Nonnative Invasive Plants of Pacific Coast Forests i

A Field Guide for Identification

DEP

Andrew N. Gray, Katie Barndt, and Sarah H. Reichard AR TMENT OF AGRICULT URE

United States

Department 

of Agriculture

Forest Service

Pacific Northwest Research Station

General Technical Report PNW-GTR-817

May 2011
Authors

Andrew N. Gray is a research ecologist, U.S. Department of Agriculture, 

Forest Service, Pacific Northwest Research Station, 3200 SW Jefferson 

Way, Corvallis, OR 97331. Katie Barndt was a Ph.D. student, and Sarah H. 

Reichard is an associate professor, School of Forest Resources, University 

of Washington, Seattle, WA 98195. Barndt is currently an instructor at North 

Seattle Community College, Seattle, WA 98103.

Front cover: (upper left) Herb-robert; (upper right) spotted knapweed; 

(lower left) medusahead; (lower right) Himalayan blackberry.

Back cover: (upper left) Tree of heaven; (upper right) squarrose knapweed; 

(lower left) Dyer’s woad; (lower right) Jubata grass.

Abstract

Gray, Andrew N.; Barndt, Katie; Reichard, Sarah H. 2011. Nonnative 

invasive plants of Pacific coast forests: a field guide for identification. 

Gen. Tech. Rep. PNW-GTR-817. Portland, OR: U.S. Department of 

Agriculture, Forest Service, Pacific Northwest Research Station. 91 p.

Nonnative plants affect the composition and function of natural and managed ecosystems and have large economic effects through lost or degraded 

land use and eradication costs. In spite of their importance, very little 

comprehensive information on the abundance, distribution, and impact of 

nonnative invasive plants is available. The objective of this study was to 

prioritize a list of nonnative invasive plants affecting forest lands in the 

Pacific coastal states of California, Oregon, and Washington, and provide 

enough detail in nontechnical language and photos of different stages of 

plant development to allow reliable identification in the field. Information 

was synthesized from a variety of national, regional, and state lists, 

assessments, and botanical guides. The final list was designed to capture 

species believed to be most prevalent or problematic and to be used for 

strategic forest inventories like the Forest Inventory and Analysis Program. 

Identification of the several hundred nonnative invasive species present in 

the region requires substantial taxonomic experience; a prioritized short list 

of species with practical identification tips can be a good place for novice 

botanists and large-scale monitoring efforts to start.

Keywords: invasive species, nonnative plants.

The Forest Service of the U.S. Department of Agriculture is dedicated to the principle 

of multiple use management of the Nation’s forest resources for sustained yields of 

wood, water, forage, wildlife, and recreation. Through forestry research, cooperation 

with the States and private forest owners, and management of the National Forests 

and National Grasslands, it strives—as directed by Congress—to provide increasingly 

greater service to a growing Nation.

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

and activities on the basis of race, color, national origin, age, disability, and where 

applicable, sex, marital status, familial status, parental status, religion, sexual 

orientation, genetic information, political beliefs, reprisal, or because all or part of an 

individual’s income is derived from any public assistance program. (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, 

1400 Independence Avenue, SW, Washington, DC 20250-9410 or call (800) 795-

3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and 

employer.
2

Introduction

2Methods

4Species Descriptions

5Acknowledgments

6

Trees and Shrubs

6Tree of heaven

8Brooms

1

0

Gorse

1

2

Himalayan blackberry

1

4

Cutleaf blackberry

16English holly

18English ivy

20Old-man’s-beard

22Cotoneasters

24Butterfly bush

26Tamarisk

2

8 Forbs

2

8

Knotweeds

3

1

Composite (Asteraceae) 

 Differentiation

3

2

Knapweeds

3

6

Starthistles

3

8

Thistles

4

2

Rush skeletonweed

4

4

Hawkweeds

4

6

Oxeye daisy

4

8

Purple loosestrife

50Dalmatian toadflax

5

2

Leafy spurge

54Houndstongue

56Perennial pepperweed

5

8

Hoary cress and hairy whitetop

60Dyer’s woad

62Garlic mustard

6

4

Common St. Johnswort

66Sulfur cinquefoil

6

8

Herb-robert

70

Policeman’s helmet

7

2

Grasses

72Medusahead

7

4

Cheatgrass

7

6

Slender false brome

7

8

Jubata grass

80

Giant reed

82Bulbous bluegrass

84Glossary

90

Metric Equivalents

9

0

References

Contents

Yellow starthistle, Centaurea solstitialis L.

TREES and SHRUBS FORBS GRASSES

Institute for Applied Ecology
2

Introduction

Nonnative plants affect the composition and 

function of natural and managed ecosystems 

and have large economic effects through lost 

or degraded land use and eradication costs 

(Mooney and Hobbs 2000, Pimentel et al. 2005, 

Vitousek et al. 1996). In response to these 

threats, many efforts to assess ecosystem health 

and sustainable management focus on the need 

to know how abundant invasive species are 

(Heinz Center 2002, Journal of Forestry 1995, 

National Research Council 2000). In spite of 

their importance, very little comprehensive 

information on the abundance, distribution, and 

impact of nonnative invasive plants is available 

(Blossey 1999). As a result, it is currently not 

possible to provide a comprehensive assessment 

of the abundance and impacts of nonnative invasive plants in the United States (Heinz Center 

2002, National Research Council 2000).

The objective of this report is to provide a 

prioritized short list of the nonnative invasive 

plants having the greatest impact on forested 

lands in the Pacific coastal states of California, 

Oregon, and Washington. To be useful in 

regional resource monitoring, the list emphasizes species that are recognizable for most 

of the year. In addition, we hoped to provide 

enough detail in nontechnical language and 

photos to allow reliable identification of these 

species in the field by people without specialized 

botanical training. This work was inspired by 

a useful lay-oriented publication of nonnative 

invasive plants of southern forests (Miller 2003). 

The list was designed to be available for use in a 

strategic forest inventory, such as that conducted 

on all forest lands in the region by the Forest 

Inventory and Analysis (FIA) Program of the 

U.S. Department of Agriculture (USDA) Forest 

Service Pacific Northwest Research Station. 

Although identification and monitoring of all 

nonnative invasive species in the region would 

be ideal, the sheer number of species—4,139 

in the United States (USDA NRCS 2009) and 

several hundreds in any one region—requires 

fieldwork by experienced taxonomists (Gray and 

Azuma 2005). A prioritized short list of species 

can be a good place for novice botanists and 

native plant managers to start.

Methods

The first step to create a priority list of nonnative invasive plants was to compile invasive 

plant lists from a variety of public and private 

organizations in the region. Because each list 

was created with a specific process or set of 

criteria in mind (e.g., some focus on nonforest 

agricultural weeds), the goal of this step was to 

be as inclusive as possible.

Each of the states’ governments maintains 

noxious weed lists, and these were downloaded 

from agency Web sites (California Department 

of Food and Agriculture 2008, Oregon Department of Agriculture 2008, Washington State 

Noxious Weed Control Board 2008). A short 

list of species monitored by FIA on Pacific 

Southwest Region (Region 5) national forests 

in California was included (USDA Forest 

Service 2006), as well as a draft list for Pacific 

Northwest Region (Region 6) national forests 

in Oregon and Washington recommended by an 

invasive plants coordinator (Linda Mazzu 2008. 

Personal communication. Regional botanist, 

Region 6). Lists from multiagency invasive 

plant councils in California and Oregon were 

also included (California Invasive Plant Council 

2006, Oregon Invasive Species Council 2008). A 

national list produced by a conservation organization was also available (Morse et al. 2004), 

as well as an academic publication on the worst 

invaders of the Pacific Northwest (Boersma et 

al. 2006). The lists were combined into a single 

list of 421 species using the nomenclature in the 

PLANTS database, a nationally standardized 

taxonomic reference (USDA NRCS 2009).

In addition, a list of nonnative plants 

recorded on FIA plots was compiled. There were 

201 plots in Oregon and Washington measured 

with the national FIA vegetation indicator 

protocol (Schulz 2003) on a pilot basis; intensive 

measurements of all species were taken by 

experienced botanists during the summer growing season, and specimens of unknown plants 

were identified by Oregon State University 

Herbarium staff. Nonnative species recorded 
3

according to the regional understory vegetation 

protocol were also included. For this protocol, 

crews recorded the three most abundant species 

per life form (tree seedlings, shrubs, forbs, and 

graminoids) and any additional plants found at 

≥3 percent cover on the plot. Expertise differed 

among crews, and not all plants were identifiable 

when plots were measured (April–October), so 

many vegetation records were of genus or life 

form, particularly for forbs and graminoids. 

There were 48 species that were nonnative, were 

recorded on more than one vegetation indicator 

plot or more than five regional vegetation plots, 

and were not on any of the other invasive lists; 

these were added to the species list for a total of 

469 species that were ranked for priority.

The species were ranked for priority by 

using a variety of criteria:

• Nativity: whether that species was 

entirely or partially nonnative to the 

United States.

• Habitat: likelihood that species occurred 

on forest land.

• Invasiveness: an index of the ecological 

impact, invasive potential, ecological 

amplitude, and distribution of a species.

• Distribution: degree to which occurrence is widespread or in many vegetation types.

• Identifiability: ease of identification 

based on phenology and growth habit.

The PLANTS database (USDA NRCS 

2009) was used to determine which species were 

nonnative to the United States (some of the state 

noxious lists included native agricultural weeds), 

or which were listed as having both native 

and nonnative populations in the country. For 

example, common yarrow (Achillea millefolium 

L.) in the United States consists of native and 

introduced populations that are not distinguishable in the field, and probably have hybridized. 

This species is abundant in disturbed western 

forest lands, but it is unknown if this invasiveness is a trait common to the native genotypes or 

a result of the spread of the introduced genotypes (Hitchcock et al. 1969, Hurteau and Briggs 

2003). Only species listed as fully nonnative 

were retained in the final list.

Only species that were likely to be found 

in forest habitats were included. Identifying 

species that occurred in forest habitats consisted 

of searching a variety of written materials for 

the words “forest,” “woodland,” or “riparian.” 

In addition, species found on the national forest 

lists or that met the minimum frequency on 

FIA plots were included as forest species. After 

applying the nativity and habitat criteria, 245 

species were left for further ranking. Habitat 

points were also assigned, with codes of 4 for 

forest, 3 for woodland, 2 for riparian, and 1 

for other.

The invasiveness ratings are focused on 

impacts to nonagricultural plant communities 

and were based on formalized criteria applied by 

experts (Morse et al. 2004). Additional invasiveness criteria can be used (e.g., abundance, cost 

of control), and we attempted to capture them 

in the other rating items. Conservation rankings 

were available in three of the lists examined. 

Invasiveness points were assigned to each species ranging from 5 (for species ranked "high" 

on any invasive list) to 1 (species ranked "low" 

or "insignificant" on any invasive list).

The distribution criteria were based on 

information provided in the lists that were 

examined, and distribution points were assigned 

to each species ranging from 5 (widespread) 

to 1 (limited or not present). Frequencies on 

FIA plots were used for species that lacked 

information.

Identification points were added to the 

spreadsheet to roughly describe the ability of a 

nonbotanist with modest training in identifying 

species. Trees and evergreen shrubs were ranked 

highly, deciduous shrubs lower, forbs next, forbs 

in the family Asteraceae lower still, and grasses 

lowest. Identifiability is related to the number of 

similar species and the length of time during the 

year in which the plants have diagnostic parts 

(e.g., flowers, fruits, or leaves).
4

The somewhat rough rankings of habitat, 

invasiveness, distribution, and identification 

points were added up and species grouped into 

four lists for experts to evaluate (readers interested in seeing the full list may contact the first 

author). The 25 nongraminoid species with the 

highest total points were placed in a preliminary 

“monitor” list, and 50 nongraminoid species 

with the next highest points and 20 graminoid 

species with the highest points were placed in 

“supplemental" lists. Experts from different 

regions within the three states were asked to 

indicate for each species whether it occurred in 

their region, what the priority for monitoring 

was, whether it should be moved to the monitor 

list or taken off, and why. Fourteen individuals 

responded with recommendations and many 

helpful comments, and covered the geographic 

range, although responses from eastern Oregon 

and southern California were underrepresented.

Survey responses were given points for 

species recommended for monitoring based 

on the priority they assigned: 3 = high, 2 = 

medium, 1 = low, 0 = no list. Because responses 

differed in the number of species recommended 

for monitoring, species scores were relativized 

so that the total for each respondent was 100. 

Scores were then summed for all responses, 

and by region. The species ranked in the top 40 

across all regions, plus those with high scores in 

one or more regions, were included in the final 

list. Initial regions were western Oregon and 

Washington, eastern Oregon and Washington, 

Klamath region (southwest Oregon and northwest California), and remaining portions of 

California. Regions were simplified into western 

Oregon and Washington, eastern Oregon and 

Washington, and California based on the overlap 

in species ranking in the initial regions.

The final list included 1 tree, 16 shrubs, 34 

forbs, and 6 grasses, for a total of 57 species. 

However, the total for any one region did not 

exceed 45 species. In addition, many of the 

species were treated as “groups” of closelyrelated species, in which case the total number 

of groups per region was either 25 or 26.

Species Descriptions 

The species descriptions were written to provide basic diagnostic information about stems, 

leaves, flowers, and fruit for each species. In 

addition, information on seasonality and distinguishing features from similar species is provided. Many species descriptions were adapted 

from DiTomaso and Healy (2007), Wisehart et 

al. (2008), and Miller (2003), with additional 

guidance from regional floras. Readers seeking 

greater detail and information on additional 

species in this region are encouraged to consult 

DiTomaso and Healy (2007). In addition to the 

descriptions, photos are provided illustrating 

each species and diagnostic plant parts to aid in 

identification. Many photos were taken by Katie 

Barndt and the Institute for Applied Ecology 

(Corvallis, Oregon), and many others were 

graciously provided by other photographers (see 

credits). In addition, county distribution maps 

for each state created by the PLANTS database 

(USDA NRCS 2009) are provided.

Descriptions are written to minimize the 

use of botanical terms for ease of use, but the 

botanical terms are more succinct and precise 

and are sometimes used; many are included in 

parentheses after common phrases and defined 

in the glossary to aid in identification. Key 

recognition attributes are highlighted with 

bold to facilitate rapid plant identification. 

Nomenclature for all species follows USDA 

NRCS (2009). Metric units are provided in some 

cases where the English units are too small 

to appear on common rulers (e.g., 0.05 inch). 

We have not included control methods in this 

publication, as they can differ depending on the 

regulatory environment and management goals 

for an area, and can become quickly out of date 

with new information. Readers desiring information on controlling specific plants may refer 

to DiTomaso and Healy (2007), Boersma et al. 

(2006), Miller (2003), and resources available on 

the Internet (e.g., http://www.invasive.org/, http://

www.pnw-ipc.org/, http://www.cal-ipc.org/).
5

Acknowledgments

Scott Sundberg and Katie Mitchell of the 

Oregon State University Herbarium identified 

plant voucher specimens. Steve Acker, Jim 

Belsher-Howe, Beth Brenneman, Mignonne 

Bivin, Robin Dobson, Chuck Fairchild, 

Timothy Harrington, Jennifer Hutchinson, 

Laurie Kurth, Robin Lesher, Terry Lillybridge, 

Jennifer Lippert, Linda Mazzu, Cindy McCain, 

Carol Ogilvie, Regina Rochefort, Catharine 

Thompson, Peter Warner, Andrea Williams, and 

Andrea Woodward provided rankings and valu-

able comments on the initial species list, which 

helped us prioritize species for the final list. 

Tom Kaye and Andrea Thorpe of the Applied 

Ecology Institute coordinated the collection of 

many of the photographs used in this publica-

tion. Many other photographers freely provided 

their photos; each photo is identified with the 

name of the photographer. Joe DiTomaso, 

Mandy Tu, and Timothy Harrington provided 

helpful comments on an earlier version of this 

manuscript.
6

TREES and SHRUBS

Tree of heaven

AIAL

Katie BarndtKatie BarndtKatie Barndt

Katie BarndtKatie Barndt

James H. Miller, USDA Forest Service, Bugwood.org

Katie Barndt
7

TREES and SHRUBS

Ailanthus altissima (P. Mill.) Swingle AIAL

Synonyms: Ailanthus, copal tree, varnish tree, Chinese sumac, Ailanthus glandulosa 

Desf., Toxicodendron altissima Mill.

Plant: Deciduous, fast-growing tree with a single trunk 20–60 (to 100) feet tall and 

up to 3 feet in diameter, large compound leaves and circular glands under lobes 

at base of leaflets, gray bark, and distinctive leaf scars. Large flower clusters of 

flattened winged fruit persist on female trees. The creeping roots readily sprout new 

stems, often producing thickets. Family: Simaroubaceae.

Stem: Young bark is smooth and light grayish brown, older bark has diamond-shaped 

fissures. Twigs range from green to reddish and velvety when young to light brown, 

smooth, and stout when old, with many light dots (lenticels). Leaf scars are heart 

shaped.

Leaves: Leaves are alternate, compound with leaflets on either side of a central axis 

(pinnate), deciduous, 1–3 feet long, with 10–41 leaflets per leaf, and usually with a 

leaflet at the tip. Leaflets are not always directly opposite. Leaflet blades are lance 

shaped (lanceolate) to egg shaped (ovate), narrowing toward the tip, with 2–4 lobes or 

blunt teeth at the base; each lobe typically has a large, round, green gland on the underside. Leaflets are 2–7 inches long and 1–2 inches wide, with leaflet stalks (petioles) 

1⁄4 –3⁄4 inch long. Leaf margins are smooth-edged (entire) except for the lobes. The upper leaf surface is dark green with light-green veins when mature, reddish and covered 

with very short, velvety hairs when young; the lower leaf surface is whitish green. 

Leaves smell “skunky” when crushed.

Flowers: Blooms April to June, with large clusters of flowers up to 20 inches long at 

branch tips. The flowers are small, about 1⁄4 inch across, and greenish yellow, with 

5 petals and 5 sepals. Male flowers have 10 stamens, and female flowers have 2–5 

pistils. Male and female flowers occur on separate trees (dioecious).

Fruit and seeds: Fruit remains on trees from July to February, in large clusters (up to 

12 inches across) of flattened, twisted, winged fruit, each with a single seed. The 

fruit is of uniform width throughout its length (linear), 1 inch long, 1⁄2 inch wide, green 

when young, and ripening to a tan or reddish brown.

Habitat: Riparian areas, grassland, oak woodland, disturbed areas and open fields, 

below 5,000 feet in elevation. Trees are shade and flood tolerant.

Similar-looking plants: Other plants with large pinnately compound leaves include 

southern and northern California walnut (Juglans californica S. Watson and J. hindsii 

(Jeps.) Jeps. ex R.E. Sm., respectively), which have leaflets with finely sharp-toothed 

(serrated) margins without blunt teeth at the base and without glands under teeth, and 

fruit is a walnut; and sumacs (Rhus spp.), which are shrubby, have serrated leaves, 

lack glands under leaflets, and fruits are red, fuzzy, and fleshy with a single hard seed 

(drupe).

Tree of heaven

Katie Barndt

Katie Barndt
8

TREES and SHRUBS

CYSC4 GEMO2 SPJU2

Above: Scotch broom (CYSC4). 

Below: French broom (GEMO2).

Brooms

Institute for Applied EcologyInstitute for Applied EcologyInstitute for Applied EcologyInstitute for Applied Ecology

© Mandy Tu/The Nature Conservancy Alfred Brousseau
9

TREES and SHRUBS

1.Scotch broom, Cytisus scoparius (L.) Link CYSC4

2.French broom, Genista monspessulana (L.) L. Johnson GEMO2

3.Spanish broom, Spartium junceum L.SPJU2

Synonyms: (1) English broom, common broom, Scot's broom, Sarothamnus scoparius 

(L.) Wimm ex Koch, Spartium scoparium L.; (2) Cape broom, Montpellier broom, 

Cytisus monspessulanus L., Teline monspessulana (L.) K. Koch; (3) weaver’s broom, 

Genista juncea Lam.

Plant: Large, multibranching, woody shrubs up to 10 feet tall with erect green stems, 

yellow “pea-flowers” and legumes (pods). Family: Fabaceae (pea, legume).

Stem: Stems of Scotch broom are dark green and strongly angled (approximately star 

shaped in cross section) with 5 ridges, with new twigs covered in wavy hairs, becoming smooth with age, and older branches turning brown and losing ridges. Stems 

of French broom are round, covered in silky hairs, and have 8–10 ridges. Stems of 

Spanish broom are bright green and round, and almost smooth with fine ridges and 

almost leafless.

Leaves: Leaves of Scotch and French broom are compound with 3 leaflets that are 

each 1⁄4–3⁄4 inch long and are nearly rectangular (oblong) to egg shaped (obovate), but 

are deciduous in Scotch broom and evergreen in French broom. Leaves of Spanish 

broom are single (simple), deciduous, narrow and uniform (linear) to lance shaped 

(lanceolate), and 1⁄2–11⁄4 inches long.

Flowers: Pea-like, usually bright yellow (pale yellow to maroon red in Scotch 

broom). Scotch broom blooms primarily in March to June; flowers are 1⁄2–1 inch long, 

have smooth outer whorls (sepals), and occur single or paired in the joints where 

leaves attach to stems (axils). French broom blooms March to May; flowers are about 

1⁄2 inch long, have hairy sepals, and occur in head-like clusters of 4 to 19 flowers at the 

ends of short shoots. Spanish broom blooms April to June; flowers are 3⁄4–1 inch long, 

have smooth sepals, and occur in open clumps at the end of leafless stems.

Fruit and seeds: Seed pods are brown (sometimes black in Scotch broom) at maturity. Scotch broom pods are 1–3 inches long and flattened, with long white hairs on 

the seam. French broom pods are 1⁄2–11⁄4 inches long, slightly flattened, and covered 

in hairs. Spanish broom pods are 1–4 inches long, slightly flattened, and covered in 

hairs.

Habitat: Open woodland, disturbed areas, grasslands, pasture, and rangeland. 

Scotch broom is found in winter-wet cooler conditions than the others.

Similar-looking plants: Gorse (Ulex europaeus L.) has bright yellow pea-like flowers 

but also has thorny stems, unlike the brooms. Portuguese broom (Cytisus striatus 

(Hill) Rothm.) is currently rare, and has a unique combination of 8–10 angled 

branches, flowers found singly or paired in leaf axils, and inflated pods covered 

with hairs.

Below: Spanish broom (SPJU2). 

Brooms

Institute for Applied Ecology

Katie Barndt

Katie Barndt

Katie Barndt
10

TREES and SHRUBS

ULEU

Gorse

Katie Barndt

Forest and Kim Starr, U.S. Geological Survey, Bugwood.org
11

TREES and SHRUBS

Ulex europaeus L. ULEU

Synonyms: Common gorse, furze, thorn broom, whin.

Plant: Large, multibranching evergreen woody shrub up to 10 feet tall with 

leaves modified into spines, yellow “pea-flowers” and legumes (pods). 

Often forms impenetrable thickets. Family: Fabaceae (pea, legume).

Stem: Stems are highly branched and interwoven; green, strongly angled, and 

hairy when young; turning brown and woody as they mature. Branches end in a 

thorn.

Leaves: Leaves are alternate, single (simple), and evergreen. Juvenile leaves 

are narrow and uniform (linear) to lance shaped (lanceolate), then modified into 

spines 2–7 inches long. 

Flowers: Blooms in spring (but can begin in November in warmer climates), 

with flowers occurring singly or in small clusters in the joints where leaves 

attach to stems (axils). Flowers are like a “pea-flower,” bright yellow to 

orange-yellow, 1⁄2–3⁄4 inch long.

Fruit and seeds: The dark brown legumes (pods) are <1 inch long, covered in 

hairs, egg shaped (ovoid) to nearly rectangular (oblong) and slightly flattened, 

and with 1–6 seeds.

Habitat: Open woodland, disturbed forests, scrub, pastures and well-drained 

sites, including sand dunes and coastal bluffs.

Similar-looking plants: Brooms have similar flowers but do not have spiny 

stems and leaves.

Gorse

Katie Barndt

Fred Hrusa

Fred Hrusa

Forest and Kim Starr, U.S. Geological Survey, Bugwood.org
12

TREES and SHRUBS

RUAR9

Himalayan blackberry

Institute for Applied Ecology

Katie BarndtKatie BarndtKatie Barndt

Institute for Applied Ecology
13

TREES and SHRUBS

Rubus armeniacus Focke RUAR9 (RUDI2)

Synonyms: Himalayaberry, Rubus discolor (Weihe & Nees)*, 

Rubus procerus auct. non P.J. Müll. ex Genev

*Older nomenclature used in NRCS PLANTS version from 2000.

Plant: Large evergreen shrub that forms dense thickets of long, arched, 

thick stems (canes), up to 10 feet tall or 23 feet long. Stems are covered with 

prickles. Leaves are 3- to 5-parted, flowers are white to pinkish white and 

“roselike” (5-petaled), and the fruit is a blackberry. Family: Rosaceae (rose).

Stem: Stems are thick, up to 3⁄4 inch diameter. First-year stems are hairy, with 

strong ridges and furrows, losing the hairs with age. Second-year stems bear 

flowers and are less strongly grooved. Stems are covered in thick-based, 

straight or curved thorns (prickles), up to 1⁄2 inch long.

Leaves: Leaves are alternate, compound, evergreen (or semievergreen). 

Leaves typically have 5 (7–9) leaflets on vegetative stems, 3–5 leaflets 

on floral stems. Leaflets are broad with some shallow lobes, 2–4 inches long 

and widest above the middle, narrowing in short curves to a tip (acuminate), 

and with coarsely toothed margins. Upper surfaces of leaves are dark green 

and hairless, and lower surfaces appear whitish with dense hairs. The leaf 

stem (petiole) is 2–31⁄2 inches long and has prickles.

Flowers: Flowers are arranged in a multibranched clump (panicle), and 

are white or pink, up to 1 inch across. Flowers have 5 egg shaped (obovate) 

petals about 1⁄2 inch long, and 5 green sepals. Stamens are abundant, in 

clusters of 5–20, and pistils are numerous. Flower stems (pedicels) have 

prickles. 

Fruit and seeds: Blackberry (aggregate of drupelets). Fruit is black, 

shiny and succulent at maturity, green to red and hard when immature, 

up to 3⁄4 inch long. 

Habitat: Found in disturbed moist open sites, riparian areas, marshes, oak, 

and other open woodlands.

Similar-looking plants: Cutleaf blackberry (R. laciniatus Willd.) has highly 

dissected leaves, and lower leaf surfaces are nearly green, not white. 

Whitebark raspberry (R. leucodermis Douglas ex Torr. & A. Gray) has firstyear stems that are rounded, not grooved, leaflets that are broadest below 

the middle, not above, and bright white leaf undersides. Other blackberries/

raspberries have 3 leaflets or leaves have smooth margins (entire), lack 

prickles, or are primarily trailing plants (no canes).

Himalayan blackberry

Institute for Applied Ecology
14

TREES and SHRUBS

Cutleaf blackberry

RULA

Institute for Applied Ecology

Pat Breen, Oregon State University

George W. Hartwell
15

TREES and SHRUBS

Rubus laciniatus Willd. RULA

Synonyms: Evergreen blackberry, cut-leaved blackberry, Rubus vulgaris 

Weihe & Nees. var. laciniatus (Willd.) Dippel.

Plant: Woody shrub with arching branches up to 10 feet tall with 3–5-parted leaves, 

whose leaflets are heavily dissected, giving a lacy appearance. Flowers are white 

to pinkish white and “roselike” (5-petaled), and the fruit is a blackberry. Family: 

Rosaceae (rose).

Stem: Stems thick, to 1⁄2 inch diameter, often deep reddish. First-year stems with 

strong ridges and furrows. Stems are covered in thick-based, usually curved thorns 

(prickles).

Leaves: Leaves are alternate, compound, evergreen (semievergreen). Leaves 

typically have 3–5 (7) leaflets, and are heavily dissected to doubly compound.

Leaflets are 3⁄4–3 inches long, and the margins are sharply toothed. Upper leaf 

surfaces are green and hairless, and lower surfaces appear green with some hairs. 

Leaf stems (petioles) are 1–5 inches long, and the leaf central axis has a backwardcurved prickle.

Flowers: Flowers are arranged in a multibranched clump (panicle) of few to many 

flowers and are white or pink. Flowers have 5 egg-shaped (obovate) petals about 1⁄4 

inch long, and 5 green sepals. Stamens are abundant, but pistils typically number 

fewer than 15. Flower stems (pedicels) have prickles.

Fruit and seeds: Blackberry (aggregate of drupelets). Fruit is black, shiny and 

succulent at maturity, green to red and hard when immature, to less than 3⁄4 inch 

long.

Habitat: Found in disturbed moist open sites, riparian areas, marshes, oak and 

other open woodlands.

Similar-looking plants: Himalayan blackberry (R. armeniacus Willd.) does not 

have highly dissected leaves, and the lower leaf surface is white with small hairs. 

Whitebark raspberry (R. leucodermis Douglas ex Torr. & A. Gray) also does not 

have highly dissected leaves, and has first-year stems that are rounded, not 

grooved. Other blackberries/raspberries have 3 leaflets or leaves are smoothmargined (entire), lack prickles, or are primarily trailing plants (no canes).

Cutleaf blackberry

Institute for Applied Ecology
16

TREES and SHRUBS

English holly

ILAQ80

Katie BarndtKatie Barndt

Katie Barndt

Katie Barndt

Frank Vincentz
17

TREES and SHRUBS

Ilex aquifolium L. ILAQ80

Synonyms: Christmas holly, common holly, European holly.

Plant: Large evergreen shrub or tree up to 80 feet tall, often pyramidal in shape, 

with thick, shiny green leaves, small white flowers and red berries. Family: 

Aquifoliaceae.

Stem: Plant is generally single-stemmed but can sprout into multistemmed thickets. 

Bark is smooth and green on young branches, turning gray with age.

Leaves: Leaves are alternate, single (simple), and evergreen. Leaf blades are egg 

shaped (ovate) to nearly rectangular (oblong), 1–3 inches long and 3⁄4–21⁄2 inches wide. 

Leaf margins are undulating and spiny-toothed, but leaves can also be smoothedged (entire) on the same plant. Spiny teeth are triangular, coarse, stiff, sharp, and 

usually number fewer than 20 per mature leaf. Leaf stems (petioles) are short. The 

upper surface of the leaf is shiny, dark green, thick and waxy, with no hairs, and the 

lower surface is dull green with no hairs.

Flowers: Flowers are fragrant and arranged in long branched clusters originating 

where the leaves attach to branches (axils), with male and female flowers on separate 

plants (dioecious). The flowers are small, 1⁄3 inch across, with 4 white petals fused at 

the base, 4 sepals also fused at the base, and 4 stamens on male flowers.

Fruit and seeds: Fruit is round, red, and berry-like (drupe) with persistent sepals, 

1⁄3 inch across, and with 4 (2–8) hard thick-walled seeds (nutlets).

Habitat: Coastal forests, woodlands, riparian areas. Very shade tolerant.

Similar-looking plants: Hollyleaf cherry (Prunus ilicifolia (Nutt. ex Hook. & Arn.) D. 

Dietr.) occurs in woodlands and chaparral in southern California, but leaves usually 

have more than 20 slender, weak spines per leaf and fruits are 1⁄2-1 inch across and 

resemble commercial cherries. Individual holly leaflets resemble barberry (Oregon 

grape; Mahonia spp.) but those are usually small shrubs with compound leaves and 

thin, nonglossy leaflets. 

English holly

Katie Barndt

Katie Barndt

Below: Hollyleaf cherry (Prunus ilicifolia

(Nutt. e Hook. & Arn.) D. Dietr.)

J.S. Peterson, USDA Natural 

Resources Conservation Service
18

TREES and SHRUBS

English ivy

Katie Barndt

HEHE

Andrew Gray

Katie BarndtKatie Barndt

Katie Barndt

Katie Barndt

Cape ivy (Delairea odorata Lem.).
19

TREES and SHRUBS

Hedera helix L. HEHE

Note: Hedera species hybridize, have many cultivars, and are often misclassified. 

Atlantic (Irish) and Algerian ivy (H. hibernica (G. Kirchn.) Bean and H. canariensis

(Willd.) Cout.) are lumped here with English ivy (most plants on the west coast are 

actually H. hibernica [Murai 1999, Zika and Alverson 2005]).

Plant: Woody, evergreen vine that grows in dense mounds on the ground or climbs 

up trees or buildings, attached with aerial rootlets, to 100 feet high. Juvenile plants 

have lobed, white-veined leaves, whereas mature plants have unlobed leaves, are 

erect, and bear flowers and fruit. Family: Araliaceae.

Stem: Stems are woody, with thick bases on older plants. Juvenile form has aerial 

rootlets that can cling to tree bark, fences, and buildings.

Leaves: Leaves are alternate, single (simple), evergreen, and thick and leathery; 

upper surfaces are often glossy. Juvenile leaf blades are 3–5 lobed, 11⁄2–4 inches 

long and as wide. Lobes range from shallow to deep, with tip of lobes ranging from 

rounded to strongly narrowed toward the tip. Leaves are usually dark green, but 

can be blue green to light green, typically with light-colored veins on juvenile leaves. 

Mature leaves are egg shaped (ovate) to diamond shaped with less prominent veins 

on the upper surface. Leaf stems (petioles) are green and as long as the leaf blades.

Flowers: Plants flower in the fall and ripen in spring. Flowers are only found on 

mature plants exposed to moderate or high light. Flowers are in round clusters at 

the ends of stems, on stalks rising from a common point (umbel). Flowers are small, 

0.2–0.3 inch wide and greenish white or greenish yellow, with 5 petals, 5 sepals fused 

at the base, 5 stamens alternating with the petals, and a solitary, 5-lobed stigma.

Fruit and seeds: Fruit is round and berry-like (drupe), green when immature, and 

fleshy dark blue, purplish, or black when ripe. Fruit is 1⁄4–1⁄3 inch wide, with 2–5 seeds.

Habitat: Forests, woodlands, riparian, and disturbed areas. Very shade tolerant.

Similar-looking plants: Cape ivy (Delairea odorata Lem.) occurs in coastal California 

and southwest Oregon. It does not have a woody base, leaves have a deep cleft in 

the base that give them a kidney shape, and flowers are yellow and daisylike. Grapes (Vitis spp.) have slender coiling structures that attach to other plants or structures 

(tendrils).

English ivy

Amadej Trnkoczy
20

TREES and SHRUBS

Old-man’s-beard

CLVI6

Katie Barndt Amadej Trnkoczy

King County Noxious Weed Control Program

Katie Barndt
21

TREES and SHRUBS

Clematis vitalba L. CLVI6

Synonyms: Traveler’s joy, virgin’s bower.

Plant: Woody vine up to 40 feet long with compound leaves, clusters 

of small, white flowers and distinctive “hairy-looking” fruit. Family: 

Ranunculaceae (buttercup).

Stem: Stems are grooved, freely branching, and reddish to purplish when young, 

brown and woody when old.

Leaves: Leaves are opposite, compound with leaflets on either side of a central 

axis (pinnate), with 5–7 leaflets up to 3 inches long, and deciduous. Leaflets are 

heart-shaped with margins that can be smooth (entire) or have pointed (dentate) 

or rounded (crenate) teeth; the leaflet at the tip sometimes has 1–3 lobes. Petioles 

are long, and act as tendrils.

Flowers: Flowers are arranged in a branched clump (cyme) of 5–22 flowers that are 

attached in the joints where leaves attach to stems (axils) and at the ends of stems. 

Flowers are up to 1 inch wide, with no petals, 4 creamy white sepals that are 

densely hairy on both sides, and about 50 stamens and 20+ pistils.

Fruit and seeds: Dry, closed fruit are reddish when mature, with long, feather-like 

hairs.

Habitat: Forests, riparian areas, roadsides, disturbed areas, to 500 feet elevation.

Similar-looking plants: Western white clematis (C. ligusticifolia Nutt.) looks very 

similar but is found in drier habitats, has unisexual flowers on separate plants, 

coarsely toothed leaves on flowering stems (not smooth), and does not tend to 

dominate other vegetation with dense vigorous growth.

Old-man’s-beard

Katie Barndt

Amadej Trnkoczy

Dave Powell, USDA Forest Service, Bugwood.org

Below: Western white clematis (Clematis ligusticifolia Nutt.).
22

TREES and SHRUBS

Cotoneasters

COFR3 COPA14 COLA18

Below: Orange cotoneaster (COFR3).

Below and right: Silverleaf cotoneaster (COPA14).

Katie Barndt Katie Barndt

Katie BarndtKatie Barndt

Katie Barndt

M.L. Charters
23

TREES and SHRUBS

1.Orange cotoneasterCotoneaster franchetii Boiss. COFR3

2.Silverleaf cotoneasterCotoneaster pannosus Franch. COPA14

3.Milkflower cotoneasterCotoneaster lacteus W.W. Smith COLA18

Synonyms: (2) firethorn, Cotoneaster pannosa Franch.; (3) Parney’s or 

rockspray cotoneaster, red custerberry, Cotoneaster lactea W.W.Sm., 

Cotoneaster parnyei Hort.

Plant: Evergreen shrub with many arching branches to 10 feet tall, 

single (simple) leaves, small white to pink “roselike” (5-petaled) 

flowers and orange to red berries. Family: Rosaceae (rose).

Stem: Stems are thin, dark brown, and covered with hairs when young. 

Branches are generally arching, and twig tips, leaf stalks, and stipules are 

typically densely covered with short woolly hairs.

Leaves: Leaves are alternate, single (simple), and evergreen (semievergreen), 

with leaf blades that are elliptic to egg shaped (ovate or obovate), with 

short stalks (petioles), and densely covered with hairs on the lower sur-

face. Leaves of the orange cotoneaster are 3⁄4–11⁄4 inches long, dark green and 

glossy on the upper surface. Milkflower leaves are larger, 1–2 3⁄4 inches long. 

Silverleaf leaves are 3⁄4–13⁄4 inches long, with a dull green upper surface.

Flowers: Flowers are solitary or in a flat cluster at the ends of branches 

(corymb), 1⁄4–1⁄2 inch wide, with 5 petals, 5 sepals, many stamens, and 

2–5 pistils. Orange cotoneaster flowers are cup shaped and pink. Milkflower 

flowers are white, often in large clumps, whereas silverleaf flowers are also 

white, but often in small tight clumps. 

Fruit and seeds: Berrylike fruits are about 1⁄4 inch wide with persistent sepals. 

Orange cotoneaster fruits are orange red, usually with 3 seeds. Milkflower fruits 

are red, have 2 seeds, and are egg shaped (ovoid), whereas silverleaf fruits are 

also red with 2 seeds, but are nearly spherical.

Habitat: Disturbed places, mixed evergreen forest, coastal scrub, and grassland, often near residential areas.

Similar-looking plants: Firethorns (Pyracantha spp.) are common ornamental 

shrubs with small, orange to red, berrylike fruits, but their stems have thorns; 

most firethorns also have leaves with finely sharp-toothed (serrate) margins.

Below: Milkflower cotoneaster (COLA18).

Cotoneasters

Katie Barndt

Katie BarndtKatie Barndt
24

TREES and SHRUBS

Butterfly bush

BUDA2

Michael Apel

Katie Barndt

Katie Barndt

Katie Barndt
25

TREES and SHRUBS

Buddleja davidii Franch. BUDA2

Synonyms: Orange eye butterflybush, summer lilac.

Plant: Large, arching, woody shrub 10–15 feet tall 

with large lance-shaped leaves and abundant, large 

pyramidal-shaped clusters of purple flowers. Family: 

Buddlejaceae (Loganiaceae).

Stem: Young stems are distinctly angled with 4–6 (8) 

sides, greenish to gray green, and with many small 

hairs. Older stems develop brown furrowed bark.

Leaves: Leaves are opposite, single (simple), 

deciduous or semievergreen. Leaves are lance shaped 

(lanceolate), 4–10 inches long and 1–3 inches wide 

narrowing to a pointy (acuminate) tip. Leaf margins have 

sharp teeth (serrate), and upper surfaces are dark 

green to grayish green and leathery, while lower 

surfaces are grayish and covered with short hairs.

Flowers: Flowers are grouped in upright or nodding 

cylindrical or pyrimidal-shaped clumps (panicle) 

6–10 inches long. Flowers are about 1⁄4 inch long and 

bell shaped, 4 fused petals, 4 fused sepals, 4 stamens, 

and 1 style. Flower color ranges from light purple with 

yellow or orange at the mouth to deep purple. 

Fruit and seeds: Dry fruit (capsule) is 1⁄4–1⁄3 inch long 

and splits into two parts.

Habitat: Riparian areas, north coast coniferous forest, 

roadsides, clearcuts.

Butterfly bush

Institute for Applied Ecology
26

TREES and SHRUBS

Tamarisk

TARA TAPA4

Below: Saltcedar (TARA). Below and right: Smallflower tamarisk (TAPA4). Steven Perkins Steven Perkins

Barry Rice

Joseph M. DiTomaso
27

TREES and SHRUBS

1.Saltcedar, Tamarix ramosissima Ledeb.TARA

2.Smallflower tamarisk, Tamarix parviflora DC.TAPA4

Synonyms: Tamarisk, many Tamarix spp. names.

Plant: Large, deciduous shrubs to small trees, with many erect or arching basal 

branches. Leaves are tiny and scalelike, on many branching, slender stems. 

Tamarix species are not easily distinguishable and hybridize extensively. Saltcedar 

is typically < 20 (26) feet tall, whereas smallflower tamarisk is typically 12–15 feet 

tall. Family: Tamaricaceae.

Stem: Stems are slender, typically <1 inch in diameter, smooth and often arching, 

and brown to purplish in color.

Leaves: Leaves are alternate, single (simple), and deciduous, bright green, and 

grow overlapping and scalelike on many branching, slender stems. Leaves are 

lance shaped (lanceolate) with a narrow pointed tip and up to 1⁄8 inch long. Leaves 

are stalkless (sessile), and have salt-secreting glands, so salt is often visible on the 

leaves. Saltcedar leaves have more blue color than smallflower tamarisk.

Flowers: The tiny flowers are grouped in small narrow clusters up to 3 inches 

long (raceme), but the shoots bearing the flower clusters may be up to 3 feet 

long, producing a showy display. Saltcedar flowers have 5 pink to white petals, 5 

sepals, and 5 stamens. Smallflower tamarisk flowers have 4 light to dark pink petals, 

4 sepals, and 4 stamens.

Fruit and seeds: The dry fruit (capsule) is less than 0.02 inch (<0.5 mm) long, 

with many small seeds, and the petals can persist on fruits.

Habitat: Riparian areas, desert washes, seeps and springs, ditches, roadsides, 

and disturbed areas.

Similar-looking plants: Other Tamarix species that are less common in our 

region, including Athel tamarisk (T. aphylla (L.) Karst.), French tamarisk (T. gallica L.), 

and Chinese tamarisk (T. chinensis Lour.).

Tamarisk

Below: Smallflower tamarisk (TAPA4).

Joseph M. DiTomaso
28

FORBS

Knotweeds

POCU6

On this page: Japanese knotweed (POCU6).

Institute for Applied EcologyInstitute for Applied Ecology

Randall G. Prostak Louis-M. Landry Richard Old, XID Services, Inc.
29

FORBS

1. Japanese knotweed, Polygonum cuspidatum Sieb. & Zucc. POCU6

2. Himalayan knotweed, Polygonum polystachyum POPO5

 Wallich ex Meisn.

3. Giant knotweed, Polygonum sachalinense POSA4

 F. Schmidt ex Maxim.

4. Bohemian knotweed, Polygonum x bohemicum (J. Chrtek & POBO10

 Chrtková) Zika & Jacobson (P. cuspidatum x P. sachalinese)

Synonyms: (1) Japanese bamboo, Japanese arrowroot, Japanese fleeceflower, Mexican bamboo, 

Fallopia japonica (Houtt.) Ronse Decr., Reynoutria japonica Houtt., Pleuropterus cuspidatus 

(Siebold & Zucc.) Moldenke, Pleuropterus zuccarinii Small; (2) cultivated knotweed, bell-shaped 

knotweed, Persicaria wallichii Greuter & Burdet, Aconogonum polystachyum (Wall. ex Meisn.) H. 

Haraldson; (3) Sakhalin knotweed, Fallopia sachalinensis (F. Schmidt ex Maxim.) Ronse Decr., 

Reynoutria sachalinensis (F. Schmidt ex Maxim.) Nakai; (4) Bohemian knotweed, Fallopia x

bohemicum (Chrtek & Chrtková) J.P. Bailey.

Plant: Shrublike perennial forb, growing in clumps with erect to somewhat arching canelike 

stems 6–10 (18) feet tall, with large leaves and feathery-looking flower clusters. Family: 

Polygonaceae (buckwheat).

Stem: Stems are erect with few branches, grooved, hollow, jointed and swollen at the nodes, 

with papery sheaths (ocrea) at the stem base and above each node (but deciduous in 

mature Japanese knotweed). Stem color is green, turning to reddish brown when mature.

Leaves: Leaves are alternate, simple, and deciduous. Japanese knotweed leaves are egg shaped 

(ovate), 2–6 inches long and at least 2⁄3 as wide, with a pointy (acuminate) tip and a round or 

squared-off base, with short clumps of hairs on the lower surface midvein. Himalayan leaves are 

lance shaped (lanceolate), 4–8 inches long and narrow, with a squared-off or heart-shaped 

(cordate) base with two lobes, and are covered with dense hairs, especially on the lower surface. 

Giant knotweed leaf blades are egg shaped (ovate) to nearly rectangular (oblong), 6–14 inches 

long and 2⁄3 as wide, with a cordate base and narrow tip, with long wavy hairs on the lower surface 

midvein. Bohemian knotweed leaves lower on the stem have a cordate base and are more squared 

off on upper leaves, with short hairs with a triangular base on the lower surface midvein. 

Flowers: Flowers are small and found in long, branched clusters (panicles) with no petals 

and 5 sepals. Japanese knotweed clusters are up to 6 inches long and white to greenish white. 

Himalayan clusters are 8–14 inches long and white to pinkish. Giant knotweed clusters are 1–4 

inches long and greenish white to white. Bohemian knotweed flowers are in between Japanese 

and giant knotweeds.

Fruit and seeds: Dry fruits are egg shaped (ovoid), brown to black, smooth, and shiny, with 

persistent sepals.

Habitat: Riparian areas, wetlands, forest edges, roadsides, and disturbed areas.

Similar-looking plants: Aruncus dioicus (Walter) Fernald is a native herbaceous perennial 

with feathery plumes of small white flowers in the spring and summer. It has compound leaves. 

Below: Japanese knotweed (POCU6).

Knotweeds

Andrew Gray
30

FORBS

POPO5 POSA4

Knotweeds (continued)

Himalayan knotweed (POPO5).

Himalayan knotweed (POPO5).

Joseph M. DiTomaso Joseph M. DiTomaso

Giant knotweed (POSA4).

Joseph M. DiTomaso

Giant knotweed (POSA4).

Joseph M. DiTomaso
31

FORBS

Composite (Asteraceae) Differentiation

The following identification tips only apply to species groups covered in this guide. 

Aster flowers are found in “heads,” with many tiny flowerlets grouped in a cylinder 

above green or brown bracts (phyllaries). The color, shape, and spininess of the 

bracts is often key to distinguishing species. Two types of flowerlets can be found: 

disk, which are tubular and generally in the center of the flower; and ray, which 

are generally on the outer edge of the flower with sunflower-like flat petals.

• Knapweeds do not have spiny leaves and have white, purple, or pink 

flowers that do not have ray flowerlets.

• Starthistles do not have spiny leaves and have yellow flowers that do not

have ray flowerlets.

• Thistles have spiny leaves. Flowers do not have ray flowerlets.

• Skeletonweed has smooth leaves and yellow flowers that do have ray 

flowerlets, but no disk flowerlets.

• Hawkweeds have hairy leaves and yellow or orange flowers that do have 

ray flowerlets, but no disk flowerlets. (A native species has white flowers.)

• Daisies have the classic sunflower flowerhead with the small disk flowers 

in the center and the large-petaled ray flowers around the edge.

Spotted knapweed (CESTM).

Maltese starthistle (CEME2).

Italian thistle (CAPY2). Rush skeletonweed (CHJU).

Orange hawkweed (HIAU). Oxeye daisy (LEVU).

Patrick J. Alexander

Jordan Zylstra

Joseph M. DiTomaso

Institute for Applied Ecology

Carol W. Witham

Joseph M. DiTomaso
32

FORBS

Knapweeds

Below: Russian knapweed (ACRE3).

ACRE3 CESTM CENI3 CEDI3 CEVIS 2

Below: Spotted knapweed (CESTM).

Fred Hrusa

© John M. Randall/TNC© John M. Randall/TNC

© Barry A. Rice/TNC

Patrick J. Alexander
33

FORBS

1. Russian knapweed, Acroptilon repens (L.) DC. ACRE3

2.Spotted knapweed, Centaurea stoebe L. ssp. CESTM (CEBI2*)

 micranthos (Gugler) Hayek

3.Meadow knapweed, Centaurea nigrescens Willd.CENI3 (CEDET*)

4.

Diffuse knapweed, Centaurea diffusa Lam.CEDI3

5.

Squarrose knapweed, Centaurea virgata Lam.CEVIS2 (CETR8*)

 var. squarrosa (Willd.) Gugler

Synonyms: (1) Hardheads, Russian starthistle, Turkestan thistle, 

C. picris Pall ex Willd., C. repens L.; (2) C. maculosa auct. non Lam., 

C. biebersteinii DC.*; (3) C. debeauxii Gren. & Gord. ssp. thuillieri Dostal*, 

C. pratensis Thuill; (4) white knapweed, Acosta diffusa (Lam.) Soják; 

(5) C. triumfettii auct. non All.*, C. squarrosa Willd.

*Older nomenclature used in NRCS PLANTS version from 2000.

Plant: Herbaceous annuals or perennials with clusters of white, pink, or 

purple flower heads, starting out as basal rosettes until erect branched 

flowering stems develop in late spring or summer, growing up to 4 feet tall. 

Family: Asteraceae (aster, composite).

Stems and leaves: Leaves of rosettes and lower stems are deeply lobed 

(pinnate). Stem leaves are alternate and do not extend down the stem as 

wings.

Russian: Lower leaves deeply lobed and 2–4 inches long, upper leaves 

entire or toothed. Stems are leafy and mostly covered with cobwebby 

gray hairs.

Spotted: Multistemmed from the crown, lower leaves are lobed and 

4–8 inches long, upper leaves are mostly lobed.

Meadow: Multistemmed from the crown.

Diffuse: Lower leaves are lobed and 4–8 inches long, upper leaves are 

smooth margined (entire).

Squarrose: Lower lobed leaves are 4–8 inches long, upper leaves are 

smooth margined (entire), narrow and uniform (linear) or very reduced 

(bractlike), mostly lacking at flowering.

(continued on page 35)

Knapweeds

Below: Spotted knapweed (CESTM).

Institute for Applied Ecology
34

FORBS

Knapweeds (continued)

Below: Meadow knapweed (CENI3). Below: Diffuse knapweed (CEDI3). Below: Squarrose knapweed (CEVIS2). Bogdan

Fred Hrusa

Institute for Applied Ecology Steve Dewey

Steve Dewey, Utah State University, Bugwood.org
35

FORBS

Flowers: Knapweeds (continued) The knapweeds have composite heads of small disk flowerlets and are 

primarily distinguished by the color and shape of the bracts (phyllaries) on the 

flower heads. Old flower stems can persist after senescence, aiding in identification.

Russian: Bracts are oval shaped, green at the base, and with papery 

margins.

Spotted: Bracts are green at the base and black at the tips with comblike 

points on the margins.

Meadow: Bracts are shiny gold to brown and fringed, without spines at the tip.

Diffuse: Bracts are pale green and straw colored with comblike points on the 

margins and a spine at the tip up to 0.1 inch (3 mm) long.

Squarrose: Bracts are pale green to straw colored with a spine at the tip 

usually curved away from the head and downward.

Fruit and seeds: Seeds are nearly rectangular (oblong), 0.1–0.15 inch (3–4 mm), 

tapered to a rounded base with a notch on one side.

Habitat: Open forests, roadsides, rangeland, grassland, and disturbed areas.

Similar-looking plants: There are several much less common knapweeds in 

California. Knapweeds are distinguished from thistles by not having spiny leaves, 

and from starthistles by not having spiny yellow flowers.

Cindy Roche, Bugwood.org

Below: Squarrose knapweed (CEVIS2).
36

FORBS

Starthistles

CEME2 CESO3

Above and right: Maltese starthistle (CEME2).

Below: Yellow starthistle (CESO3).

Above: Yellow starthistle (CESO3).

Jordan ZylstraJordan Zylstra

Thomas Stoughton

Institute for Applied Ecology

Institute for Applied Ecology
37

FORBS

1.Maltese starthistle, Centaurea melitensis L.CEME2

2.Yellow starthistle, Centaurea solstitialis L.CESO3

Synonyms: (1) Tocalote, Malta starthistle, Napa thistle; (2) golden starthistle, 

yellow cockspur, St. Barnaby’s thistle, Leucantha solstitialis L.

Plant: Simple to bushy herbaceous winter annuals, with spiny yellow-flowered 

heads and wiry stems, growing up to 3 feet tall. Family: Asteraceae (aster, composite).

Stems and leaves: Stems are rigid, single in small plants to openly branched from 

near the base in large plants. Bases of leaves extend down the stems in long ridges 

(“wings”). Leaves are alternate, leaf margins are smooth, toothed, or wavy, and 

stems and leaves are covered in wooly hairs. Basal rosette leaves typically wither 

by flowering time.

Maltese: Leaves are often grayish green, mostly straight and narrow to nearly 

rectangular (oblong).

Yellow: Leaves are grayish green to bluish green, and lower stem leaves are 

sometimes deeply lobed.

Flowers: The starthistles have composite heads of small disk flowerlets. Heads are 

round to oval, spiny, and single on the ends of stems, although vigorous plants may 

develop flower heads in the joints where branches connect to stems. The bracts on 

the flower heads (phyllaries) have a long central spine and 2 or more pairs of short 

lateral spines. Old flower stems can persist after senescence, aiding in identification.

Maltese: Flowers from April to July. The central spine of the main bracts is 1⁄4–1⁄2 

inch long, slender, and often purple to brown tinged. Lateral spines are usually in 

3–4 pairs, the upper pair near the middle of the central spine. Central spine stays 

on after senescence.

Yellow: Flowers from June to December. The central spine of the main bracts is 

1⁄2–1 inch long, stout, and yellowish to straw colored throughout. Lateral spines are 

typically in 2–3 pairs at the base of the central spine. Central spine falls off after 

senescence.

Fruit and seeds: Seeds are barrel-shaped, 0.1–0.15 inches, slightly flattened with 

a notch on one side of the base.

Habitat: Open disturbed sites, open woodland, grassland, rangeland, pastures, 

and roadsides.

Similar-looking plants: There are several less common starthistles in California, 

including purple (Centaurea calcitrapa L.) and Iberian (C. iberica Trevir. ex Spreng.), 

which have purple flower heads.

Starthistles

Below: Yellow starthistle (CESO3).

Institute for Applied Ecology
38

FORBS

Thistles

CIAR4 CIVU ONAC CANU4 CAPY2

Below and right: Canada thistle (CIAR4).

Katie Barndt

Katie Barndt

Steve Dewey, Utah State University, Bugwood.org
39

FORBS

1.Canada thistle, Cirsium arvense (L.) Scop. CIAR4

2.Bull thistle, Cirsium vulgare (Savi) Ten. CIVU

3.Scotch thistle, Onopordum acanthium L.ONAC

4.

Musk thistle, Carduus nutans L. CANU4

5.

Italian thistle, Carduus pycnocephalus L. CAPY2

Synonyms: (1) Corn thistle, creeping thistle, Breea arvensis (L.) Less., Carduus 

arvensis (L.) Robson, Cirsium incanum (S.G. Gmel.) Fisch. ex M. Bieb.; (2) 

bank thistle, bird thistle, common thistle, spear thistle, Ascalea lanceolata (L.) 

Hill, Carduus lanceolatus L., Carduus vulgaris Savi; (3) cotton thistle, downy 

thistle, jackass thistle, winged thistle; (4) giant plumeless thistle, nodding thistle, 

plumeless thistle, Carduus leiophyllus Petrovič; (5) compact-headed thistle, shore 

thistle, slender thistle.

Plant: Erect herbs with prickly foliage and flower heads of purple, pink, or white 

disc flowerlets, 1–7 feet tall. For most species, leaf bases extend nearly all the 

way down stems between leaves (decurrent) as spiny “wings.” Family: Asteraceae 

(aster, composite).

Stems and leaves: 

Canada: Creeping roots (rhizomes) often result in dense clumps of stems. 

Stems are slender, mostly hairless and leafy, with small inconspicuous 

“wings.” Leaves are nearly rectangular (oblong) to lance shaped (lanceolate), 

2–8 inches long, with mostly hairless upper surfaces and margins that are 

mostly smooth to shallow lobed and toothed, with main leaf prickles about 

0.1–1⁄4 inch long. 

Bull: Stems are usually solitary and branched, loosely covered with white cobwebby hairs, sometimes glandular, and with conspicuous spiny “wings.” Basal 

rosette leaves are 4–15 inches long, moderate to deeply lobed and toothed, 

with main prickles mostly 1⁄4-1⁄2 inch long. Stem leaves are smaller, more deeply 

lobed, and spinier than rosette leaves. Leaves have prickly hairs above and 

cottony surfaces below. 

Scotch: Stems are branched, 5–10 feet tall, with conspicuous spiny “wings” 

along the entire length of the stems. Basal rosette and stem leaves are alternate, 4–20 inches long, and very spiny, with toothed or shallow-lobed margins. 

Leaves are covered with wooly, pale grey hairs.

Musk: Stems are branched near the top, with narrow spiny “wings” along the 

entire stem. Leaves are lobed, hairless to sparsely hairy, with lower leaves 

4–15 inches long.

Italian: Stems branched near the top, with spiny “wings” up to 1⁄4 inch wide 

along most of the stem, often interrupted near the flower heads. Leaves lobed 

and mostly covered with woolly hairs, 4–6 inches long. (continued on page 41)

Thistles

Below: Bull thistle (CIVU).

Institute for Applied Ecology

Steve Dewey, Utah State University, Bugwood.org

Steve Dewey, Utah State University, Bugwood.org
40

FORBS

Thistles (continued)

Below: Scotch thistle (ONAC). Below: Musk thistle (CANU4). Below: Italian thistle (CAPY2). Gary A. Monroe Gary A. Monroe Louis-M. Landry © Steven J. Baskauf/TNC Thomas Stoughton Louis-M. Landry

Carol W. Witham Alfred Brousseau
41

FORBS

Flowers: Thistles (continued)

Canada: Blooms June to October with clusters of small flower heads, with the 

green bract part of the head (involucre) 1⁄4–1 inch in diameter and 1⁄2–1 inch long, 

the bracts without spines (flimsy spines about 0.04 inch (1 mm) long can be 

found on close inspection). Flowerlets are pink, purple, or white, and plants are 

unisexual, with male flowers generally <1⁄2 inch long and female flowers generally 

>1⁄2 inch long.

Bull: Blooms June to October with large flower heads, with the green bract part of 

the head (involucre) 3⁄4-11⁄2 inches in diameter and 1–11⁄2 inches long, the bracts 

with spines up to 1⁄4 inch long. Each head has at least 1 bractlike leaf just below. 

Flowerlets are purple (rarely white), mostly 1–11⁄2 inches long.

Scotch: Blooms July to September with large, mostly solitary flower heads, but 

found in clusters of 2–7 too, the bracts with spines up to 1⁄4 inch long and 

covered with short hairs and a few cobwebby hairs. Flowerlets are white or 

purple, about 1 inch long.

Musk: Blooms June to September, with large heads 3⁄4–21⁄2 inches diameter, single 

on each stem and usually nodding at the end of about 1 inch long stalks. Bracts 

are wide and spine tipped; flowerlets are purple, 3⁄4–1 inch long.

Italian: Blooms May to July, with heads 1⁄2–3⁄4 inch diameter, stalkless or nearly so 

and usually with 2–5 in a clump. Bracts are narrow and spine tipped, with 

persistent patches of wooly hairs at the bases; flowerlets are pink to purple, 

about 1⁄2 inch long.

Fruit and seeds: Seeds are oval to elliptic, <1⁄4 inch long, attached to feathery tan to 

white (pink to reddish for scotch) bristles that catch the wind.

Habitat: Open disturbed sites, recently logged forest, open woodland, rangeland, 

pastures, and roadsides; not tolerant of shade. Scotch thistle is often found in sites 

with high soil moisture.

Similar-looking plants: There are many native thistles that generally do not dominate 

sites (e.g., not weedy). Unlike other weedy composites, thistles have spiny leaves.

Below: Italian thistle (CAPY2).

Institute for Applied Ecology
42

FORBS

Rush skeletonweed

CHJU

Fred Hrusa

Joseph M. DiTomasoJoseph M. DiTomaso Fred Hrusa

Joseph M. DiTomaso
43

FORBS

Chondrilla juncea L. CHJU

Synonyms: Devil’s-grass, hogbite, naked weed, skeleton weed.

Plant: Herbaceous perennial with rigid, wiry flower stems to 3 feet tall and milky 

sap. Plants grow as basal rosettes until flowering stems develop. Family: Asteraceae 

(aster, composite).

Stems and leaves: Rosette leaves are lance shaped (oblanceolate) and shallowly 

lobed, with lobes opposite each other and pointing backward, looking a lot like dandelion or chicory, and withering as flowering stems develop. Stems are nearly leafless and highly branched, with the lowest 4–6 inches covered in coarse, bristly, 

downward-pointing hairs. When present, stem leaves are bractlike and resemble 

small rosette leaves. Rigid stems with downward-pointing hairs persist long 

after flowering, with reddish leaves and clusters of old flower heads.

Flowers: Blooms May until first frost, with small (3⁄4 inch wide) 5–15 petaled bright 

yellow flowers in leaf joints on stems (axils) or at tips. Petals are strap-like, about 

1⁄2 inch long, with 5 lobes at the tip.

Fruit and seeds: Seeds about 0.15 inch (3 to 4 mm) long, and tapered at both ends, 

and attached to feathery pappus of fine white bristles.

Habitat: Disturbed roadsides, open forest, rangeland, and pasture. Grows best on 

dry sandy or gravelly soils.

Similar-looking plants: Rosette leaves are similar to dandelion (Taraxacum 

officinale F.H. Wigg) in having hairless leaves with paired lobes pointed backward 

and milky sap. Dandelion differs by having unbranched flower stems that are slightly 

succulent, leafless, and hollow, and generally occurring in lawns and gardens. In 

contrast to both, basal rosette leaves of chicory (Cichorium intybus L.) have lobes 

that point outward or forward, are not always opposite, and basal leaves usually 

have a few rough, coarse hairs. Skeletonweed leaves are also often reddish, unlike 

dandelion or chicory.

Rush skeletonweed

Gary L. Piper, Washington State University, Bugwood.org
44

FORBS

Hawkweeds

On this page: Orange hawkweed (HIAU).

HIAU

HICA10

Montana Statewide Noxious Weed Awareness and Education Archive

Michael Shephard, USDA Forest Service, Bugwood. org

Joseph M. DiTomaso

Joseph M. DiTomaso
45

FORBS

1. Orange hawkweed, Hieracium aurantiacum L. HIAU

2. Yellow hawkweed, Hieracium caespitosum Dumort. HICA10

Synonyms: (1) Devil’s paintbrush, orange paintbrush, red daisy, Pilosella 

aurantiaca (L.) F.W. Schullz & Sch. Bip.; (2) meadow hawkweed, Hieracium 

pratense Tausch.

Plant: Herbaceous perennial with basal rosette and flowering stems to 2 

feet tall, covered in long hairs, with orange-red dandelion-like flowers 

and milky sap in all plant parts. Family: Asteraceae (aster, composite).

Stems and leaves: Basal rosette leaves are nearly rectangular-elliptical 

(oblong-elliptic) to lance shaped (lanceolate), 1–8 inches long and usually 

>1⁄2 inch wide, with smooth or slightly toothed margins. Upper and lower leaf 

surfaces are densely covered with long, soft, spreading hairs. Flowering 

stalks are usually leafless and covered with black, glandular hairs. Aboveground runners (stolons) spread from established plants and root at the 

tips, creating dense mats of plants. Stems do not persist after senescence.

Flowers: Blooms June–September with a cluster of a few to several flower 

heads at the end of stalks. 

Orange: Heads consist of orange-red flowers with straplike petals 

with 5 lobes at the tip (ligulate) that turn purplish when dry. Flower-head 

bracts (phyllaries) are covered with glandular and black hairs.

Yellow: Heads consist of yellow flowers with straplike petals with 5 

lobes at the tip (ligulate).

Fruit and seeds: Seeds are about 0.05 inch (1.5–2 mm) long, cylindrical, ribbed lengthwise, dark, and attached to feathery pappus of fine white 

bristles.

Habitat: Disturbed roadsides, open forest, rangeland, and pasture. 

Similar-looking plants: There are several invasive nonnative hawkweeds 

in addition to several common natives; all of the nonnative species can 

spread with aboveground runners (are stoloniferous), whereas the natives 

do not. Common natives encountered in forested environments include 

the white, slender, and Scouler’s hawkweeds (Hieracium albiflorum Hook., 

H. gracile Hook., and H. scouleri Hook., respectively). In addition to the 

lack of stolons, white hawkweed has white flowers (slender and Scouler’s 

are yellow), slender hawkweed leaves are mostly hairless, and Scouler’s 

hawkweed has leafy stems (Wilson 2006).

Hawkweeds

Below: Yellow hawkweed (HICA10).

Above: Orange hawkweed (HIAU).

Michael Shephard, USDA Forest Service, 

Bugwood.org

Richard Old, XID Services, Inc., Bugwood.org

Tom Heutte, USDA Forest Service, Bugwood.org Joseph M. DiTomaso
46

FORBS

Oxeye daisy 

Institute for Applied EcologyInstitute for Applied Ecology Institute for Applied Ecology

Patrick J. Alexander
47

FORBS

Leucanthemum vulgare Lam. LEVU

Synonyms: Butter daisy, field daisy, golden flower, moon daisy, white daisy, 

Chrysanthemum leucanthemum L., Leucanthemum leucanthemum (L.) Rydb.

Plant: Herbaceous perennial with basal rosette leaves and flowering stem 

1–3 feet tall, with white daisy flowerheads (small disk flowers in the center 

and large-petaled ray flowers around the edge) and creeping roots that result in 

dense clumps of plants. Family: Asteraceae (aster, composite).

Stems and leaves: Rosette leaves are hairless, lance shaped (oblanceolate) and 

irregularly lobed, with lobes about half the width from edge to midvein, and 

coarsely toothed leaf margins, with teeth usually rounded. Rosette and leaves on 

lower stems are up to 6 inches long and taper to a stalk that is about half the leaf 

length. Upper stem leaves are stalkless, nearly rectangular (oblong), and usually 

<2 inches long at mid-stem.

Flowers: Blooms May to August with yellow centers 1–2 inches wide surrounded by 20–30 white petals 1⁄2–1 inch long (1–3 inches total width). Flowerheads 

occur singly on the end of a long stalk.

Fruit and seeds: Seeds are lance 

shaped (lanceolate), curved, about 0.1 

inch (1.5 to 2.5 mm) long, dark brown, 

and ribbed lengthwise, with no feathery 

pappus of fine white bristles.

Habitat: Disturbed roadsides, pastures, 

grassland, coastal scrub, and open 

forests. Often does well on moist clay 

soils.

Similar-looking plants: Max 

chrysanthemum (Leucanthemum 

maximum (Raymond) DC.) is an 

uncommon nonnative perennial with 

larger white daisylike flower heads 

3–4 inches in diameter and regularly 

toothed leaves.

Oxeye daisy 

LEVU

Steven J. Baskauf
48

FORBS

Purple loosestrife

LYSA2

Katie BarndtKatie Barndt

Katie Barndt

Katie Barndt

Ohio State University Weed Lab Archives, Bugwood. org
49

FORBS

Lythrum salicaria L. LYSA2

Synonyms: Bouquet-violet, purple lythrum.

Plant: Herbaceous bushy perennial with stiff four-sided stems and showy, pinkish 

purple flower spikes growing 6–10 feet tall. Family: Lythraceae.

Stems and leaves: Stems are simple or branched, square or 5-angled in cross 

section, covered in short hairs. Leaves are mostly opposite or whorled (upper 

sometimes alternate), lance shaped, 2–6 inches. Leaf bases are round or slightly 

heart shaped, with no stalk connecting to stems (sessile). Leaf margins are smooth. 

Senescing foliage often turns red. The dead, brown, opposite-branched stems often 

persist through winter and may retain a few seed capsules.

Flowers: Flowers from June to September. Small magenta flowers with 5–7 

petals are produced on tall clusters of flower spikes (consisting of stalkless flowers 

on an unbranched long axis). Petals are 1⁄3–1⁄2 inch (8–14 mm) long with slightly wavy 

margins. Stamens number around 12.

Fruit and seeds: Dry fruit (capsules) are nearly rectangular (oblong) to egg shaped 

(ovoid), about 0.2 inch long, with numerous flattened seeds 0.02–0.04 inch 

(0.5–1 mm) long. 

Habitat: Moist or marshy areas and disturbed sites. Tolerates some shade.

Similar-looking plants: California loosestrife (Lythrum californicum Torr. & A. Gray) 

is a native that grows to 2 feet tall, and has hairless stems, and petals mostly <1⁄3 inch 

(4 to 8 mm) long. Rose spirea (Spiraea douglasii Hook.) is a native shrub with round 

stems and toothed leaf tips, with tiny, light pink flowers in dense clumps at the top of 

the plant. Fireweed (Chamerion angustifolium (L.) Holub) has round stems, longer 

leaves with a distinct midvein, and 4-petaled flowers on stalks that split open when 

dry to release fluffy white seeds.

Purple loosestrife

Barry Rice, sarrecenia.com, Bugwood.org

Below: Fireweed (Chamerion 

Below: Rose spirea (Spiraea douglasii Hook.). angustifolium (L.) Holub). Lindsay Koepke, Natural Resources Conservation Service

Joy Viola, Northeastern University, Bugwood.org
50

FORBS

Dalmatian toadflax

LIDA

Institute for Applied Ecology Institute for Applied Ecology

K. George Beck & James Sebastian, Colorado State University, Bugwood. org

K. George Beck & James Sebastian, Colorado State University, Bugwood. org
51

FORBS

Linaria dalmatica (L.) P. Mill LIDA

Synonyms: Broad-leaved toadflax, wild snapdragon, Linaria genistifolia (L.) Mill. 

ssp. dalmatica (L.) Maire & Petitm.

Plant: Erect herbaceous perennial up to 4 feet tall, with showy yellow snapdragonlike flowers (tubular base with a flared upper lip and a bent-downward lower lip). 

Family: Scrophulariaceae (figwort).

Stems and leaves: Solitary stems, often branched near the top, arise from creeping 

rootstock. Stem and leaves have a waxy coating. Leaves are heart shaped, clasp 

the stem at their bases, and are stiff and point upwards. Leaves are usually bluish 

green and covered with a whitish bloom.

Flowers: Blooms May to September with showy, snapdragon-like bright yellow 

flowers that are two-lipped and 5-lobed, with a long downward-pointing spur. 

Throat and lower lip are hairy, with white or orange hairs. Flowers are 1–2 inches 

long including the spur. Flowers in bud are often purplish at the tip.

Fruit and seeds: Dry fruit (capsules) are round, 0.1–0.33 inch long and 

2-chambered, opening by irregular slits at the end to release numerous black 

to dark brown pyramid-like tiny (0.05 inch; 1.2 mm long) seeds. 

Habitat: Disturbed open sites, fields, pastures, rangeland, forest clearings, and 

roadsides; grows best in cool, semiarid climates and coarse soils.

Similar-looking plants: Yellow toadflax (Linaria vulgaris Mill.) has softer, narrow 

and uniform (linear) leaves and flowers <11⁄2 inches long, and is rarely found in 

forest habitats. Other ornamental toadflaxes have escaped cultivation, but have 

red or purple flowers.

Dalmatian toadflax

Utah State University Archive, Utah State University, Bugwood.org

Below: Yellow toadflax.

Michael Shephard, USDA Forest Service,, Bugwood. org
52

FORBS

Leafy spurge

EUES

© John M. Randall/The Nature Conservancy Steve Schoenig

Fred Hrusa Joseph M. DiTomaso
53

FORBS

Euphorbia esula L. EUES

Synonyms: Faitours-grass, wolf’s milk, Euphorbia virgata Waldst. 

& Kit. non Desf., E. discolor Ledeb., E. gmelinii Steud. 

Plant: Erect perennials up to 3 feet tall, with milky white sap, mostly 

alternate leaves, and distinctive yellow green bracts at the base of 

the flower. Plants form large clumps from deep, creeping roots. Family: 

Euphorbiaceae (spurge).

Stems and leaves: Stems are often somewhat woody at the base. 

Leaves lack stalks (petioles), are narrow and uniform (linear) to narrowly 

lance shaped (oblanceolate), and are 1–3 inches long and usually 1⁄2 inch 

wide. Leaf margins are smooth and usually hairless. Yellow-green bracts 

under the flowers are opposite, heart-shaped, and shorter and broader 

than the leaves. Shoots die back with the onset of the cold season, and 

leaves often turn reddish just before dropping.

Flowers: Blooms June to September. What appears to be one flower is a 

clump of small male and female flowers (cyathium, unique to the spurge 

family) above the large bracts.

Fruit and seeds: Dry fruit (capsules) are round, 0.1–0.2 inches long, and 

3-chambered, with 1 seed per chamber. Seeds are oval to oblong, with a 

yellowish small appendage (caruncle) near the end of attachment. 

Habitat: Disturbed open sites, fields, pastures, rangeland, and riparian 

areas.

Similar-looking plants: Yellow toadflax (Linaria vulgaris Mill.) looks 

similar in the vegetative stage prior to blooming, but the juice in the 

stems of all toadflaxes is clear whereas leafy spurge stems contain a 

milky latex when broken.

Leafy spurge

Institute for Applied Ecology

Below: Yellow toadflax.

Steve Dewey, Utah State University, 

Bugwood.org
54

FORBS

Houndstongue

CYOF

David Fenwick

Institute for Applied EcologyInstitute for Applied Ecology

Institute for Applied Ecology

Institute for Applied Ecology
55

FORBS

Cynoglossum officinale L. CYOF

Synonyms: Beggar’s-lice, dog’s tongue, gypsyflower, woolmat. 

Plant: Herbaceous biennial, forming rosettes the first year and flowering stalks 

the second year up to 4 feet tall, with clusters of reddish purple flowers. Family: 

Boraginaceae (borage).

Stems and leaves: Leaves are alternate, moderately to densely covered with 

long, soft, white hairs, lance shaped (oblanceolate) to narrowly elliptic, 2–8 inches 

long and 1–2 inches wide (shape resembles a hound’s tongue). Lower leaf bases 

taper to a stalk 1–5 inches long. Upper leaves are smaller than lower leaves and lack 

stalks (sessile). Old dead stems with fruits can persist through winter or longer.

Flowers: Blooms May to August, with dark reddish, 5-petaled, small flowers 

0.15–0.33 inch long and about 1⁄4 inch wide, in clumps at the end of drooping stems. 

Petals are just slightly longer than the sepals. Leaves usually slightly overlap the 

base of the flower clumps. Flower stalks (pedicels) are short, <1⁄2 inch long.

Fruit and seeds: Fruits consist of 4 oval, about 1⁄3-inch-long nutlets covered with 

short prickles tipped with downward-pointing barbs, on a pyramid-shaped fleshy 

base (receptacle) with a persistent tube from the pistil (style) attached to the center of 

the receptacle. 

Habitat: Disturbed open sites, often moist areas, roadsides, pastures, rangeland, 

and open woodland and forests.

Similar-looking plants: Pacific houndstongue (Cynoglossum grande Douglas ex 

Lehm.) and western houndstongue (C. occidentale A. Gray) are distinguished by 

having leaves that do not overlap the base of the flower groups, bluish flowers with 

petals conspicuously longer than sepals, and nutlets with a rounded upper surface. 

These native perennials are also not weedy.

Houndstongue

Institute for Applied Ecology

Mary Ellen (Mel) Harte, Bugwood. org

Below: Pacific houndstongue.
56

FORBS

Perennial pepperweed

LELA2

Steve Schoenig

Jennifer Forman

Frred Hrusa

Bonnie Million, National Park Service, Bugwood.org
57

FORBS

Lepidium latifolium L. LELA2

Synonyms: Broadleaf pepperweed, perennial peppercress, tall whitetop, giant 

whiteweed, Cardaria latifolia (L.) Spach.

Plant: Herbaceous perennial 1-6 feet tall, with hairless foliage, rounded to pyramidal 

clumps of small white flowers. Dense stands can form from an extensive creeping 

root system. Family: Brassicaceae (mustard).

Stems and leaves: Lower stem can be almost woody, and stems are branched. 

Leaves are alternate, lance shaped (lanceolate) to elliptic, and green to grey green in 

color. Basal leaves are larger than stem leaves, to 12 inches long and 3 inches wide, 

on a stalk 1–6 inches long, and with sharp-toothed (serrate) margins. Stem leaves are 

smaller than basal leaves, stalkless or nearly so, with a tapered base and smooth or 

slightly serrate margins. Pale brown dead stems may persist for several years.

Flowers: Blooms May to September, with a distinctive odor. Dense clumps of very 

small white flowers form at the ends of stems in a pyramidal or rounded-top shape. 

Flowers have 4 spoon-shaped petals about 0.05 inch long, 4 oval sepals sometimes covered with long simple hairs, and 6 stamens (4 long and 2 short).

Fruit and seeds: Dry fruit pods (silicles) are 2-chambered, round to oval, slightly 

flattened, without a notch at the end, about 0.1 inch long, usually sparsely to 

moderately covered with long, simple hairs, and on stalks that are much longer than 

pods. Each chamber has 1 flattened, elliptical, slightly hairy reddish brown seed. 

Seeds fall from pods throughout the winter. 

Habitat: Grows in roadsides, wet meadows, riparian areas, sand dunes, and irrigated 

pastures.

Similar-looking plants: Hoary cress (Cardaria draba (L.) Desv.), lens-podded 

whitetop (C. chalepensis (L.) Hand.-Maz.), hairy whitetop (C. pubescens (C.A. Mey.) 

Jarmol.), field pepperweed (Lepidium campestre (L.) W.T. Aiton), and clasping pepperweed (Lepidium perfoliatum L.) all grow only to about 20 inches tall, have stem leaves 

with bases that are lobed and clasp the stem, and foliage that is at least sparsely 

hairy. In addition, Cardaria usually have inflated pods greater than 0.075 inch (2 mm) 

long. Field and clasping pepperweeds do not grow in dense colonies.

Perennial pepperweed

Bonnie Million, National Park Service, Bugwood.org
58

FORBS

Hoary cress and hairy whitetop

CADR CAPU6

On this page: Hoary cress (CADR).

Joseph M. DiTomaso

Joseph M. DiTomaso

Joseph M. DiTomaso
59

FORBS

1. Hoary cress, Cardaria draba (L.) Desv. CADR

2. Hairy whitetop, Cardaria pubescens (C.Meyer) Jarmol. CAPU6

Synonyms: (1) Heart-podded hoary cress, peppergrass, pepperweed whitetop, perennial peppergrass, short whitetop, whitetop, Lepidium draba L.; (2) ball cress, hoary cress, Hymenophysa 

pubescens C.A. Mey.

Plant: Herbaceous perennials to 16 (20) inches tall, with flat-topped to rounded clumps of small 

white flowers, and small disk- to heart-shaped pods. Clonal colonies usually develop from the 

creeping roots. Family: Brassicaceae (mustard).

Stems and leaves: Stems are sparsely to densely covered with short, simple hairs. Leaves are 

alternate, grey green, and highly variable in shape, either egg shaped (obovate), lance shaped (lanceolate), nearly rectangular (oblong), or elliptic. Leaf margins can be irregularly toothed or smooth. 

Leaves are sparsely to densely covered with short, simple white hairs, particularly on the undersides. 

Basal leaves have short stalks (petioles), and upper leaves are stalkless (sessile), with lobed bases 

clasping the stem. 

Hoary cress: Leaves are up to 31⁄2 inches long and 21⁄4 inches wide, sometimes smaller, sparse to 

densely hairy, and leaf base lobes are often rounded pointy (acute). 

Hairy whitetop: Leaves are up to 3 inches long and 3⁄4 inch wide, usually much smaller, densely 

hairy, and leaf base lobes are often pointy (acute).

Flowers: Flowers are fragrant. Dense clumps of very small, 4-petaled, white flowers form at the 

ends of stems in a rounded to nearly flat-topped shape. Flowers have 6 stamens (4 long and 2 short).

Hoary cress blooms March to July and flowers have petals about 0.15 inch 

(3–4 mm) long and hairless sepals.

Hairy whitetop blooms April to October and flowers have petals about 0.1 inch (2–3.5 mm) long 

and sepals covered with short simple hairs.

Fruit and seeds: Dry fruit pods (silicles) are 2-chambered, variable, inflated, with a persistent style 

about 0.05 inch (1–2 mm) long at the end. Each chamber usually has 1–2 seeds that are oval, 

slightly flattened, reddish-brown, <0.1 inch (1.5–2 mm) long and about 0.05 inch (1–1.5 mm) wide.

Hoary cress pods are upside-down heart shaped to broadly egg shaped (ovoid), constricted 

in the middle and often 2-lobed, 0.1–0.15 inch (2.5–3.5 mm) long, 0.1–0.2 inch (3-5 mm) wide, 

and hairless.

Hairy whitetop pods are strongly inflated, spherical to egg shaped (ovoid or obovate), not constricted in the middle nor 2-lobed, are 0.15–0.2 inch (3–4.5 mm) long, 0.1–0.2 inch (2.5–4.5 

mm) wide, and covered with short hairs.

Habitat: Grows in disturbed open sites, roadsides, ditches, pastures, and orchards.

Similar-looking plants: Unlike Cardaria species, perennial pepperweed (Lepidium latifolium L.) has 

hairless leaves, stalkless stem leaves that are tapered at the base, and smaller pods (about 0.1 inch 

or 2 mm long) that are flattened, not inflated, and that have a stigma less than 1 mm long at the end. 

Perennial pepperweed is also usually >20 inches tall.

Hoary cress and hairy whitetop

On this page: Hairy whitetop (CAPU6).

Joseph M. DiTomaso

Joseph M. DiTomaso

Joseph M. DiTomaso Joseph M. DiTomaso
60

FORBS

Dyer’s woad 

ISTI

Luigi Rignanese

Alfred Brousseau

Luigi Rignanese Luigi Rignanese

Antonie Van Den Bos, http//:www.botanypictures.com
61

FORBS

Isatis tinctoria L. ISTI Dyer’s woad 

Synonyms: Marlahan mustard.

Plant: Herbaceous biennial to 4 feet tall, with bright yellow flowers and distinctive 

dark, hanging fruit. Grows as basal rosette until flower stems develop. Family: 

Brassicaceae (mustard).

Stems and leaves: Leaves are usually bluish with a distinct pale midvein, and 

covered with a white powdery bloom (glaucous). Rosette leaves are lance shaped 

(oblanceolate) to elliptic, 1–7 inches long, 1⁄2–11⁄2 inches wide, with a base that gradually tapers to a stalk 1⁄2 to 3⁄4 the length of the leaf. Leaf margins are slightly toothed to 

wavy. Upper stem leaves are alternate, stalkless, with lobed bases clasping the stem. 

Flowers: Blooms April to June with bright yellow 4-petaled flowers in clumps that 

are flat topped or umbrella shaped. Petals are spoon shaped about 0.15 inch (3–4 

mm) long, yellow sepals are shorter than petals and separate to the base, and there 

are 6 stamens (4 long and 2 short).

Fruit and seeds: Fruits are hanging, black to purplish black, flattened, nearly 

rectangular (oblong) to lance shaped (oblanceolate), 0.3–0.7 inch (8–18 mm) 

long, ridged lengthwise at the center of each side, and gradually tapered to a slender 

stalk. Each fruit has 1 seed that is oblong, grooved into 2 unequal halves, yellowish 

brown, and about 0.15 inch (3–4 mm) long.

Habitat: Grows in forest, disturbed open sites, roadsides, pastures, and rangeland, 

often in dry rocky or sandy soils.

Similar-looking plants: Dyer’s woad is distinguished from all other plants in the 

mustard family by its unique fruits.

Antonie Van Den Bos, http//:www.botanypictures.com
62

FORBS

Garlic mustard

ALPE4

Tom Heutte, USDA Forest Service, Bugwood.org

Steven J. Baskauf

Amadej Trnkoczy

Amadej Trnkoczy
63

FORBS

Alliaria petiolata (Bieb.) Cavara & Grande ALPE4 Garlic mustard

Synonyms: Alliaria, flixweed, Alliaria alliaria (L.) Britton, A. officinalis Andrz. 

ex M. Bieb., Erysimum alliaria L., Sisymbrium alliaria (L.) Scop.

Plant: Herbaceous biennial with first-year basal rosette remaining green over 

winter, producing 1–2 stems 2–4 feet tall, with white flowers. Crushed leaves and 

stems smell like garlic in early spring. Roots typically have a characteristic sshaped bend. Family: Brassicaceae (mustard).

Stems and leaves: First-year rosettes consist of 3–4 dark green, kidney-shaped 

leaves with scalloped edge margins only 2–4 inches off the ground. Flowering 

stems are light green, slightly ridged, hairless above and hairy below. Stem leaves 

are alternate, stalked, triangular to heart shaped and coarsely toothed, 1–31⁄2 inches 

long and 1-4 inches wide.

Flowers: Blooms April to May with white 4-petaled flowers in small tight clusters 

at the ends of the stalks.

Fruit and seeds: Dry fruit pods are 4 sided, erect to ascending, and thin, 1–5 

inches long and 0.05 inch (1.5 mm) wide. Pods initially look like green stem branches alternately whorled along the stalk, and ripen to tan and papery, exploding to 

fling tiny black seeds arranged in rows.

Habitat: Grows in forest understories, forest edges, shaded roadsides, riparian 

areas, flood plains, and trails. Shade tolerant.

Similar-looking plants: Native saxifrage species (Tellima grandiflora (Pursh) 

Douglas ex Lindl. and Tolmiea menziesii (Pursh) Torr. & A. Gray can be 

distinguished by the long hairs on their leaf stems and their green to pink flowers.

John M. Randall, The Nature Conservancy, Bugwood.org
64

FORBS

Common St. Johnswort 

HYPE

Institute for Applied EcologyInstitute for Applied Ecology

Norman E. Rees, USDA Agricultural 

Research Service, Bugwood.org

Institute for Applied Ecology
65

FORBS

Hypericum perforatum L. HYPE

Synonyms: St. Johnswort, St. John’s wort, Klamath weed.

Plant: Herbaceous perennial to 4 feet tall, with leaves covered with 

transparent dots and bright yellow 5-petaled flowers. Family: Clusiaceae 

(St. Johnswort).

Stems and leaves: Stems are highly branched near the top, slightly 2-ridged, 

hairless, often reddish and woody at the base. Leaves are opposite, stalkless, 

oblong, <1 inch long, covered in transparent dots visible when a leaf is held up 

to the light, and with rolled-under margin.

Flowers: Blooms June to September, with bright yellow flowers about 3⁄4 inch in 

diameter in clumps at the tips of stems. Flowers are 5-petaled, with scattered 

black dots along the margins of the petals, numerous yellow stamens, 

and 3 styles. First-year plants usually do not flower.

Fruit and seeds: Dry fruit (capsules) are oval, 3-chambered, and about 1⁄4 inch 

(5–10 mm) long, with 3 persistent styles and shiny black to brown densely pitted 

seeds.

Habitat: Disturbed roadsides, pastures, and rangeland. Tolerates light shade 

(e.g., open forest roads).

Similar-looking plants: Native St. Johnswort species (e.g., H. anagalloides 

Cham. & Schltdl. and H. scouleri Hook) occur in similar habitats but have at least 

one of the following characteristics: prostrate habit with matted aboveground 

runners (stolons), narrow and uniform (linear) to lance-shaped (lanceolate) 

leaves with pointy (acute) tips and often folded along the midvein, or 3-lobed 

capsules.

Common St. Johnswort 

Institute for Applied Ecology
66

FORBS

Sulfur cinquefoil

PORE5

Jennifer Anderson

© Steven J. Baskauf/TNC

Institute for Applied Ecology Institute for Applied Ecology
67

FORBS

Potentilla recta L. PORE5

Synonyms: Roughfruit cinquefoil, sulphur five-fingers.

Plant: Herbaceous perennial 1 to 3 feet tall, with palmate compound leaves 

(i.e., originating from a central point) and pale yellow 5-petaled flowers. Family: 

Rosaceae (rose).

Stems and leaves: One or more leafy stems rise from the woody root crown, with 

stems and leaves covered with stiff hairs. Leaves are palmately compound with 5 to 

7 toothed leaflets; the narrow teeth are half or slightly less than the width from 

edge to midvein. The central leaflet ranges 1–6 inches long.

Flowers: Blooms May to July with 5-petaled flowers 1⁄2–1 inch in diameter arranged 

in open, branched groups. Petals are pale yellow and heart shaped and sepals 

are about as long as the petals. Each flower has 25–30 stamens and often more 

than 50 pistils.

Fruit and seeds: Numerous seeds are produced per flower, egg shaped (obovate), 

slightly flattened, about 0.05 inch (1–1.5 mm) long, dark brown with pale netlike 

reticulate veins.

Habitat: Open forests, roadsides, pastures, and rangeland.

Similar-looking plants: There are numerous native nonweedy cinquefoils in our 

region of which slender cinquefoil (Potentilla gracilis Douglas ex Hook.) is most 

similar. However, unlike sulfur cinquefoil, slender cinquefoil rarely forms dense 

patches and has white woolly hair on the undersides of the leaves. Rough cinquefoil (Potentilla norvegica L.) is another nonnative cinquefoil often associated with 

cultivated land that has compound leaves with 3 leaflets.

Sulfur cinquefoil

Institute for Applied Ecology

Mary Ellen (Mel) Harte, Bugwood.org

Below: Slender cinquefoil (Potentilla gracilis Douglas ex Hook.).
68

FORBS

Herb-robert 

GERO

Institute for Applied EcologyInstitute for Applied Ecology

Katie Barndt
69

FORBS

Geranium robertianum L. GERO

Synonyms: Robert’s geranium.

Plant: Herbaceous annual or biennial to 2 feet 

tall, with dissected leaves, sticky, often red 

stems, small pink 5-petaled flowers, and a 

strong odor when crushed. Family: Geraniaceae (geranium).

Stems and leaves: Stems are often dark red and 

covered in white hairs that are glandular and feel 

sticky or oily. Leaves are dissected and appear 

to be compound with 3-5 lobed leaflets, and are 

light or dark green in color, turning reddish in the 

fall. Stems and leaves have a strong odor when 

crushed.

Flowers: Blooms April to September with 

5-petaled flowers in all shades of pink to purple 

(sometimes white), the petals are about 1⁄2 long 

(7–14 mm) and often have dark stripes, and the 

pollen is orange.

Fruit and seeds: Fruits are hairy and often have 

a long, straight, pointed beak.

Habitat: Forests, woodlands, roadsides, and 

riparian areas. Prefers shady areas.

Similar-looking plants: Shining geranium 

(Geranium lucidum L.) is a nonnative annual 

currently found in the northern Willamette Valley, 

Skagit County in Washington, and the San 

Francisco Bay area. Leaves differ from herbrobert in being shiny and lobed, not dissected. 

Dovefoot geranium (G. molle L.) is another 

nonnative in our region with simple lobed leaves 

with rounded teeth. Bleeding heart (Dicentra 

formosa (Haw.) Walp.) is a native with highly 

dissected, soft, hairless leaves that end in 

narrow oblong segments.

Herb-robert 

Institute for Applied Ecology

Below: Shining geranium (Geranium lucidum L.). Below: Dovefoot geranium (Geranium molle L.).
70

FORBS

Policeman’s helmet

IMGL

Institute for Applied Ecology

Amadej Trnkoczy

John Wright

Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
71

FORBS

Impatiens glandulifera Royle IMGL

Synonyms: Ornamental jewelweed, Impatiens roylei Walp.

Plant: Herbaceous annual that grows 3 to 10 feet tall, with simple leaves, and white 

to pink or purple flowers shaped like a British policeman’s helmet (fused tube 

with showy upper and lower lips at the opening). Family: Balsaminaceae (balsam).

Stems and leaves: Stems are straight and easily broken, with a purplish tinge. 

Stems and leaves are smooth and hairless. Leaves are opposite or whorled, and 

oblong to egg shaped, with serrated edges. 

Flowers: Blooms in midsummer with white to pink or purple flowers with 5 petals, 

5 fused stamens, and 2 sepals, and shaped like a British policeman’s helmet.

Fruit and seeds: (No information).

Habitat: Moist forests, roadsides, and riparian areas. Tolerates shade.

Policeman’s helmet

Institute for Applied Ecology

Jan Samanek, State Phytosanitary Administration, Bugwood.org
72

GRASSES

Medusahead

TACA8

Institute for Applied Ecology

Fred Hrusa

Fred Hrusa
73

GRASSES

Taeniatherum caput-medusae (L.) Nevski TACA8

Synonyms: Medusahead rye, Elymus caput-medusae L., Taeniatherum asperum auct. 

non (Simonkai) Nevski, Taeniatherum crinitum (Schreb.) Nevski var. caput-medusae

(L.) Wipff, many others (taxonomy unsettled).

Plant: Annual grass 6 to 24 inches tall forming dense stands, with spikes of longawned spikelets that often droop over horizontally when mature. Matures later than 

most other annual grasses and appears yellowish-green from a distance after other 

annual grasses have turned brown. Family: Poaceae (grass).

Stems and leaves: Stems are slender and round in cross section. Ligules are 

membranous (not fringed in hairs) and 0.08–0.2 inch (0.3–0.8 mm) long, auricles 

are present, and sheaths are open. Leaves are about 1/16 inch (1–3 mm) wide, 

4–12 inches long, smooth to softly hairy, and somewhat rolled.

Flowers and fruit: Spikelets grouped in a densely crowded bristly spike 1–4 inches 

long, with bristles (awns) >3⁄4 inch long. Spikelets are 3⁄4–11⁄2 inches long and flattened 

laterally. Old spikes remain intact long after the plant turns brown.

Habitat: Disturbed sites, rangeland, woodland, and chaparral.

Similar-looking plants: Hordeum and Elymus species are distinguished from 

medusahead by their 5-veined lemmas (medusahead lemmas are 3-veined) and 

main spike axes that typically break apart in fruit.

Medusahead

Fred Hrusa

John M. Randall, The Nature Conservancy, Bugwood.org
74

GRASSES

Cheatgrass

BRTE

Joseph M. DiTomaso Joseph M. DiTomaso

K. George Beck & James Sebastian, Colorado State University, Bugwood.org

Joseph M. DiTomaso
75

GRASSES

Bromus tectorum L. BRTE

Synonyms: Downy brome, chess, cheat, drooping brome, junegrass, Mormon oats, 

Schedonorus tectorum (L.) Fries, Anisantha tectorum (L.) Nevski, Zerna tectorum (L.) 

Panz., and others.

Plant: Annual grass 5–16 inches tall, maturing earlier than most other plants in 

spring, with sharp florets and straight awns. Family: Poaceae (grass).

Stems and leaves: Stems are round in cross section. Sheaths are closed (fused) 

for at least one-half the length and often hairy with a few long hairs, ligules are 

membranous and about 1/16 inch (1.5–3 mm) long with minutely jagged tips, and 

auricles are absent. Leaves are about 1⁄4 inch (1–6 mm) wide and hairy with a few 

long hairs at the base. Plants fade to a dingy tan after death and may be identified 

by their drooping habit and may remain intact for up to 3 years in desert areas.

Flowers and fruit: Spikelets grouped in a loose, open clump often drooping to 

one side 3–9 inches long, with the longest flower branches having 4–8 spikelets. 

Spikelets are slightly flattened. The bases of the florets are sharp, and lemmas are 

awned from the tip between 2 teeth, with the awns 1⁄3–3⁄4 inch (8–18 mm) long.

Habitat: Open disturbed areas, roadsides, woodland, open forest, and rangeland.

Similar-looking plants: Other annual Bromus species with sharp floret bases and 

straight awns including ripgut brome (B. diandrus Roth), red brome (B. rubens L.), 

and poverty brome (B. sterilis L.); ripgut is the only one that may have most or all 

flower branches that droop, but the awns are much longer than cheatgrass, being 

>1 inch long.

Cheatgrass

K. George Beck & James Sebastian, Colorado State University, Bugwood.org
76

GRASSES

Slender false brome

BRSY

Institute for Applied Ecology Institute for Applied Ecology

Institute for Applied Ecology Institute for Applied Ecology
77

GRASSES

Brachypodium sylvaticum (Huds.) Beauv. BRSY

Synonyms: Perennial false brome, Festuca sylvatica Huds.

Plant: Perennial bunchgrass growing in clumps 20 to 28 inches tall, with broad 

yellow green leaves with hairs along the edges. Family: Poaceae (grass).

Stems and leaves: Sheaths are open to the base, ligules are membranous and 

ciliate-hairy at the tip, and auricles are absent. Leaves are broad, flat, yellow green 

with hairs along the edges.

Flowers and fruit: Spikelets are not stalked, and spikes droop conspicuously.

Habitat: Roadsides, forest, and rangeland. Grows in deeply shaded and full light 

environments.

Similar-looking plants: Columbia brome (Bromus vulgaris (Hook.) Shear) is very 

similar but has spikelets that are stalked.

Slender false brome

Institute for Applied Ecology

Robert Soreng , USDA-NRCS PLANTS Database 
78

GRASSES

Jubata grass

COJU2

Joseph M. DiTomasoJoseph M. DiTomaso

Joseph M. DiTomaso

Joseph M. DiTomaso
79

GRASSES

Cortaderia jubata (Lem.) Stapf COJU2

Synonyms: Andean pampasgrass, cortaderia, selloana pampas grass, Cortaderia 

atacamensis (Phil.) Pilg., Gynerium jubatum, Gynerium quila Nees var. pygmaeum

Nees.

Plant: Large, densely tufted perennials 6–20 feet tall with long basal leaves and 

tall, showy, plumelike flowers. Family: Poaceae (grass).

Stems and leaves: Plants grow in large clumps with leaves >1⁄2 inch wide, with sharp 

serrated margins. Sheaths are open hairy, ligules are a ring of dense hairs about 0.1 

inch (2–3 mm) long, and auricles are absent.

Flowers and fruit: Blooms late summer to early fall, in large plumes 1–3 feet long, 

purple tinged to tan colored. Plumes from the previous year remain standing for about 

a year. Flower plumes are 1⁄4 to 1/5 the length of the plant and elevated above the 

leaves.

Habitat: Disturbed areas, dunes, roadsides, road cuts, and logged forests, particularly 

in areas with summer fog or ocean influence.

Similar-looking plants: Pampas grass (Cortaderia selloana (Schult. & Schult. f.) 

Asch. & Graebn.) is a nonnative that grows in similar environments, but unlike jubata 

grass the sheaths are hairless or sparsely hairy and the flower plumes are 1⁄2–1⁄4 the 

length of the plant.

Jubata grass 

John M. Randall, The Nature Conservancy, Bugwood.org

Below: Pampas grass (Cortaderia selloana

(Schult. & Schult. f.) Asch. & Graebn.)

Joy Viola, Northeastern University, Bugwood. org
80

GRASSES

Giant reed

ARDO4

David Graber

BonTerra Consulting Luigi Rignanese

Luigi Rignanese

Larry Allain, USDA-NRCS PLANTS Database
81

GRASSES

Arundo donax L. ARDO4

Synonyms: Bamboo reed, elephant grass, reed cane, reed grass, Spanish reed, giant 

cane, wild cane, Arundo glauca M. Bieb., Arundo latifolia Salisb., Arundo sativa Lam., 

Donax arundinaceus P. Beauv., Arundo versicolor Mill.

Plant: Large bamboolike plant in large clumps or hedges, 6–25 feet tall, with 

thick, well-developed creeping roots (rhizomes). Family: Poaceae (grass).

Stems and leaves: Canes are semiwoody, 1⁄2–11⁄2 inches thick, hollow between 

nodes, and mostly hairless. Canes erect, semiwoody, inflexible, about 1⁄2–11⁄2 inch 

thick, with long, hollow internodes. Sheaths are open, but tightly clasp the stem, 

ligules are membranous and fringed but only about 0.05 inch (1–2 mm) long, and the 

base of the leaves and auricles are yellowish with long hairs and clasp the stem. 

Leaves are flat, 1–3 feet long and 1–3 inches wide, with margins that are rough to the 

touch (scabrous), and grow alternately and on opposite sides of the stem in the same 

plane. Dead canes lose their leaves and become grayish and brittle.

Flowers and fruit: Blooms early spring to late fall in dense plumes 1–2 feet long, 

either open with ascending branches or closed with erect branches, and silvery cream 

colored to purplish or brown.

Habitat: Riparian areas, flood plains, and wet dunes.

Similar-looking plants: Common reed (Phragmites australis (Cav.) Trin. ex Steud.) 

is a smaller, widespread native that grows up to 13 feet tall. Unlike giant reed, it has 

blade bases and auricles that narrow gradually, stems <1⁄2 inch diameter, and ligules 

that consist of a membrane less than 0.05 inch (1 mm) long with hairs about 0.05 inch 

(1 mm) long.

Giant reed

Amadej Trnkoczy
82

GRASSES

Bulbous bluegrass

POBU

Joseph M. DiTomaso

Joseph M. DiTomaso

Joseph M. DiTomaso

Joseph M. DiTomaso Joseph M. DiTomaso

Joseph M. DiTomaso
83

GRASSES

Poa bulbosa L. POBU

Synonyms: Winter bluegrass.

Plant: Cool season perennial grass in dense clumps <2 feet tall, with bulbous-based

stems and dense flower clusters of leafy bulblets. Clumps enlarge around the edges 

from new bulbous-based stems. Family: Poaceae (grass).

Stems and leaves: Stems are thickened and bulblike at the base, and sometimes 

purplish near the base. Sheaths are open almost to the base and hairless, ligules are 

membranous and about 0.1 inch (2–4 mm) long, and auricles are not present. Leaves 

are ridged in the center, flat, and thin, usually <4 inches long and about 0.05 inch 

(1–2.5 mm) wide.

Flowers and fruit: Blooms in spring to early summer in 1–4 inches branched flower 

clusters, with spikelet flowers often developing into leafy bulblets. Spikelets usually have 4-6 bulblets that are about 0.1 inch (2 mm) long and dark purple.

Habitat: Woodlands, roadsides, pastures, and grassland. 

Similar-looking plants: Not readily confused with other weedy grasses.

Bulbous bluegrass

Sheri Hagwood, USDA-NRCS PLANTS Database

Richard Old, XID Services, Inc., Bugwood.org
84

acuminate—Leaf tip that tapers to a point; the sides are concave and 

tip is extended (fig. 2).

acute—Leaf tip that tapers to a point but is less tapering than 

acuminate; the angle of the sides is less than 90° (fig. 2).

alternate—Attachment of leaves to the stem in which one leaf is 

attached to each stem node (fig. 6).

annual—Plant whose life cycle is completed within a single year.

auricle—An ear-shaped appendage usually associated with the 

collar region of grasses (fig. 11) or the sheath of some submerged 

aquatic plants.

awn—A slender bristle attached to a tissue; usually refers to grass 

florets, primarily lemmas and glumes.

axil—The junction between the stem and the upper leaf base.

biennial—Herbaceous plant whose life cycle is completed within 2 

years. In the first year, plants germinate and typically exist as basal 

rosettes. In the second year, plants bolt, flower, and die.

bipinnate—Twice pinnate; leaves that are branched twice with 

leaflets on the second branch (fig. 5).

bract—A very reduced leaflike structure, usually associated with 

the base of a flower or inflorescence. 

bulbil (also called bulbel)—Small daughter bulbs that arise from 

the primary bulb.

calyx—Sepals collectively.

capsule—A dry fruit structure that opens by means of slits, lids, 

pores, or teeth to release its seeds.

Glossary

This glossary is composed of selected terms and drawings reproduced 

with permission from DiTomaso and Healy (2007). Figures 1 through 12 

illustrate the features used to distinguish species.

Figure 1—Leaf shapes.

caruncle—A spongy outgrowth of the seed coat. Can be a source of 

food for insects.

composite—A member of the Asteraceae (sunflower family); flower 

structure arranged in dense heads (fig. 10).

compound leaf—A leaf with two or more leaflets (fig. 5).
85

Figure 2—Leaf tips.

Figure 3—Leaf bases.

Figure 4—Leaf margins.

corolla—All the petals of a flower, collectively.

corymb—A flat-topped or rounded inflorescence that is unbranched or 

branched (compound corymb) with pedicels of varying lengths (fig. 8).

crenate—Leaf margin with shallow, rounded teeth (fig. 4).

cyathium—Inflorescence in members of the genus Euphorbia. 

Characterized by a pistillate flower and several staminate flowers within 

a cuplike involucre. The entire structure mimics a perfect flower.

cyme—A flat-topped or convex inflorescence type in which the flowers 

bloom from the center outward (fig. 8).

deciduous—Falling off, usually in reference to flower parts or leaves 

that fall off in the fall.

decurrent—Base of the leaf that extends down and is fused to the stem.

dentate—With spreading, pointed teeth.
86

Figure 5—Compound leaves.

Figure 6—Leaf arrangement.

Figure 7—Leaf surface and hair types.

Figure 8—Inflorescence types (larger circles indicate older flowers).
87

dioecious—Having male and female flowers on separate plants.

disk flower—Tubular flowers associated with the flower heads of 

many species in the Asteraceae (sunflower family) (fig. 10).

dissected—Leaves irregularly, sharply, or deeply cut but not compound 

(fig. 4).

drupe—A fleshy fruit that contains a single seed in a stony endocarp.

drupelet—A small drupe; usually refers to a cluster of drupelets that 

form a fruiting structure.

elliptic—Football-shaped; a flattened circle more than twice as long 

as wide (fig. 1).

endocarp—Inner layer of the walls of the ovary (pericarp).

entire—The smooth margin (lacking teeth) of a leaf (fig. 4).

evergreen—Having leaves that remain green on plant year-round; 

not deciduous.

floret—Usually, the flower (lemma and palea) of a grass (fig. 12). The 

combination of florets and glumes is a spikelet. Also used to describe 

small flowers in the Asteraceae (sunflower family).

fusiform—Having a spindle shape, wide in the middle and tapering 

toward the ends.

glaucous—A whitish or bluish green color owing to the deposition of 

waxes.

glume—Sterile bract or bracts (2) at the base of a grass spikelet (fig. 12).

indehiscent—Fruit that does not open to release seeds when mature.

inflorescence—Collected cluster or arrangement of flowers on a 

plant (fig. 8).

involucre—Group of bracts together beneath a flower or flower cluster.

lanceolate—Leaf shape that is narrow, widest in the middle, and tapering 

at both ends (fig. 1). Much longer than wide; narrower than fusiform.

leaflet—A subunit of a compound leaf (fig. 5).

lemma—Larger outer bract of a grass floret (fig. 12).

lenticel—A structure on the bark of woody plants that allows the 

exchange of gases.

ligulate flower—Flower type in the Asteraceae (sunflower family). 

Bilateral, fertile flower with long straplike corolla that is five-lobed. 

Only occurs when all flowers in a head are ligulate (fig. 10).

ligule—In grasses, the membranous projection at the inner junction of 

the blade and sheath (fig. 11).

linear—Long, narrow, and of uniform width (fig. 1).

membranous—Thin, soft, and transparent or translucent.

nutlet—A small nut that consists of a dry, thick-walled indehiscent 

structure with a single seed.

oblanceolate—Much longer than wide, and tapering at both ends. 

Similar to lanceolate but widest above the middle (fig. 1).

oblong—Much longer than wide; sides parallel and more or less 

rectangular (fig. 1).

obovate or obovoid—Widest at or above the middle and tapering at 

the base; egg shaped (fig. 1).

ocrea—A papery sheath that encloses the stem at the nodes and is 

formed from the fusion of two stipules. Typical of many members of 

the Polygonaceae (smartweed family).

ovary—Ovule-bearing portion of a pistil; develops into the fruit 

(figs. 9 and 12).

ovate or ovoid—Widest at or below the middle and tapering at the 

apex; egg shaped (fig. 1).

palea—Inner bract of a grass floret that is usually partially or totally 

enclosed by the lemma (fig. 12).

palmate—Branches, lobes, leaflets, or veins arising from a common 

point; similar to the palm of a hand (figs. 4 and 5).

panicle—Inflorescence branched more than once with flowers attached 

at the terminal end of the branchlets; branches can be short and give the 

inflorescence a spikelike appearance (fig. 8).
88

pappus—Modified calyx of the flower of species in the Asteraceae (sunflower family) that can take the form of bristles, feathery structures, scales, 

awns, or a low crown; typically facilitate wind or animal dispersal (fig. 10).

pedicel—Stalk of an individual flower (fig. 9).

peduncle—Stalk of a flower cluster, inflorescence, or flower head.

pericarp—Outer wall of the ovary.

petal—Individual part of the corolla, usually colored (fig. 9).

petiole—Stalk of a leaf; the area of the leaf below the blade.

phyllary—One of many bracts subtending the flower head of species in the 

Asteraceae (sunflower family). Collectively called an involucre (fig. 10).

Figure 9—General broadleaf flower structures.

Figure 10—Composite head and flower structures.

Figure 11—Grass stem structures.

Figure 12—General grass spikelet.
89

sheath—Generally, the base of a leaf that surrounds the stem. Nearly 

always present in grasses (fig. 11) but can be present on other monocots (e.g., cattails, sedges) and dicots (e.g., Apiaceae [carrot family] , 

Polygonaceae [knotweed family]).

silicle—Fruit type of many members of the Brassicaceae (mustard family). 

Characterized by being no more than twice as long as wide. Consists of 

two cells with a thin central septum. Seeds are released as the two halves 

of the fruit split, leaving the remaining septum.

simple—Not compound; single, undivided, and unbranched.

spike—An inflorescence with sessile flowers attached along an unbranched 

elongated rachis (fig. 8).

spikelet—Inflorescence of a grass or sedge that consists of glumes at the 

base and one or more sterile or fertile florets attached along an unbranched 

rachilla (fig. 12).

stamen—The male tissue of a flower that consists of filaments attached 

to anthers, which contain the pollen (fig. 9).

stigma—Upper region of the pistil that receives the pollen (figs. 9, 10, 

and 12).

stipule—Appendage at the base of the petiole or leaf; usually in pairs, 

sometimes thin and inconspicuous, other times leaflike.

stolon—Aboveground trailing shoot; roots form at the nodes.

style—Elongated structure above the ovary and below the stigma of the 

female portion of the flower (fig. 9).

tendril— Slender coiling structure that assists plants in climbing and 

supporting stems on other plants or structures. Usually found in the axil 

or tips of leaves.

umbel—Flower cluster in which the stalks or pedicels arise from a 

common point. Referred to as compound umbel when stalks of each 

cluster (peduncle) arise from a common point (fig. 8).

pinnate—Leaflets arranged on either side of a common axis (figs. 4 and 5).

pistil—Female structure of a flower; includes stigma, style, and ovary 

(fig. 9).

pod—Fruit of species in the Fabaceae (pea or bean family).

prickle—Sharp-pointed structure on a plant that usually originates as 

an outgrowth of the epidermis (e.g., hairs or rose thorns).

raceme—Elongated inflorescence with stalked flowers arising along the 

unbranched central axis (fig. 8).

rachilla—A small secondary axis to a rachis. Usually refers to the axis 

of a grass spikelet (fig. 12).

rachis—Central or main axis of an inflorescence or pinnately compound 

leaf (fig. 5).

ray flower—Flower type in the Asteraceae (sunflower family). Bilateral 

sterile or female flower with long straplike corolla that has up to three 

lobes. Associated with flower heads that also contain disk flowers (fig. 10).

receptacle—Tissue of the inflorescence where the flower parts arise, as in 

species in the Asteraceae (sunflower family), Ranunculaceae (buttercup 

family), Rosaceae (rose family), and others (fig. 9).

rosette—Cluster of leaves arising from a very short stem at the surface of 

the soil; lacking an erect stem.

rhizomes—a horizontal underground stem that contains nodes and 

reduced scaly leaves.

scabrous—Rough to the touch owing to the presence of short, stiff hairs 

(fig. 7).

sepal—One of the outer whorls of a flower, usually green; collectively 

known as the calyx (fig. 9).

serrate—Having sharp teeth directed forward, as in the teeth on a leaf 

margin (fig. 4).

sessile—Lacking a petiole at the base of a leaf, or lacking a pedicel at the 

base of a flower (fig. 3).
90

Metric Equivalents

English units Metric units

1 inch (in) = 25.4 millimeters (mm)

1 inch (in) = 2.54 centimeters (cm)

1 foot (ft) = 0.3048 meter (m)

References

Blossey, B. 1999. Before, during and after: the 

need for long-term monitoring in invasive 

plant species management. Biological 

Invasions 1: 301–311.

Boersma, P.D.; Reichard, S.H.; Van Buren, 

A.N.; Gamboa, R.L., eds. 2006. Invasive 

species in the Pacific Northwest. Seattle, WA: 

University of Washington Press. 285 p.

California Department of Food and 

Agriculture. 2008. Pest ratings of noxious 

weed species. Sacramento, CA: California 

Department of Food and Agriculture. http://

www.cdfa.ca.gov/phpps/ipc/weedinfo/winfo_

list-pestrating.htm. (November 4, 2008).

California Invasive Plant Council. 2006. 

California invasive plant inventory. CalIPC Publication 2006-02. Berkeley, CA: 

California Invasive Plant Council. http://

www.cal-ipc.org/ip/inventory/index.php. 

(November 4, 2008).

DiTomaso, J.M.; Healy, E.A. 2007. Weeds 

of California and other Western States. 

Agriculture and Natural Resources 

Publication 3488. Oakland, CA: University 

of California. 2 vols.

Gray, A.N.; Azuma, D.L. 2005. Repeatability 

and implementation of a forest vegetation 

indicator. Ecological Indicators. 5: 57–71.

Heinz Center (H. John Heinz III Center for 

Science Economics and the Environment). 

2002. The state of the Nation’s ecosystems: 

measuring the lands, waters, and living 

resources of the United States. New York: 

Cambridge University Press. 270 p.

Hitchcock, C.L.; Cronquist, A.; Ownbey, M.; 

Thompson, J.W. 1969. Vascular plants of the 

Pacific Northwest. Publications in Biology 17. 

Seattle, WA: University of Washington Press. 

Hurteau, M.D.; Briggs, R. 2003. Common 

yarrow—Achillea millefolium L. Plant fact 

sheet. Baton Rouge, LA: National Plant Data 

Center. http://plants.usda.gov/factsheet/pdf/

fs_acmi2.pdf. (May 12, 2009).

Journal of Forestry. 1995. Statement on 

criteria and indicators for the conservation 

and sustainable management of temperate and 

boreal forests. Journal of Forestry. 93: 18–21.

Miller, J.H. 2003. Nonnative invasive 

plants of southern forests: a field guide for 

identification and control. Gen. Tech. Rep. 

SRS-62. Asheville, NC: U.S. Department 

of Agriculture, Forest Service, Southern 

Research Station. 93 p.

Mooney, H.A.; Hobbs, R.J. 2000. Invasive 

species in a changing world. Washington, 

DC: Island Press.

Morse, L.E.; Randall, J.M.; Benton, N.; 

Hiebert, R.; Lu, S. 2004. An invasive 

species assessment protocol: evaluating nonnative plants for their impact on biodiversity, 

version 1. Arlington, VA: Natureserve. 

http://www.natureserve.org/library/

invasiveSpeciesAssessmentProtocol.pdf. 

(March 2, 2009).

Murai, M. 1999. Understanding the invasion 

of Pacific Northwest forests by English ivy 

(Hedera spp., Araliaceae). Seattle, WA: 

University of Washington. 82 p. M.S. thesis.

National Research Council Committee 

to Evaluate Indicators for Monitoring 

Aquatic and Terrestrial Environments. 

2000. Ecological indicators for the Nation. 

Washington, DC: National Academy Press. 
91

Oregon Department of Agriculture. 2008. 

Noxious weed policy and classification 

System 2008. Salem, OR: Oregon 

Department of Agriculture. http://www.

oregon.gov/ODA/PLANT/WEEDS/

lists.shtml. (November 4, 2008).

Oregon Invasive Species Council. 2008. 100 

most dangerous invaders to keep out. Salem, 

OR: Oregon Invasive Species Council. http://

www.oregon.gov/OISC/most_dangerous.

shtml. (November 4, 2008).

Pimentel, D.; Zuniga, R.; Morrison, D. 2005. 

Update on the environmental and economic 

costs associated with alien-invasive species 

in the United States. Ecological Economics. 

52: 273–288.

Schulz, B. 2003. Forest inventory and analysis: 

vegetation indicator. FIA Fact Sheet Series. 

Washington, DC: USDA Forest Service, 

Forest Inventory and Analysis Program. 

http://fia.fs.fed.us/library/fact-sheets/p3-

factsheets/vegetation.pdf. (October 12, 2008).

U.S. Department of Agriculture, Forest 

Service. 2006. 2006 field instructions for the 

annual inventory of Washington, Oregon, 

and California. Portland, OR: USDA Forest 

Service, Pacific Northwest Research Station. 

http://www.fs.fed.us/pnw/fia/local-resources/

pdf/field_manuals/2006_field_manual.pdf. 

(June 4, 2006).

U.S. Department of Agriculture, Natural 

Resource Conservation Service [USDA 

NRCS]. 2009. The PLANTS Database. 

Baton Rouge, LA: National Plant Data Center. 

http://plants.usda.gov. (August 13, 2009).

Vitousek, P.M.; D'Antonio, C.M.; Loope, 

L.L.; Westbrooks, R. 1996. Biological 

invasions as global environmental change. 

American Scientist. 84: 468–478.

Washington State Noxious Weed Control 

Board. 2008. Washington State noxious 

weed list. Olympia, WA: Washington State 

Department of Agriculture. http://www.nwcb.

wa.gov/weed_list/weed_list.htm. (November 

4, 2008).

Wilson, L.M. 2006. Key to identification of 

invasive and native hawkweeds (Hieracium

spp.) in the Pacific Northwest. Kamloops, 

BC: British Columbia Ministry of Forest 

and Range, Forest Practices Branch. 21 p. 

http://www.for.gov.bc.ca/hra/Publications/

invasive_plants/Hawkweed_key_PNW_2007.

pdf. (June 29, 2009).

Wisehart, L.; Kaye, T.; Kirkland, M. 2008. 

Field guide to weeds of the Willamette Valley. 

Corvallis, OR: Institute for Applied Ecology. 

http://www.appliedeco.org. (May 10, 2009).

Zika, P.F.; Alverson, E.R. 2005. Notable 

collections. Madroño. 52: 270–274.

Pacific Northwest Research Station

Web site http://www.fs.fed.us/pnw/

Telephone (503) 808-2592

Publication requests (503) 808-2138

FAX (503) 808-2130

E-mail pnw_pnwpubs@fs.fed.us

Mailing address Publications Distribution 

Pacific Northwest Research Station

P.O. Box 3890

Portland, OR 97208-3890