similar, 

but its flowers are more solitary and have 4 notched, unfused, and overlapping 

petals. 

NOXIOUS WEED LISTINGS:

AB (Prohibited), ID (EDRR), OR (B), WA 

(B, Prohibited)

NOTES: Seeds require a cold treatment in order to 

germinate; some can germinate under water. Sold 

as an ornamental that frequently escapes cultivation. 

Himalayan balsam: c) leaves and stem (Markus Nolf), d) flower and fruit (Barbara Tokarska, Guzik 

University of Silesia, www.bugwood.org), e) 2 mature and 1 exploded seed pod (Rasbak)

Look-alike: fireweed (Kallerna)

c d e
Shiny geranium

Geranium lucidum L.

52 New Invaders of the Northwest PINKISH PURPLE FLOWERS SYNONYMS: shiny crane’s-bill

ORIGIN: Europe, Asia, northern Africa

GROWTH TRAITS: Herbaceous erect winter annual or biennial growing 2-18” 

tall (5-45 cm) from a weak central root. Stems are hairless and often reddishcolored. The alternate leaves are shiny and rounded, divided into 5-7 lobes with 

lobed edges, and sparsely covered with stiff hairs. Flowers appear in clumps of 2 

throughout spring and early summer, or at other times of the year depending on 

the climate. Flowers have 5 pink petals; each petal is less than 0.4” long (1 cm). 

Sepals are fused, hairless, and strongly keeled with transverse wrinkles, appearing 

like ridges with bristled tips. The fruit has a beak-like projection that coils back 

forcefully at maturity to project seeds outwards, typical of most species in the 

family. Seeds are small and oval, reddish, and with a black projection. All green 

parts of the plant are tinged red either with age or with differing light conditions.

Shiny geranium: a) plant, b) infestation (a,b Alison Halpern, Washington State Noxious Weed 

Control Board)

a b
Family Geraniaceae

New Invaders of the Northwest 53

REPRODUCTION: By seed. Seeds may remain 

viable in the soil for many years.

 

HABITAT: Found in moist, disturbed areas such as 

roadsides and ditches at low elevations as well as in 

shady woodlands.

LOOK-ALIKES: Resembles many species in the 

Geraniaceae family with its pinkish-purple flowers 

and long crane’s-bill fruit. The strongly keeled 

sepals help differentiate shiny geranium. Dovefoot 

geranium (Geranium molle) has fuzzy sepals and 

similarly-shaped but hairier leaves with prominent 

veins in both leaves and flowers. Dovefoot flowers 

are deeply lobed, so the 5 petals appear almost as 10. Other related Geraniaceae 

have larger, veined flowers and leaves that are either much pointier or are so 

deeply lobed that they appear divided.

NOXIOUS WEED LISTINGS: OR (B), WA 

(A, Prohibited)

NOTES: Seeds require a period of desiccation to 

break dormancy.

Shiny geranium: c) leaf (Alison Halpern, Washington State Noxious Weed Control Board), d) flower, 

e) fruit at full length (left) and zoomed in (right) to show the sepal ridges (d-e Ben Legler)

Look-alike: dovefoot geranium 

(Jennifer Andreas, Washington 

State University Extension)

c d e
Wild four-o’clock

Mirabilis nyctaginea (Michx.) MacMill.

54 New Invaders of the Northwest PINKISH PURPLE FLOWERS SYNONYMS: heartleaf four o’clock, heartleaf umbrella wort, Allionia nyctaginea 

Michx.

ORIGIN: North America (east of the Rocky Mountains)

GROWTH TRAITS: Herbaceous perennial growing up to 4’ tall (1.2 m) from a 

fleshy, black taproot. Stems are smooth with a waxy bloom and produce opposite 

branches. Leaves are opposite, up to 4” long (10 cm), waxy, and either ovate or 

heart-shaped. Flowers occur in clusters of 3-5 near branch tips. Each flower has 

no petals but 5 notched, pink to lavender sepals and yellow stamens. Flowers are 

0.4” (1 cm) in diameter and are subtended by a whorl of large, papery bracts. 

Brown fruits have 5 prominent veins, are warty, and <1⁄4” long (3-6 mm). The 

seeds are hard, oblong nutlets that are produced from July to September.

REPRODUCTION: By seed. Seeds may remain viable in the soil for a few years.

 

Wild four-o’clock: a) plant (Jennifer Andreas, Washington State University Extension), 

b) infestation (Laura Blanchard)

a b
Family Nyctaginaceae

New Invaders of the Northwest 55

HABITAT: Found in a wide range of conditions 

including waste areas, roadsides, railroad lines, 

orchards, perennial crop fields, dry meadows, 

riparian areas, and rangelands. Most often (though 

not always) found in well-drained soil.

LOOK-ALIKES: The opposite and ovate leaves, 

lack of petals, and short-lived pink sepals help 

differentiate this species from unrelated look-alikes. 

Several native four-o’clock species occur in North 

America, including the threatened and endangered 

Macfarlane’s four-o’clock (Mirabilis macfarlanei). 

Many look very similar to wild four-o’clock so 

care should be taken in identification. The related 

species often have subtle differences in the shape, 

size, texture and color of leaves and flowers.

NOXIOUS WEED LISTINGS: WA (A, 

Prohibited)

NOTES: Though native to portions of North 

America, it is regularly invasive inside and outside of 

its native range. The name “four-o’clock” refers to the 

flowers opening late in the day and withering early the 

next morning.

Wild four-o’clock: c) leaves, d) flower and bracts surrounding fruits (c,d Jennifer Andreas, 

Washington State University Extension), e) fruits surrounded by bracts (Catherine Herms, The 

Ohio State University, www.bugwood.org)

Look-alike: Macfarlane’s fouro’clock (Thomas Kaye, Oregon 

Department of Agriculture)

c d e
Crown vetch

Securigera varia (L.) Lassen

56 New Invaders of the Northwest PINKISH PURPLE FLOWERS SYNONYMS: Purple crown vetch, common crown-vetch, Coronilla varia L.

ORIGIN: Eurasia

GROWTH TRAITS: Perennial, herbaceous forb often behaving as a vine that 

forms thick mats over open ground or competing vegetation. Plants typically 

grow 1’ tall (0.3 m) from a fleshy, rhizomatous root system; however, flowering 

plants may be up to 3’ tall (0.9 m). Leaves are alternate, 2-6” long (5-15 cm), 

and divided into 3-12 pairs of leaflets and a single terminal leaflet. Leaflets are 

0.4-1” long (1-21⁄2 cm). Flowers appear in leaf axils from late spring through 

early fall in a spreading umbel that resembles a crown with 6-25 flowers. Flowers 

are pale pink to deeper rose, pea-like (having a banner, wing and keel, typical of 

the pea family), and are 1⁄3-1⁄2” long (9-12 mm) with 10 stamens. Fruits are pods 

up to 2” long (5 cm) containing 3-7 rod-shaped seeds.

REPRODUCTION: By seed and the rhizomatous root system. Seeds may 

remain viable in the soil for 2-15 years.

 

Crown vetch: a) plant (Jan Samanek, State Phytosanitary Administration), b) infestation (James H. 

Miller, USDA Forest Service) (a,b www.bugwood.org)

a b
Family Fabaceae

New Invaders of the Northwest 57

HABITAT: Most often found in open meadows, 

grasslands, savannas, and forest edges. Capitalizes 

on disturbance so can be found along roadsides, 

in abandoned fields, and disturbed forests under 

conditions varying from dry and sunny to moist 

and semi-shaded.

LOOK-ALIKES: The pea-like flowers and the 

compound leaves help differentiate this species from 

other plants outside of the Fabaceae family. Within 

the family, a number of milkvetch (Astragalus) 

and vetch (Vicia) species resemble crown vetch. 

Milkvetch leaves also have a terminal leaflet, but 

they 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: Not listed as 

noxious in any western state or province.

NOTES: Though not listed as noxious anywhere, 

its ecological impact ranking and potential for 

distribution are both high. The plant is toxic to 

horses; if consumed in large amounts, it can cause slow 

growth, paralysis, or even death.

Crown vetch: c) leaves, d) flowers (c,d both Dan Tenaglia, Missouriplants.com, www.bugwood.org), 

e) fruits (Matt Lavin, Bozeman, Montana, USA)

Look-alike: vetch (Richard Old, 

www.xidservices.com, www.

bugwood.org)

c d e
Kudzu

Pueraria montana var. lobata (Willd.) Maesen & S. M. Almeida ex Sanjappa & Predeep

58 New Invaders of the Northwest PINKISH PURPLE FLOWERS SYNONYMS: Japanese arrowroot, Pueraria montana (Lour.) Merr., P. lobata 

(Willd.) Ohwi

ORIGIN: Asia

GROWTH TRAITS: Semi-woody, perennial vine growing from woody, tuberous 

roots. Roots can be >6’ long (1.8 m) and weigh up to 300 pounds. A single root 

can produce up to 30 vines, each growing up to 100’ long (30 m) in total and up 

to 1’ (30 cm) per day. Vines smother trees, shrubs, utility poles, etc., and form 

extensive mats on open ground. Young vines are green while older vines have 

brownish bark and are up to 4” (10 cm) in diameter. Stems (vines) regularly root 

from any node touching the ground. Leaves are alternate and compound. Each 

leaflet is 3-4” long (71⁄2-10 cm), dark green with lighter veins, and can be oval 

or goosefoot-shaped. Leaves and stems are hairy. Flowers appear in long clusters 

in late summer. Each flower is pea-like (having a banner, wing and keel, typical 

of the pea family), 1⁄2-3⁄4” (11⁄2-2 cm), and can be pink, purple, or red. Fruits are 

Kudzu: a) plant (Miya), b) large infestation in foreground and smothering other species in 

background (Galen Parks Smith)

a b
Family Fabaceae

New Invaders of the Northwest 59

flattened, hairy seed pods up to 2” long (5 cm) that 

turn dark brown at maturity.

REPRODUCTION: By seed (minimal) and 

vegetatively through rooting nodes (primary 

means). 

 

HABITAT: Found in open, disturbed areas such as 

abandoned fields, roadsides, and forest edges. It is 

most prolific in full sun, in deep, well-drained soils, 

and where winters are mild and annual rainfall high. 

LOOK-ALIKES: In the Northwest, the majority 

of climbing vines have very different flowers and 

a different number of leaflets. English ivy (Hedera helix) is sometimes mistaken 

for Kudzu, but has undivided and much smaller leaves. Western poison ivy 

(Toxicodendron rydbergii) has 3 leaflets with 

strong venation, but this species grows as a 

short shrub and has drooping white flower 

clusters and berry fruits. 

NOXIOUS WEED LISTINGS: OR (A), WA (A, 

Prohibited)

NOTES: Several species and varieties of kudzu are 

known, all with only subtle morphological differences. 

The majority of sources refer to the form invasive in 

North America as Pueraria montana var. lobata.

Kudzu: c) leaf (Rebekah D. Wallace, University of Georgia), d) flowers, e) fruits (d,e Leslie J. 

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

Look-alike: western poison ivy 

(Dave Powell, USDA Forest 

Service, www.bugwood.org)

c d e
Camelthorn

Alhagi maurorum Medik.

60 New Invaders of the Northwest PINKISH PURPLE FLOWERS SYNONYMS: Caspian manna, Persian manna, Alhagi camelorum Fisch., Alhagi 

pseudalhagi (M. Bieb.) Desv. ex B. Keller & Shap.

ORIGIN: Mediterranean, Eurasia

GROWTH TRAITS: Perennial shrub growing 2-3’ tall (0.6 to 0.9 m) from a 

deep and extensive rhizomatous root system. Stems and leaves are gray-green. 

Leaves are small, elliptic with smooth margins, and occur alternately up the 

stem. Sharp, yellow-tipped spines 1-2” long (21⁄2-5 cm) are produced in leaf axils. 

Small, pea-like flowers (having a banner, wing and keel, typical of the pea family) 

are produced from June to August. Flowers range from pink to maroon and are 

borne on short, spine-tipped branches. Reddish-brown seed pods are constricted 

between the individual seeds and are tipped with a small beak. Seeds are dark 

brown and kidney-shaped. Plant growth varies with environmental conditions; 

thorns are smaller and fewer and leaves are larger and more numerous in moister 

climates.

Camelthorn: a) plant section (John M. Randall, The Nature Conservancy, www.bugwood.org), 

b) large plant, from above (Eitan f)

a b
Family Fabaceae

New Invaders of the Northwest 61

REPRODUCTION: By seed and the rhizomatous 

root system. Seeds may remain viable in the soil for 

many years.

 

HABITAT: Found in moist to dry areas in disturbed 

soil.

LOOK-ALIKES: Though individual characteristics 

of camelthorn may resemble other plants, 

the combination of small, pink, and pea-like 

flowers, long spines, short height, and undivided, 

smooth-margined leaves help differentiate this 

species. Russian thistle (Salsola tragus) resembles 

camelthorn with its shrubby form and green, spiny 

stems. However, the exotic Russian thistle does not 

have showy pink flowers or elliptic leaves. 

NOXIOUS WEED LISTINGS: CA, CO NV 

& OR (A), WA (B)

NOTES: Seeds require scarification and do not 

germinate while exposed to light. Germination 

is highest following flash floods or after seeds pass 

through the digestive system of animals.

Camelthorn: c) leaves and thorns (Steve Dewey, Utah State University), d) flowers (Eitan f), e) seed 

pods from spine (John M. Randall, The Nature Conservancy) (c,e www.bugwood.org)

Look-alike: Russian thistle (Eric 

Coombs, Oregon Department of 

Agriculture, www.bugwood.org)

c d e
Bur & Wild chervil

Anthriscus caucalis M. Bieb. & A. sylvestris (L.) Hoffm.

62 New Invaders of the Northwest WHITE FLOWERS

Bur chervil: a) plant with flowers (Olivier Pichard), b) foliage (Joseph DiTomaso, University of 

California - Davis), c) fruits (D. Walters and C. Southwick, USDA) (b,c www.bugwood.org)

Wild chervil: d) plant with flowers, e) foliage, f) fruits - still attached (d-f Leslie J. Mehrhoff, 

University of Connecticut, www.bugwood.org) 

f

e

d

c

b

a
Family Apiaceae

New Invaders of the Northwest 63

SYNONYMS: Bur chervil (BC): Anthriscus scandicinus Mansf.; Wild chervil 

(WC): cow parsley, raven’s wing

ORIGIN: Eurasia (both species)

GROWTH TRAITS: Both species are herbaceous, taprooted, and generally less 

than 3’ tall (0.9 m) but may reach 6’ (1.8 m) on occasion. Stems are hollow 

and branching with alternate leaves that are 2-3 times divided, appearing fernlike. Leaves are larger at the plant base, have short, stiff hairs, and are gradually 

reduced in size upwards on the plant stem. Flowers are white and have 5 petals.

BC: Annual species that typically germinates in fall. Flowers are arranged in 

compound umbels at leaf axils and bloom in spring. Fruits are <1⁄4” long (6 mm), 

beaked, and covered with hooked hairs. WC: Annual, biennial, or short-lived 

perennial. Flowers are arranged in compound umbels at stem tips and bloom 

from spring through summer. Fruits are <1⁄4” long (6 mm), beaked, and smooth. 

REPRODUCTION: Both species spread only by seed. Seed viability is unknown. 

HABITAT: Both species frequent moist and disturbed areas along ditchbanks 

and in meadows, open forests, and irrigated pastures. BC can withstand drier 

conditions than WC.

LOOK-ALIKES:The combination of hollow stems, fern-like leaves, and 5-petaled 

white flowers arising from umbels help differentiate these species from many 

non-Apiaceae look-alikes. Examining the fruits can help differentiate species in 

the Apiaceae family. Both species resemble the related poison hemlock (Conium 

maculatum), a deadly species invasive in North America. Poison hemlock can 

grow much taller (10’ or 3 m) and has larger stems overall covered in small, 

purple spots. The umbel location (leaf axils rather than stem tips) and hair 

on fruits help differentiate bur 

chervil from wild chervil. 

NOXIOUS WEED LISTINGS:

BC: BC (Provincial); WC: BC 

(Regional), WA (B, Prohibited)

NOTES: The hooked hairs on bur chervil 

seeds readily adhere to fur, clothing, 

and objects.

Bur chervil Wild chervil
Giant hogweed

Heracleum mantegazzianum Sommier & Levier

64 New Invaders of the Northwest WHITE FLOWERS SYNONYMS: cartwheel flower

ORIGIN: Eurasia

GROWTH TRAITS: Herbaceous, short-lived perennial growing from a taproot 

and reaching 10-15’ tall (3-41⁄2 m) during flowering. The large stems are hollow 

and usually marked with purple, bumpy blotches. Leaves are deeply lobed, 

sharply pointed, and up to 3’ wide (0.9 m). The white flowers are on a large 

compound umbel (all flower stalks arising from the same point) that can be 

21⁄2’ (0.8 m) in diameter. Flowering occurs from late spring to early summer. 

Fruits are elliptic and when dry are marked with brown, swollen resin canals less 

than 1/16” (1 mm) in diameter. The plant typically grows several years before 

flowering, and then dies following flowering.

REPRODUCTION: By seed. Seeds are dormant the first year but can remain 

viable in the soil for many years.

 

Giant hogweed: a) plant (Fritz Geller-Grim), b) infestation (Jan Samanek, State Phytosanitary 

Administration, www.bugwood.org) 

a b
Family Apiaceae

New Invaders of the Northwest 65

HABITAT: Found in moist, disturbed soils such as 

riverbanks, ditches and railroad rights-of-way.

LOOK-ALIKES: Numerous species in the 

Apiaceae family are present in North America and 

resemble giant hogweed with their white umbel 

inflorescences and hollow stems. Only one species 

(common cowparsnip, Heracleum maximum) is 

large like giant hogweed and has massive lobed 

leaves. Common cowparsnip differs in that even at 

its maximum size, it can only reach heights of 10’ (3 

m) and has smaller leaves up to 18” (45 cm) wide. 

The native sweet coltsfoot (Petasites frigidus) can 

have very similar leaves to giant hogweed, however 

while giant hogweed grows as a rosette of leaves, 

coltsfoot leaves emerge from the soil on single 

stems. Also, sweet coltsfoot only grows up to 2’ 

tall (60 cm), and its inflorescences are clusters of 

flower heads with multiple white to pink florets. 

NOXIOUS WEED LISTINGS: AB (Prohibited), 

ID (EDRR), OR (A), WA (A, Prohibited)

NOTES: The plant produces sap that causes skin 

sensitivity to UV radiation and leads to blistering and 

severe burns. Consequently, great care should be taken 

when handling.

Giant hogweed: c) leaf (Sasha Shaw, King County NWCB), d) leaf attachment on stem (Richard 

Old, www.xidservices.com), e) flowers ( Frank Schwichtenberg), f) seed (USDA APHIS PPQ) 

(d,f www.bugwood.org)

Look alike: common cowparsnip 

(Richard Old, www.xidservices. 

com, www.bugwood.org)

c d e f
Cutleaf teasel

Dipsacus laciniatus L.

66 New Invaders of the Northwest WHITE FLOWERS SYNONYMS: cut-leaved teasel

ORIGIN: Eurasia

GROWTH TRAITS: Herbaceous perennial that grows from a taproot. The plant 

remains as a basal rosette for 1-3 years, after which it sends up flowering stalks 

that can reach 6-7’ (2 m) in height. Opposite leaves are fused at the base and 

form cups that surround the prickly stem. Leaves are deeply lobed, appearing 

fringed. Large, oval flower heads are covered in tiny white flowers, with each 

flower having a stiff, spiny bract. Even larger spiny bracts subtend the flower 

heads. Flowers bloom from June to September. The middle of the head blooms 

first, followed by the upper and lower parts.

REPRODUCTION: By seed. Seeds can be viable in the soil for more than three 

years, though the majority germinate within one.

 

Cutleaf teasel: a) plants, b) leaves (a,b Chris Evans, River to River CWMA, www.bugwood.org) 

a b
Family Dipsacaceae

New Invaders of the Northwest 67

HABITAT: Found in open, sunny habitats preferring 

roadsides and other disturbed waste areas, although 

it can sometimes be found in high quality habitats 

such as prairies, seeps, and meadows.

LOOK-ALIKES: The opposite and jagged leaves, 

prickly stems, and stiff flower heads subtended 

by long bracts help differentiate this species from 

unrelated look-alikes. Another species of invasive 

teasel, common teasel (Dipsacus fullonum), is very 

similar to cutleaf teasel, but has purple-colored 

flowers and leaves without deep teeth or lobes.

NOXIOUS WEED LISTINGS: CO & OR (B)

NOTES: Flower heads of many teasel species 

were once used to card wool.

Cutleaf teasel: c) infestation, d) prickly stem (Todd Pfeiffer, Klamath Country Weed Control), 

e) flower heads (c,e Chris Evans, River to River CWMA) (c-e www.bugwood.org)

Look-alike: common teasel 

(Ohio State Weed Lab Archive, 

Ohio State University, www.

bugwood.org)

c d e
Garlic mustard

Alliaria petiolata (M. Bieb.) Cavara & Grande

68 New Invaders of the Northwest WHITE FLOWERS SYNONYMS: hedge garlic, Alliaria officinalis Andrz. ex M. Bieb.

ORIGIN: Europe

GROWTH TRAITS: Herbaceous biennial that forms a rosette the first year and 

a 1-4’ tall (0.3-1.2 m) flowering stalk the second year. The root is a slender, white 

taproot, typically having a distinctive “s” curve at the top, just below the root 

crown. Basal leaves are rounded to kidney-shaped, and stems leaves are alternate 

and triangular. Both leaf types have coarse, wavy-toothed margins and are 1-6” 

long (21⁄2-15 cm). Small white flowers have 4 petals and 6 stamens and bloom in 

early spring. Seeds are produced in erect, slender pods that become brown when 

mature. By late summer plants can only be distinguished by the erect, leafless 

stalks with dry, brown seed pods. 

REPRODUCTION: By seed. Most seeds germinate once dormancy is broken; a 

small percentage remains viable in the soil for four or more years.

 

Garlic mustard: a) plant (Robert Vidéki, Doronicum Kft.), b) infestation (Steven Katovich, USDA 

Forest Service) (a,b www.bugwood.org)

a b
Family Brassicaceae

New Invaders of the Northwest 69

HABITAT: Found in moist, shaded soil of 

floodplains, forests, riverbanks, roadsides, and 

trailsides, capitalizing on disturbance.

LOOK-ALIKES: The four petals in combination 

with six stamens help differentiate this species from 

those outside the Brassicaceae. Within the family, 

most species in the Northwest have different colored 

flowers. Other invasive white-flowered mustards 

such as whitetop and perennial pepperweed can 

be distinguished by their leaves, which are not 

heart-shaped or deeply toothed. When growing as 

a rosette, garlic mustard resembles rosettes of the 

native piggy-back plant (Tolmiea menziesii) and fringecup (Tellima grandiflora). 

Piggy-back plant and fringecup are covered in long hairs while garlic mustard 

has few, short hairs. The exotic and weedy 

nipplewort (Lapsana communis) looks similar 

when young, but it is covered in whitish hairs, 

has white sap, and its leaves have a few smaller 

lobes below a larger terminal leaflet. 

NOXIOUS WEED LISTINGS: AB (Prohibited), 

BC (Provincial), OR (B), WA (A, Prohibited)

NOTES: Plant parts (especially when young) can give off 

a garlic odor when crushed.

Garlic mustard: c) s-shaped curve at top of root, d) leaf (Rob Routledge, Sault College), e) flowers (Leslie 

J. Mehrhoff, University of Connecticut), f) fruits (c,f Wendy DesCamp, Washington State Noxious 

Weed Control Board) (d,e www.bugwood.org)

Look-alike: piggyback plant 

(Edgeplot)

c d e f
Italian arum

Arum italicum Mill.

70 New Invaders of the Northwest WHITE FLOWERS SYNONYMS: Italian lords-and-ladies, orange candleflower, cuckoo’s pint

ORIGIN: Eurasia, Mediterranean

GROWTH TRAITS: Herbaceous, stemless perennial growing 1-11⁄2’ tall (30-45 

cm) 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 31⁄2-8” long (9-20 cm) 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 have veins colored silver-gray to yellow-green. Tiny white 

flowers are produced in spring on a long, narrow spadix surrounded by a large 

green spathe. The leaves and spathe die back after flowering, leaving only the 

spadix, which produces tight clusters of orange-red berries.

Italian arum: a) plant, b) infestation (Wendy DesCamp, Washington State Noxious Weed Control 

Board)

a b
Family Araceae

New Invaders of the Northwest 71

REPRODUCTION: By seed and vegetatively by 

daughter tubers. Seeds are reportedly only viable 

for a short time.

 

HABITAT: Found in open woodlands, forest edges 

and understories, open scrub, 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 and arrow-head leaves largely help distinguish 

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

arum (Calla palustris) occur in bogs and marshes.

NOXIOUS WEED LISTINGS: Not listed 

as noxious in any western state or province; 

proposed for listing in WA in 2015.

NOTES: Though not listed as noxious anywhere, 

its ecological impact ranking and potential for 

distribution are both high. In Washington, the plant 

appears to be leaving the lag phase and becoming more 

common. All parts of the plant are poisonous.

Italian arum: c) leaf (Hectonichus), d) spadix and portions of the spathe (Meneerke Bloem), 

e) berries (Wendy DesCamp, Washington State Noxious Weed Control Board)

Look-alike: water arum (Anneli 

Salo)

c d e
Mediterranean sage

Salvia aethiopis L.

72 New Invaders of the Northwest WHITE FLOWERS SYNONYMS: African sage

ORIGIN: Eurasia

GROWTH TRAITS: Herbaceous biennial growing 2-3’ tall (0.6-0.9 m) from 

a stout taproot. Rosette leaves are grayish-green, triangular with jagged teeth, 

and 4-12” long (10-30 cm). Stem leaves are opposite, smaller, and aromatic 

when crushed. Branching stems are square in cross-section. Stems, new leaves, 

and mature leaf undersides are all covered in fine, woolly hairs. Mature plants 

become less hairy and develop prominent venation on the leaves. Whitish flowers 

are bilabiate (2-lipped), clustered at stem tips, and bloom from June through 

August. Flowers form four 1-seeded nutlets that are oval-shaped, smooth, 

and brown. The leaf arrangement and the shape of the stems and flowers are 

characteristic of the Lamiaceae family.

Mediterranean sage: a) plant, b) infestation (a,b Eric Coombs, Oregon Department of Agriculture, 

www.bugwood.org) 

a b
Family Lamiaceae

New Invaders of the Northwest 73

REPRODUCTION: By seed. Seeds can be viable 

in the soil for up to 10 years.

 

HABITAT: Found in dry soils and disturbed habitats 

such as roadsides, pastures, and abandoned fields.

LOOK-ALIKES: The opposite leaves and square 

stems differentiate this plant from non-Lamiaceae 

look-alikes. Within the family, there are many 

native and exotic species of Salvia that resemble 

Mediterranean sage. Most look-alikes do not have 

white flowers; those which do (such as lyreleaf 

sage, Salvia lyrata) are not strongly 2-lipped. In 

addition, most Salvia look-alikes also have very 

different leaves and their inflorescences are not as 

large and branched as Mediterranean sage. 

NOXIOUS WEED LISTINGS: CO & NV 

(A), ID (Control), OR (B), WA (A, Prohibited)

NOTES: Stems bases break in autumn and spread 

seeds by tumbling with the wind.

Mediterranean sage: c) rosette leaves, d) flowers (c,d Pipi69e), e) seeds (Steve Hurst, USDA NRCS 

PLANTS Database, www.bugwood.org)

Look-alike: lyreleaf sage (David 

Stephens, www.bugwood.org)

c d e
Goatsrue

Galega officinalis L.

74 New Invaders of the Northwest WHITE FLOWERS SYNONYMS: professor weed

ORIGIN: Middle East

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

a deep taproot. Plants are shrubby 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 are white to light purple, 

pea-like (having a banner, wing and keel, typical of the pea family), and are 

arranged in clusters at stem tips or leaf axils. Flowering is from June to July. 

Fruits are narrow pods just over 1” long (3 cm). 

REPRODUCTION: By seed. Seeds can be viable in the soil for up to 10 years.

 

HABITAT: Found in or along cropland, ditchbanks, irrigation waterways, uncut 

pastures, fence lines, roadways and wet, marshy areas.

Goatsrue: a) plant (Sasha Shaw, King County NCWB), b) close-up of scattered infestation (Carl 

Bullock) 

a b
Family Fabaceae

New Invaders of the Northwest 75

LOOK-ALIKES: The unique, pea-like flowers as 

well as 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: NV & OR (A), 

WA (A, Prohibited)

NOTES: 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 toxic in 

large quantities.

Goatsrue: c) leaves with leaflets, d) flowers (H. Zell), e) seed pods (c,e Sasha Shaw, King County 

NWCB) 

Look-alike: vetch (Richard Old, 

www.xidservices.com, www.

bugwood.org)

c d e
Bridal veil broom

Retama monosperma (L.) Boiss.

76 New Invaders of the Northwest WHITE FLOWERS SYNONYMS: Genista monosperma (L.) Lam., Spartium monospermum L., Lygos

monosperma (L.) Heywood

ORIGIN: Mediterranean

GROWTH TRAITS: Upright, perennial shrub growing up to 10’ tall (3 m) and 

20’ across (6 m) from a deep taproot. Young plants are dominated by a leading 

stem; plants become more branched and broaden with age. Stems are slender, 

green, and drooping. Leaves are small, linear, and usually simple (not divided 

into leaflets). Leaves are quickly deciduous so stems are leafless much of the year. 

Flowers are small, have purple sepals, and have petals that are white and pea-like 

(having a banner, wing and keel, typical of the pea family). Flowers appear in 

short clusters of 2-20 from the stems in early spring, though some plants have 

been observed flowering year-round in warm climates. The fruits are pods that 

are nearly circular, typically 0.4” long (1 cm), and contain 1-2 seeds each. 

Bridal veil broom: a) plant (Javier Martin), b) infestation prior to blooming (Jean-Paul Peltier) 

a b
Family Fabaceae

New Invaders of the Northwest 77

REPRODUCTION: By seed. Seeds may remain 

viable in the soil for several years.

 

HABITAT: Does well in dry, rocky, infertile soils 

such as sage scrub, chaparral, and grasslands.

LOOK-ALIKES: Multiple exotic broom species are 

established in similar habitats in North America, 

such as Scotch broom (Cytisus scoparius) and 

Spanish broom (Spartium junceum). These other 

brooms resemble bridal veil broom when not in 

bloom or not fruiting. Their larger yellow flowers 

and long seed pods containing more seeds help 

differentiate them from bridal veil broom which 

has small white flowers, nearly circular pods, and 

typically only one seed per pod.

NOXIOUS WEED LISTINGS: CA

NOTES: Likely an escaped ornamental. In southern 

California, an infestation grew from 10 acres (4 ha) 

to over 2,000 acres (809 ha) in 6 years. It was recently 

reported from the Columbia River Gorge (Hood River 

County, Oregon).

Bridal veil broom: c) stems and leaves (James Gaither), d) flowers (Javier Martin), e) fruits (Fouad 

Msanda)

Look-alike: Scotch broom 

(Steve Dewey, Utah State 

University, www.bugwood.org)

c d e
Common privet

Ligustrum vulgare L.

78 New Invaders of the Northwest WHITE FLOWERS SYNONYMS: European privet, wild privet

ORIGIN: Europe, Mediterranean

GROWTH TRAITS: Perennial shrub that grows 10-15’ tall (3-4.8 m) from a 

shallow root system. Plants are typically deciduous but may be evergreen in mild 

climates. Multiple stems have smooth, gray-brown bark and produce several 

long, leafy branches. Stems can root when they touch the ground, leading to 

a sprawling growth form. Leaves are opposite, elliptic, narrow, and grow up 

to 21⁄2” long (6 cm). Leaves have smooth margins and a deep midvein. Flowers 

appear in spring to early summer in clusters at the ends of branches. Each small 

flower has 4 white petals that are free at their tips but fused at their bases, giving 

them a tubular appearance. Fruits are berries that turn from green to shiny black 

with maturity. Each berry has up to 4 seeds.

REPRODUCTION: By seed and by producing roots when stems touch the 

ground. Seeds remain viable for only one year.

 

Common privet: a) plant, b) infestation (a,b Robert Vidéki, Doronicum Kft., www.bugwood.org) 

a b
Family Oleaceae

New Invaders of the Northwest 79

HABITAT: Frequently occurs in edge habitats such 

as roadsides, fence rows, and bottom-land forests, 

before expanding into woods and abandoned fields.

LOOK-ALIKES: Numerous shrub species 

superficially resemble common privet. The 

combination of opposite leaves, 4-petal white 

flowers, brown stems, and a single leaf midvein all 

help differentiate common privet from potential 

look-alikes. Several other privet species occur in 

North America, such as Chinese privet (Ligustrum 

sinensis); all are exotic and many are highly invasive. 

The color of fruits and leaves, shape of leaves and 

flowers, and presence of hair on stems and flowers 

help differentiate privet species from each other. 

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any western state or province.

NOTES: Though not listed as noxious anywhere, 

its ecological impact ranking and potential for 

distribution are both high. Berries are poisonous 

to humans but readily eaten by birds.

Common privet: c) leaves, d) flowers, e) fruits (a-c Robert Vidéki, Doronicum Kft., www.bugwood.org)

Look-alike: Chinese privet 

(Karan A. Rawlins, University 

of Georgia, www.bugwood.org)

c d e
Syrian beancaper

Zygophyllum fabago L.

80 New Invaders of the Northwest WHITE FLOWERS SYNONYMS: Syrian bean-caper

ORIGIN: Eurasia

GROWTH TRAITS: Typically a shrubby perennial growing up to 3’ tall (0.9 

m) from a deep, woody taproot with creeping rhizomes. In cold climates, the 

plant may behave as an annual. Stems are multi-branched and hairless. Leaves 

are opposite and each composed of 2 leathery, oval-shaped leaflets. Leaflets have 

smooth margins and are up to 1” long (21⁄2 cm). Flowers appear on stalks at leaf 

axils from spring through early summer. Flowers have 5 green sepals and 5 white 

or cream petals with salmon-colored markings. The 10 stamens are orangish and 

extend beyond the petals. Fruits are 5-celled, drooping capsules up to 11⁄2” long 

(4 cm) that open at maturity to release the small, dark seeds.

REPRODUCTION: By seed, rhizomes, and root fragments. It is unknown how 

long seeds may remain viable in the soil.

 

Syrian beancaper: a) plant (Philmarin), b) infestation (Javier Martin) 

a b
Family Zygophyllaceae

New Invaders of the Northwest 81

HABITAT: Found in dry, open habitats with welldrained soil including rangeland, roadsides, and 

desert areas.

LOOK-ALIKES: The opposite compound leaves, 

white flowers with exerted orange stamens, hanging 

capsule fruit, and shrubby growth form are not 

found in combination on any possible look-alike. 

Most species resembling Syrian beancaper have 

two or less of those traits. Various species in the 

Fabaceae may resemble young and small Syrian 

beancaper, including alfalfa, sweetclover, and 

medick. These can be distinguished by having 3 

leaflets on alternate leaves and pea-like flowers. 

Common snowberry (Symphoricarpos albus) is a shrub with opposite leaves and 

whitish flowers; however its leaves are not compound or leathery, its flowers 

occur in small drooping pairs, its fruits are 

white berries, and it typically grows in more 

moist habitats than Syrian beancaper. 

NOXIOUS WEED LISTINGS: CA, CO 

(Watch List), ID (EDRR), NV & OR (A), WA 

(A, Prohibited)

NOTES: The flowers have a taste and scent similar to 

caper.

Syrian beancaper: c) leaflets, flower, and immature fruit (Dell O. Clark, California Department of 

Food and Agriculture, www.bugwood.org), d) flower, e) split fruits and seeds (d,e Philmarin)

Look-alike: common snowberry 

(Frank Vincentz)

c d e
English holly

Ilex aquifolium L.

82 New Invaders of the Northwest WHITE FLOWERS SYNONYMS: holly, European holly

ORIGIN: Europe, Mediterranean

GROWTH TRAITS: Upright, perennial shrub or tree growing 15-50’ tall (41⁄2-

15 m) and up to 15’ wide from a fleshy, deep, and extensive root system. Plants 

may have a single trunk or form a multi-branched thicket. Stems touching the 

ground readily root, leading to plant spread. Stem bark is gray and smooth or 

nearly smooth. Leaves are alternate, 2-4” long (5–10 cm), dark and evergreen, 

thick, wavy, and glossy. Leaves on young and lower branches have sharp, spinetipped margins; leaves on upper branches of older trees have smooth margins. 

Flowering occurs from spring to early summer. Plants have either male or female 

flowers; both have 4 dull-white petals. Male flowers have 4 stamens, while 

female flowers have an obvious green ovary. Female flowers produce red, yellow, 

or orange berry-like fruits.

REPRODUCTION: By seed and vegetatively via suckering or when stems root 

after touching the ground. Seeds typically remain viable for at least three years.

 

English holly: a) plant (H. Zell), b) new and spreading infestation (Forest & Kim Starr)

a b
Family Aquifoliaceae

New Invaders of the Northwest 83

HABITAT: Prefers moist, cool, forested conditions 

and undisturbed, well-drained soil. Can tolerate 

full sun.

LOOK-ALIKES: The thick, glossy, wavy, and 

sharply spiny leaves differentiate English holly 

from most potential look-alikes. The native tall 

Oregon grape (Berberis aquifolium) grows in 

similar habitats and has leaflets which resemble the 

leaves of English holly. However, tall Oregon grape 

grows as a much smaller shrub (up to 8’ or 2.4 m 

tall) and has leaves divided into pairs of opposite 

leaflets, dark blue berries, and flowers with 6 bright 

yellow sepals and 6 bright yellow petals.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any western state or province.

NOTES: Though not listed as noxious anywhere, 

its ecological impact ranking and potential 

for distribution are both high. In Washington, 

the plant appears to be leaving the lag phase and 

becoming more common. Berries are poisonous to 

humans, but are readily consumed by birds.

English holly: c) leaves (Luis Miguel Bugallo Sánchez), d) female flowers (Meneerke Bloem), 

e) fruits (Jürgen Howaldt)

Look-alike: tall Oregon grape 

(Meggar)

c d e
Austrian & Creeping yellow cress

Rorippa austriaca (Crantz) Besser & R. sylvestris (L.) Besser

84 New Invaders of the Northwest YELLOW FLOWERS

Austrian yellow cress: a) basal leaves, b) flowers, c) fruits (a-c Elizabeth Bella, USDA, bugwood.org)

Creeping yellow cress: d) plant (Joseph DiTomaso, University of California - Davis, www.bugwood.

org), e) flowers and leaves (SB Johnny), f) fruits (Robert Mohlenbrock, USDA SCS, USDA 

PLANTS Database) 

f

e

d

c

b

a
Family Brassicaceae

New Invaders of the Northwest 85

SYNONYMS: Austrian yellow cress (AYC): Austrian fieldcress, Nasturtium 

austriacum Crantz; Creeping yellow cress (CYC): creeping fieldcress

ORIGIN: Eurasia (both species)

GROWTH TRAITS: Both species are herbaceous perennials that have taproots 

and develop rhizomes. Stems are 1-3’ tall (0.3-0.9 m). Flowers have 4 petals and 

6 stamens, are arranged alternately on short stalks along stem tips, and appear 

from late spring through summer. AYC: Stem leaves are alternate, 1-2” long 

(21⁄2-5 cm), oblong, hairless, and can have slightly or very toothed margins. 

Basal leaves are twice as long (up to 4” or 10 cm) and deeply lobed, sometimes 

appearing dissected. Stems are slightly hairy, and upper leaves clasp the stem. 

Flowers are yellow and 1⁄4” (1⁄3 cm) in diameter. Fruits are small and spherical 

but are rarely produced. CYC: Plants often form a dense, creeping mat. Leaves 

are more finely divided than AYC, growing up to 8” long (20 cm). Flowers are 

yellow and less than 1⁄8” (0.6 cm) in diameter. Fruits are long (0.4” or 1 cm), very 

thin, and somewhat constricted. 

REPRODUCTION: Both species spread primarily by rhizomes.

 

HABITAT: Both species frequent moist and disturbed areas along roadsides, 

fields, and pastures. CYC almost always occurs near water.

LOOK-ALIKES: Many Brassicaceae in the Northwest have similar flowers and 

leaves. The exact combination of leaf shape, short stature, moist habitat, and 

small flower size differentiate these species from others. The rounded fruit of 

AYC differentiates it from the long, slender-fruited CYC. 

NOXIOUS WEED LISTINGS: AYC: AK (Prohibited), CA, NV (A), WA (C); 

CYC: CA, OR (B)

NOTES: Both species are 

considered weedy in portions 

of Europe; their hybrid is more 

invasive there than either species 

alone.

Austrian yellow cress Creeping yellow cress
Yellowtuft

Alyssum corsicum Duby & A. murale Waldst. & Kit.

86 New Invaders of the Northwest YELLOW FLOWERS

Alyssum corsicum: a) plant, b) leaves (Suzanne Vautier, Oregon Department of Agriculture, 

c) inflorescences (a,c Ken French, Oregon Department of Agriculture)

Alyssum murale: d) plant, e) leaves (Suzanne Vautier, Oregon Department of Agriculture), f) flowers 

(d,f © Kyle Strauss, The Nature Conservancy)

f

e

d

c

b

a
Family Brassicaceae

New Invaders of the Northwest 87

SYNONYMS: Not applicable to either species

ORIGIN: A. corsicum: Mediterranean; A. murale: Mediterranean, Eurasia

GROWTH TRAITS: Both species are herbaceous perennials growing up to 3.2’ 

tall (1 m) from a strong and fibrous root system. They produce hundreds of 

small, bright yellow flowers on branched umbels in early summer. Flowers have 

4 petals and 6 stamens. Most leaves (the distinctive feature) are shed prior to 

the initiation of flowering, making the two species look nearly identical. Fruits 

are round and small (less than 0.2” or 5 mm in diameter). They are flattened, 

papery, and each contains a single seed. Alyssum corsicum leaves are alternate 

and rounded but wider at the tips than the bases. They are densely covered in 

silver hairs, giving leaves a whitish-green appearance. Alyssum murale leaves are 

alternate, more linear, and up to 1.2” (3 cm) long. They are covered with tiny 

hairs that give the leaves a dusty appearance, not nearly as silvery as A. corsicum.

REPRODUCTION: Both species spread by seed and can re-sprout from root 

systems left intact in the soil. It is unknown how long seeds remain viable.

 

HABITAT: Both species are adapted to serpentine soils, as well as variable and 

harsh conditions. They can be found in pastures, fields, and waste areas in full 

sun to shaded understory.

LOOK-ALIKES: The symmetric flowers with four petals and six stamens help 

differentiate these species from non-Brassicaceae look-alikes. Several native and 

exotic Brassicaceae also have yellow flowers, however these two species can be 

differentiated by their combination of height (up to 1 m), umbel inflorescences, 

and deciduous leaves prior to flowering. Leaf shape and coloration help 

differentiate these species from each other.

NOXIOUS WEED LISTINGS:

Both species: OR (A)

NOTES: As hyperaccumulators, both 

species were intentionally introduced 

to Oregon to clean up contaminated 

mining sites, but escaped the project 

area and spread. 

Alyssum corsicum Alyssum murale
Garden loosestrife

Lysimachia vulgaris L.

88 New Invaders of the Northwest YELLOW FLOWERS SYNONYMS: yellow loosestrife

ORIGIN: Eurasia, northern Africa

GROWTH TRAITS: Upright, herbaceous perennial typically growing 3-6’ tall 

(1-1.9 m) from rhizomatous roots. Stems are hairy and may be branched near 

the top. Leaves are opposite or whorled in groups of 3 or 4. Leaves are lanceshaped, up to 5” long (121⁄2 cm), softly hairy, and dotted with black or orange 

glands. Flowers bloom throughout summer in long clusters at stem tips and in 

leaf axils. Each flower is 1⁄2” (11⁄4 cm) in diameter and has 5 yellow petals whose 

bases are fused and often have orange coloring. The 5 sepals are orange-tipped. 

Fruits are small, round capsules that split apart at maturity to spill seeds.

REPRODUCTION: By seed and rhizomes. Seeds are viable for up to 20 years.

 

Garden loosestrife: a) plant, b) infestation (a,b King County NWCB)

a b
Family Primulaceae

New Invaders of the Northwest 89

HABITAT: Found in moist areas, including wetlands, 

riparian corridors, and shores of lakes and ponds.

LOOK-ALIKES: From afar, several species resemble 

garden loosestrife, including several goldenrods 

(Solidago spp.). The opposite or whorled leaves 

and larger, separate flowers help differentiate 

garden loosestrife from potential look-alikes. A 

closely related ornamental species that is also called 

garden or yellow loosestrife (Lysimachia punctata) 

is very similar in appearance. Lysimachia punctata 

typically occurs in drier habitats, is unbranched, 

and its flowers are clustered in leaf axils rather than 

at stem tips.

NOXIOUS WEED LISTINGS: WA (B, 

Prohibited)

NOTES: Appears to outcompete the highly 

invasive (but unrelated) purple loosestrife 

(Lythrum salicaria).

Garden loosestrife: c) whorled leaves (Bff), d) flower (King County NWCB), e) fruits (Leslie J. 

Mehrhoff, University of Connecticut, www.bugwood.org)

Look-alike: yellow loosestrife 

(Wendy DesCamp, Washington 

State Noxious Weed Control 

Board)

c d e
Sicilian starthistle

Centaurea sulphurea Willd.

90 New Invaders of the Northwest YELLOW FLOWERS SYNONYMS: sulphur knapweed

ORIGIN: Mediterranean

GROWTH TRAITS: Upright, herbaceous winter annual typically growing 1-3’ 

tall (1⁄3-1 m) from a taproot. Large plants are branched; small plants have a single 

stem. Stems have wings ~1⁄4” wide (5-6 mm) at their largest. Leaves are alternate, 

may be lightly toothed or lobed, and become smaller up the plant. Leaves and 

wings are yellow-green and sparsely covered with stiff hairs. Flowering occurs 

from May to July when 1” (21⁄2 cm) flower heads develop singly at the ends of 

stems. Florets are yellow and numerous. Floral bracts are tipped with 3-5 pairs of 

small spines and a central main spine up to 1” long (21⁄2 cm). Spines are strawcolored at their tips and dark brown at their bases. Seeds are 1⁄4-1⁄3” long (5-8 

mm), glossy, brownish-tan, and with dark brown pappus as long as seeds.

Sicilian starthistle: a) plant with immature capitula, b) senescing infestation (a,b Joseph DiTomaso, 

University of California - Davis, www.bugwood.org)

a b
Family Asteraceae

New Invaders of the Northwest 91

REPRODUCTION: By seed. It is unknown how 

long seeds remain viable in the soil, but seeds of 

related species are viable for up to three years. 

 

HABITAT: Open, disturbed sites including 

grasslands, fields, pastures, roadsides, and waste 

places.

LOOK-ALIKES: The spiny capitula help 

differentiate this species from non-starthistle 

species in the Northwest. Yellow florets separate 

this species from purple-colored starthistles. Malta 

and yellow starthistle (Centaurea melitensis and 

C. solstitialis, both exotic) have yellow florets, but 

both have gray-green foliage due to numerous 

white cottony hairs. Flower heads of Sicilian 

starthistle are larger than Malta and yellow 

starthistle, and Sicilian starthistle seeds are twice 

as large and darker than seeds of the other two. 

NOXIOUS WEED LISTINGS: CA

NOTES: Where the species co-occur, Sicilian starthistle 

often out-competes yellow starthistle.

Sicilian starthistle: c) leaves and winged stem (Joseph DiTomaso, University of California - Davis, 

www.bugwood.org), d) flowering capitulum, e) senescing capitulum with seeds, from above 

(d,e Daniel Montesinos)

Look-alike: yellow starthistle 

(Jennifer Andreas, Washington 

State University Extension)

c d e
Smooth & Woolly distaff thistle

Carthamus creticus L. & C. lanatus L.

92 New Invaders of the Northwest YELLOW FLOWERS

Smooth distaff thistle: a) plants (©2001 CDFA), b) capitula, c) seeds (b,c Zoya Akulova)

Woolly distaff thistle: d) plant (Javier Martin), e) capitulum, f) seeds (e,f Philmarin) 

f

e

d

c

b

a
Family Asteraceae

New Invaders of the Northwest 93

SYNONYMS: Smooth distaff thistle (SDT): Carthamus baeticus (Boiss. & Reut.) 

Pérez Lara, C. lanatus L. ssp. baeticus (Boiss. & Reut.) Nyman, C. lanatus L. ssp. 

creticus (L.) Holmboe; Woolly distaff thistle (WDT): downy safflower, saffron 

thistle, C. lanatus L. ssp. lanatus

ORIGIN: SDT: Mediterranean, WDT: Mediterranean, Eurasia

GROWTH TRAITS: Both species are herbaceous winter annuals growing upright 

to 3.2’ tall (1 m) from slender, fibrous taproots. Stems are straw-colored. Stems 

and leaves are covered in tiny glandular hairs. Stem leaves are alternate, stiff, 

weakly clasp the stem, and often spread backwards. Leaves have lobes tipped with 

sharp spines. Basal leaves are larger than stem leaves and are typically absent at 

flowering. Flower heads appear solitary on stem tips in summer. Each capitulum 

has several rows of bracts and yellow florets. Outer bracts are stiff, leaf-like, and 

spread backward; inner bracts are smaller, spiny, and less lobed. Seeds are brown 

achenes. Outer seeds are rough and lack pappus; inner seeds are smoother with 

stiff, persistent pappus. SDT: Hairs on stems, leaves, and flower heads are only 

slightly woolly. Seed pappus is 0.3-0.4” long (8-10 mm). WDT: Hairs on stems, 

leaves, and flower heads are very woolly. Seed pappus is 0.4-0.5” long (10-13 mm). 

REPRODUCTION: Both species spread by seed only. Most seeds germinate 

within three years, though some may remain viable in the soil for eight.

 

HABITAT: Both species are found at disturbed, open sites including agricultural 

fields (especially grain), grasslands, and pastures.

LOOK-ALIKES: Their spiny nature differentiates these species from nonthistle look-alikes. Most other thistles do not have yellow florets or stiff, thick, 

backward-spreading leaves. Golden thistle (Scolymus hispanicus) is similar but 

has milky sap and winged stems. 

NOXIOUS WEED LISTINGS:

SDT: CA, OR (A); WDT: CA, 

CO (Watch List), OR (A)

NOTES: Both weeds are sometimes 

classified as subspecies of Carthamus 

lanatus. Their gene numbers differ, 

however, and the species do not 

hybridize. Smooth distaff thistle Woolly distaff thistle
Stinkwort

Dittrichia graveolens (L.) Greuter

94 New Invaders of the Northwest YELLOW FLOWERS SYNONYMS: stinkweed, camphor inula, cape khakiweed, Erigeron graveolens L.,

Inula graveolens (L.) Desf.

ORIGIN: Mediterranean

GROWTH TRAITS: Herbaceous annual typically growing 8-30” tall (20-75 

cm) from a taproot with extensive, smaller side roots. Stems are multi-branched. 

The entire plant is sticky to the touch, being covered in small, white, and slightly 

glandular hairs with a strong camphor-like odor. Stems and branches are covered 

in alternate, linear leaves 0.4-11⁄2” long (1-4 cm). Flower heads are produced in 

leaf axils and stem tips throughout fall. Each capitulum is 0.2-0.3” in diameter 

(5-7 mm). Outer florets are yellow and larger than inner florets which are yellow 

to red. Seeds are brown, oval achenes with a hairy pappus. 

REPRODUCTION: By seed. Seeds remain viable in the soil for up to three years.

 

Stinkwort: a) plant, b) infestation (a,b Javier Martin)

a b
Family Asteraceae

New Invaders of the Northwest 95

HABITAT: Primarily invades disturbed, open 

habitats, such as cultivated land, abandoned fields, 

overgrazed pastures, roadsides, and tidal margins.

LOOK-ALIKES: With its narrow leaves and bushy 

appearance, stinkwort resembles young Russian 

thistle (Salsola tragus) and kochia (Bassia scoparia), 

though its yellow flower heads and sticky, odorous 

foliage help differentiate it from these look-alikes. 

Many tarweeds (Centromadia, Hemizonia and 

Holocarpha spp.) are sticky, odorous, and have 

yellow flower heads. However, their foliage often 

appears more spiny than stinkwort, and their flower 

heads are typically larger. The native mountain 

tarweed (Madia glomerata) has small yellow flower heads, linear leaves, and is 

sticky and odorous. However, mountain tarweed grows much smaller and less 

branched, and its flower heads are typically 

clumped.

NOXIOUS WEED LISTINGS: Not listed as 

noxious in any western state or province.

NOTES: Though not listed as noxious anywhere, its 

ecological impact ranking and potential for distribution 

are both high. Touching the foliage can cause dermatitis, 

itchy skin, or blistering. When grazed, this plant can 

cause milk or meat to be tainted.

Stinkwort: c) leaf, bud, and stem (Javier Martin), d) flower head, e) mature achenes, still attached 

(d,e ©2014 Keir Morse)

Look-alike: mountain tarweed 

(Matt Lavin, Bozeman, MT, 

USA)

c d e
Spurge flax

Thymelaea passerina (L.) Coss. & Germ.

96 New Invaders of the Northwest YELLOW FLOWERS SYNONYMS: annual thymelaea, Stellera passerina L.

ORIGIN: Eurasia, northern Africa

GROWTH TRAITS: Herbaceous annual growing 21⁄2” to 2’ tall (6-60 cm) from 

a fibrous taproot. It may grow as a single stem, but more commonly the main 

stem splits into numerous branches in its upper reaches. Stems are slender and 

wiry. Leaves are alternate, leathery, and narrow with a tapered point. Leaves can 

be up to 1” long (21⁄2 cm) but gradually become smaller up the stem. Flowers 

occur in leaf axils in summer. Each flower is yellowish-green, tubular, and small 

(2-3 mm long). Flowers have 4 sepals, no petals, and 8 stamens that appear in 

two whorls of 4. Each flower is subtended by 2 small bracts arising from a tuft 

of tiny white hairs. Fruits enclose single seeds that are 2-3 mm long, teardropshaped, and brown to black.

Spurge flax: a) plant, b) multiple branches and stems (a,b Stefan Lefnaer)

a b
Family Thymelaeaceae

New Invaders of the Northwest 97

REPRODUCTION: By seed. It is unknown how 

long seeds remain viable in the soil.

 

HABITAT: Found in dry areas, including rangeland, 

pastures, abandoned fields, and roadsides.

LOOK-ALIKES: Several native and exotic species 

resemble spurge flax by having wiry stems, narrow 

leaves, and small flowers in leaf axils. Spurge flax 

can be differentiated by having 4 yellow-green 

sepals forming a tubular flower with 8 stamens. 

The look-alike Douglas’s knotweed (Polygonum 

douglasii) also has 8 stamens (though not in two 

whorls of 4). Douglas’s knotweed has star-shaped 

flowers with 5 whitish petals.

NOXIOUS WEED LISTINGS:

WA (A, Prohibited)

NOTES: Reportedly not palatable to livestock. The 

plant’s narrow growth form can make it difficult to 

distinguish from other vegetation. Seeds are frquently 

spread by ATVs.

Spurge flax: c) leaves, stem and bud (Stefan Lefnaer), d) flowers in leaf axils (John D. Draeger), 

e) seed (Robert J. Gibbons)

Look-alike: Douglas’s knotweed 

(Patrick J. Alexander, USDANRCS PLANTS Database)

c d e
Velvetleaf

Abutilon theophrasti Medik.

98 New Invaders of the Northwest YELLOW FLOWERS SYNONYMS: China jute

ORIGIN: Asia

GROWTH TRAITS: Upright, herbaceous annual typically growing 3-7’ tall (1-

2.1 m) from a taproot. Stems are very stout and stiff. Leaves are alternate, up 

to 8” long and wide (20 cm), and heart-shaped with slightly scalloped margins. 

Stems, branches, and both surfaces of leaves are covered in soft, short hairs 

that give the plant a velvety texture. Flowers occur singly in leaf axils from July 

through September. Flowers are up to 1” (2 1⁄2 cm) in diameter and have 5 

yellow petals and numerous stamens. Petals are narrower at their base. Fruits are 

round capsules 3⁄4” (2 cm) in diameter that consist of 12-15 clustered seed pods. 

Each seed pod has a beak curving backwards from the capsule. Capsules are dark 

brown at maturity. Seeds are small, brown, and kidney-shaped. 

REPRODUCTION: By seed. Seeds may remain viable for 20-50 years.

 

Velvetleaf: a) plant (Jan Samanek, State Phytosanitary Administration), b) infestation on a field edge 

(Phile Westra, Colorado State University) (a,b www.bugwood.org)

a b
Family Malvaceae

New Invaders of the Northwest 99

HABITAT: Found along roadsides, ditches/

riverbanks, hillsides, crop fields, and disturbed 

areas.

LOOK-ALIKES: Individual characteristics of 

velvetleaf may resemble other plants, but the 

combination of large heart-shaped leaves, an erect 

growth form, 5-petaled yellow flowers, and velvety 

texture help differentiate this species. Common 

sunflower (Helianthus annuus) grows in similar 

habitats and has large, alternate leaves and dark 

clustered fruits that can resemble those of velvetleaf 

following flowering. However, common sunflower 

has a distinctive inflorescence with multiple yellow 

and brown florets, and the plant is not velvety-soft.

NOXIOUS WEED LISTINGS:

BC (Provincial), CO (C), OR (B), WA (B, 

Prohibited)

NOTES: Introduced to North America as a potential 

fiber source, but escaped cultivation to become an 

invasive species of agricultural fields.

Velvetleaf: c) leaf (Jennifer Andreas, Washington State University Extension), d) flower and fruit 

(Joseph DiTomaso, University of California, Davis), e) seeds (c,e Bruce Ackley, The Ohio State 

University) (d-e www.bugwood.org)

Look-alike: common sunflower 

(Michael J. Plagens)

c d e
Yellow archangel

Lamiastrum galeobdolon (L.) Ehrend. & Polatschek

100 New Invaders of the Northwest YELLOW FLOWERS SYNONYMS: aluminum plant, golden dead-nettle, silverfrost, Lamium 

galeobdolon (L.) L., Galeopsis galeobdolon L.

ORIGIN: Eurasia

GROWTH TRAITS: Herbaceous, fast-growing perennial that can form a dense, 

trailing groundcover. Plants can grow upright to 2’ tall (60 cm) if growing over 

other plants. Roots are dense and fibrous; plants can also root from stem nodes. 

Stems are square in cross-section. Leaves are typically evergreen, opposite, 

variegated, oval-shaped, toothed, deeply veined, and hairy. In cold climates, 

leaves may develop purple coloring on both sides. Flowers bloom in early spring 

on upright stems and are bilabiate (2-lipped) with the upper lip hooded. Flowers 

are yellow, have orange to brown markings on the lower lip, and occur in whorls 

in leaf axils. Each flower produces four 1-seeded nutlets. The leaf arrangement 

and the shape of the stems and flowers are characteristic of the Lamiaceae family.

Yellow archangel: a) plant (Wouter Hagens), b) upright flowering infestation (Wendy DesCamp, 

Washington State Noxious Weed Control Board)

a b
Family Lamiaceae

New Invaders of the Northwest 101

REPRODUCTION: Primarily by sprouting/

rooting from stem nodes and stem fragments, but 

also by seed. Seed viability is unknown.

 

HABITAT: Found from full shade to full sun under 

moist to dry conditions. The plant is tolerant 

of frost, but is limited by dry, hot conditions. 

Frequent in forest understory, riparian areas, and 

moist hillsides.

LOOK-ALIKES: The opposite leaves and square 

stems differentiate this plant from non-Lamiaceae 

look-alikes. Within the family, the varietated leaves 

and yellow flowers help differentiate this species 

from look-alikes such as the exotic white deadnettle 

(Lamium album).

NOXIOUS WEED LISTINGS: OR & WA (B)

NOTES: This species is a popular ornamental 

groundcover and is used in decorative hanging 

baskets but frequently escapes cultivation.

Yellow archangel: c) leaves (Alison Halpern), d) leaves with purple winter coloring (Wendy 

DesCamp), e) flowers (Teun Spaans), f) fruits (Nisa Karimi, Wisconsin Department of Natural 

Resources, www.bugwood.org (c,d Washington State Noxious Weed Control Board)

Look-alike: white deadnettle 

(H. Zell)

c d e f
Oriental & Yellow clematis

Clematis orientalis L. & C. tangutica (Maxim.) Korsh.

102 New Invaders of the Northwest YELLOW FLOWERS

Oriental clematis: a) infestation (Wendy DesCamp, Washington State Noxious Weed Control 

Board), b) leaf, c) flower, d) mature fruit and vines (b-d Sue Bird, Yakima County NWCB)

Yellow clematis: d) plants (Steve Law, Henfield, England), e) flowers and leaves (Anneli Salo), 

f) mature fruit and leaf (Anneli Salo) 

f

e

d

c

b

a

c
Family Ranunculaceae

New Invaders of the Northwest 103

SYNONYMS: Oriental clematis (OC): Chinese clematis, Oriental virgin’s-bower, 

orange-peel clematis; Yellow clematis (YC): orange-peel clematis

ORIGIN: Eurasia (both species)

GROWTH TRAITS: Both species are perennial climbing vines (typical) or 

scrambling shrubs (atypical) growing from a fine, branched root system. Vines 

(stems) are pliable when young, becoming woody with age. Vines are typically 

≤13’ long (4 m). Vines smother trees, shrubs, walls, utility poles, etc. by climbing 

with tendril-like petioles. Leaves are compound, green, opposite, and deciduous. 

Each leaf has 5-7 lance-shaped and lobed leaflets. Both species have drooping 

flowers with 4 showy, yellow, petal-like sepals. Sepals may be tinged purplish. 

Flowering occurs in late summer. At maturity, the fruit consists of numerous 

small seeds, each with a long silky tail ~2” long (5 cm) that give the fruit a pompom appearance. OC: Vines growing up into trees can be up to 26’ long (8 m). 

Sepals are pale yellow, separate, and often recurved at maturity. Flowers occur 

singly or in small clusters in leaf axils, on flower stalks up to 4.3” long (11 cm). 

YC: Sepals are lemon yellow and bell-shaped at first but split and spread slightly 

at maturity. Flowers are typically solitary but sometimes occur in groups of 2-3 

at stem tips or in leaf axils. Flower stalks can be longer than those of OC.

REPRODUCTION: Both species spread by seed, rooting vines, and sprouting 

from root crowns. It is unknown how long seeds remain viable in the soil.

 

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

corridors, rocky slopes, and even partially shaded woodlands.

LOOK-ALIKES: Several native and exotic Clematis spp. occur in the Northwest. 

The yellow flowers and 5-7 leaflets help differentiate these two species from 

look-alikes, which typically have 

white or purple flowers and/or 

only 3 leaflets per leaf.

NOXIOUS WEED LISTINGS:

OC: CO (B), WA (A, Prohib.); YC: AB

NOTES: Both species are frequent 

escapees from the horticulture industry. 

The juice of freshly crushed foliage may 

cause blisters. Oriental clematis Yellow clematis
Yellow-flowered brooms

104 New Invaders of the Northwest YELLOW FLOWERS Trait

French

Genista monspessulana

Portuguese

Cytisus striatus

Spanish

Spartium junceum

Preferred

Habitat

Disturbed, open; 

High pH soil; Mesic

Disturbed, open; Mesic 

habitat

Disturbed, open areas; 

Dry conditions

Height 3-10’ (1-3 m) 3-10’ (1-3 m) 5-15’ (11⁄2-41⁄2 m)

Leaves

3-parted; Leaflets 

1⁄3-1⁄2” (1-11⁄4 cm); 

Hairy; Numerous; 

On plant year-round 

Single to 3-parted; 

Leaflets 1⁄3-1⁄2” (1-11⁄4 

cm); Smooth above, 

hairy below; Sparse; 

Deciduous early

Single; 1⁄2-1” (11⁄4-21⁄2 

cm); Oval, smoothmargined; Deciduous 

early

Stems

Young: slender, green, 

ridged; Mature: 

brown, round

Young: slender, green; 

Mature: brown, woody

Young: slender, green, 

round, rush-like; 

Mature: woody, round

Flowers

Yellow; ≤1⁄2” (11⁄4 

cm); Clusters 4-10 at 

branch ends; Spring/

summer

Pale yellow; ≤1” (21⁄2 

cm); Clusters 1-2 

in leaf axils; Spring/

summer

Yellow; ≤1” (21⁄2 cm); 

Clusters of several at 

current-year branch 

ends; Summer into fall

Pods

1⁄2-1” (11⁄4-21⁄2 cm); 

Dense hair

1⁄2-11⁄2” (11⁄4-4 cm); 

Inflated; Dense hair

2-4” (5-10 cm); Slightly 

flattened; Dense hair

French broom: a) plant (Philipp Weigell), b) flowers (Calibas), c) seed pods and leaves (Xemenendura)

c

b

a
Family Fabaceae

New Invaders of the Northwest 105

Portuguese broom: d) plant, e) stems and flowers (d,e ©2011 Vernon Smith, f) seed pods and leaves 

(© 2011 Zoya Akulova)

Spanish broom: g) plant, h) flowers (g,h Jennifer Andreas, Washington State University Extension), 

i) mature seed pod (Eugene Zelenko) 

i

h

g

f

e

d
Yellow-flowered brooms (continued)

106 New Invaders of the Northwest YELLOW FLOWERS NAMES: French broom, Genista monspessulana (L.) L.A.S. Johnson (IB)

 Portuguese broom, Cytisus striatus (Hill) Rothm. (PB)

 Spanish broom, Spartium junceum Curtis (SB)

SYNONYMS: FB: canary broom, cape broom, Cytisus monspessulanus L.; PB:

hairy-fruit broom, striated broom, Genista striata Hill; SB: weaver’s broom, genet

ORIGIN: Mediterranean (all species)

GROWTH TRAITS:

French broom (FB): Upright, perennial shrub growing 3-10’ tall (1-3 m) from a 

taproot. Stems are ridged and green when young, becoming rounded and brown 

at maturity. Leaves are 3-parted and numerous on stems. Leaflets are 1⁄3-1⁄2” long 

(1-11⁄4 cm) and oval-shaped with the tip wider than the base. Leaves remain on 

the plant year-round. Young stems and leaves are covered in silvery hairs. Yellow 

flowers occur in clusters of 4-10 at the ends of branches. Flowers are pea-like 

(having a banner, wing and keel, typical of the pea family), are up to 1⁄2” long 

(11⁄4 cm), and bloom in spring and early summer. The fruit is a pod 1⁄2-1” long 

(11⁄4-21⁄2 cm), covered in dense silky hairs, and dark brown or black at maturity.

Portuguese broom (PB): Upright, long-lived perennial shrub growing 3-10’ tall 

(1-3 m) from a taproot. Young plants are dominated by a leading stem; plants 

become more branched and broaden with age. Stems are slender and green when 

young, becoming brown and woody at maturity. Stems are only sparsely covered 

with leaves. Leaves are single to 3-parted. Leaflets are 1⁄3-1⁄2” long (1-11⁄4 cm) 

and smooth above while hairy beneath. Leaves fall off early in the season or in 

times of stress. Pale yellow flowers occur in clusters of 1-2 in leaf and stem axils. 

Flowers are pea-like (having a banner, wing and keel, typical of the pea family), 

are up to 1” long (21⁄2 cm), and bloom in spring and early summer. The fruit is 

a pod 1⁄2-11⁄2” long (11⁄4-4 cm), inflated, and densely covered in long white hairs. 

Spanish broom (SB): Upright, perennial shrub growing 5-15’ tall (11⁄2-41⁄2 m) from 

a taproot. Slender stems are erect with few branches, round in cross-section, and 

rush-like. Stems are green when young, maturing into woody branches with 

bark. Leaves are 1⁄2-1” long (11⁄4-21⁄2 cm), oval, and smooth-margined. Leaves 

remain on the plant for 4 months or less, and are typically gone by flowering 

time. Several yellow flowers occur in long clusters at tips of current-year shoots. 

Flowers are pea-like (having a banner, wing and keel, typical of the pea family), 

are up to 1” long (21⁄2 cm), and bloom throughout summer and into fall. The 

fruit is a pod 2-4” long (5-10 cm) that is slightly flattened and densely covered 

in long hairs. Fruits are light green initially, turning dark brown with age. 
Family Fabaceae

New Invaders of the Northwest 107

REPRODUCTION: All three species reproduce by seed only. Seeds of most 

broom species may remain viable in the soil for at least five years, though many 

are viable longer.

 

HABITAT: All three species capitalize on disturbance for establishment and can 

be found in open areas with full sun such as roadsides, trails, vacant lots, and 

disturbed hillsides. SB prefers drier sites, while FB can be found in more moist 

conditions along riverbanks and in meadows or moist hillsides. All three are 

more common in coastal regions than the interior. Unlike other brooms, FB

grows fairly well in alkaline soils.

LOOK-ALIKES: These three brooms resemble 

Scotch broom (Cytisus scoparius), another invasive, 

yellow-flowered broom that is widespread in the 

Northwest. Scotch broom can be differentiated 

by its combination of: pods 0.8-2” long (2-5 cm) 

with hairs only along the pod seams, 3-parted and 

single leaves that are deciduous early, and young 

stems that are star-shaped in cross-section. To 

differentiate these three species from each other, 

refer to the comparison table three pages previous.

NOXIOUS WEED LISTINGS: FB: OR (B), WA 

(A, Prohibited); PB: OR (B); SB: CA, OR (B), WA 

(A, Prohibited)

NOTES: All three species can re-sprout from the root crown following cutting. 

Stems of all three species are used in photosynthesis.

Look-alike: Scotch broom 

(Jennifer Andreas, Washington 

State University Extension)

French broom Portuguese broom Spanish broom
Glossary

108 New Invaders of the Northwest GLOSSARY 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.

basal Located at the base of a plant or plant part

biennial A plant that lives two years, typically flowering and 

fruiting its second year

bolting Plant stage at which the flower stalk begins to grow

bract A small, leaf-like structure below a flower

capitulum (pl. capitula) Seed head or flower head of a plant in the sunflower family

compound leaf A leaf consisting of two or more leaflets borne on the 

same leaf stalk

deciduous Sheds its leaves annually

density Number of individuals per unit area

divided Synonym for compound leaf

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
New Invaders of the Northwest 109

flower head A special type of inflorescence consisting of numerous 

florets that actually look like one flower

forb Herbaceous plant (does not have woody stems)

herbaceous Does not have woody stems

hyperaccumulator A plant capable of growing in soils with very high 

concentrations of metals, absorbing these metals 

through their roots, and concentrating extremely 

high levels of metals 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 ofen 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 a the leaf stalk

ligule A thin outgrowth at the junction of leaf and leafstalk 

of many grasses and sedges

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

nontarget effect When control efforts affect a species other than the 

species they were enacted to control (can be positive 

or negative)

opposite Where leaves appear in twos at stem nodes, on 

opposite sides of the stem
110 New Invaders of the Northwest GLOSSARY ovate Shaped like an egg, with the base wider than the tip

pappus A tuft of hairs, scales, or bristles at the base of an 

achene in flowers of the sunflower family

perennial A plant that lives for more than two years

petiole Leaf stalk that usually attaches it 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

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

scarification Cutting the seed coat using abrasion, thermal stress, 

or chemicals to encourage germination

seed head Synonym for capitulum of a plant in the sunflower 

family. Consists of a receptacle and florets

senescence Final stage in a plant’s life cycle

sepal A small, (typically) green petal-like structure beneath 

petals that protect petals in bud and support petals 

during open flowering

spadix Inflorescence with several tiny flowers clustered on a 

narrow, fleshy stem

spathe Leaf-like curved bract surrounding a spadix

stamen The pollen-producing reproductive organ of a flower

stolon Stem which grows at the soil surface or just below 

ground that forms adventitious roots at the nodes, 

and new plants from the buds (also called runner)
New Invaders of the Northwest 111

succulent Plants having some parts that are more than normally 

thickened and fleshy, usually to retain water in arid 

climates or soil conditions

taxonomy The classification of organisms in an ordered system 

that indicates natural relationships. The science, 

laws, or principles of classification; systematics

toothed Leaf margin that is regularly incised, such as for a saw

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 the 

winter, and produces seed and dies in the following 

season
Selected References

112 New Invaders of the Northwest REFERENCES Aikio, S., R.P. Duncan and P.E. Hulme. 2010. Lag-phases in alien plant invasions: 

separating the facts from the artefacts. Oikos 119:370–378.

CABI. 2014. Invasive Species Compendium, CABI Publishing, Wallingford, UK.

Dietz, H., A. Köhler and I. Ullmann. 2002. Regeneration growth of the invasive 

clonal forb Rorippa austriaca (Brassicaceae) in relation to fertilization and 

interspecific competition. Plant Ecology 158:2 172-181.

DiTomaso, J.M., G.B. Kyser et al. 2013. Weed Control in Natural Areas in the 

Western United States. Weed Research and Information Center, University of 

California. 544 pp.

Encycloweedia. 2014. Integrated Pest Control, California Department of Food and 

Agriculture. University of California, Davis, Cooperative Extension Service, 

Weed Science Program. Available: http://www.cdfa.ca.gov/plant/ipc/weedinfo/

winfo_table-sciname.html. [2014, June 21].

French, K. 2010. Alyssum murale & Alyssum corsicum, Illinois Valley, O’Brien & 

Kerby, Oregon. Josephine County. Oregon Department of Agriculture. 17 pp.

Gucker, Corey L. 2009. Coronilla varia. In: Fire Effects Information System, 

[Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain 

Research Station, Fire Sciences Laboratory (Producer). Available: http://www.

fs.fed.us/database/feis/ [2014, July 5]. 

Jepson Flora Project (Eds.: Bruce G. Baldwin, David J. Keil, Staci Markos, Brent 

D. Mishler, Robert Patterson, Thomas J. Rosatti, Dieter H. Wilken). 2013. 

Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on Jun 11 2014.

Kostel G. 2009. Thymelaea passerina (Thymelaeaceae) in South Dakota. J. Bot. Res. 

Inst. Texas 3(2): 901-903.

Munger, G.T. 2002. Pueraria montana var. lobata. In: Fire Effects Information 

System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky 

Mountain Research Station, Fire Sciences Laboratory (Producer). Available: 

http://www.fs.fed.us/database/feis/ [2014, June 25].

Nuzzo, V. 2000. Alliaria petiolata (Alliaria officinalis), Garlic Mustard. In: (J.M. 

Randall, ed.) Element Stewardship Abstract. The Nature Conservancy. 

Arlington, Virginia. 19 pp.

ODA. 2014. Noxious Weed Control Program. [Online]. Oregon Department 

of Agriculture. Available: http://www.oregon.gov/ODA/PLANT/WEEDS/

Pages/statelist2.aspx [2014, June 1].

Rosenthal, D.M., A.P. Ramakrishnan, and M.B. Cruzan. 2008. Evidence for 

multiple sources of invasion and intraspecific hybridization in Brachypodium 
New Invaders of the Northwest 113

sylvaticum (Hudson) Beauv. in North America. Molecular ecology 17(21): 

4657-4669. 

Spencer, N.R. and T. Sankaran.1985. Prospects for biological control of velvetleaf 

(Abutilon theophrasti). In E.S. Delfosse, Ed. Proceedings of the VI International 

Symposium on Biological Control of Weeds. 19-25 August 1984, Vancouver, 

Canada; Agriculture Canada. pp. 837-842.

USDA, ARS, National Genetic Resources Program. 2014. Germplasm Resources 

Information Network - (GRIN) [Online Database]. National Germplasm 

Resources Laboratory, Beltsville, Maryland. Available: http://www.ars-grin.

gov/cgi-bin/npgs/html/taxon.pl?403159 [2014].

Wang, W. T., 2006: A revision of Clematis sect. Meclatis (Ranunculaceae). Acta 

Phytotaxonomica Sinica 44: 401–436.

Washington State Noxious Weed Control Board. 2011. Fact Sheet: Italian arum, 

Arum italicum. 7 pp.

WNWCB. 2014. [Online]. Washington State Noxious Weed Control Board. 

Available: http://www.nwcb.wa.gov. [2014, June 1].

Zheng, H.;, Y. Wu, Y., J. Ding, D. Binion, W. Fu, and R. Reardon. 2004. Invasive 

Plants of Asian Origin Established in the United States and Their Natural 

Enemies. Volume 1. United States Department of Agriculture, Forest Service. 

FHTET-2004-05. Morgantown, WV. 147 pp.

Zouhar, Kris. 2005. Fire Effects Information System, [Online]. U.S. Department 

of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences 

Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2014, 

June 20].

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
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