Noxious Weeds of Klamath County - Rabe Consulting

Noxious Weeds of
Klamath County
Field Identification Handbook

Noxious Weeds
of
Klamath County
A Field Identification Guide
Prepared By:
Andrea Rabe
Michael Calonje
Christopher Calonje

A special acknowledgement to
Klamath County Commissioners
Al Switzer, John Elliot and Bill Brown
For providing funding for publication costs through
PL 06-393 Title III
“Secure Rural Schools and Community Self-
Determination Act of 2000”
Klamath County wishes to acknowledge all private,
state and federal partners who are assisting with the
campaign against noxious weeds.

Introduction
Invasive weed species are one of Klamath County’s
greatest threats. These unwelcome plants are not
only major pests of agriculture, they also threaten the
health of all other natural ecosystems. The invasion
of noxious weeds reduces biological diversity,
impacts threatened and endangered species, reduces
or eliminates native vegetation, destroys recreational
environments, and costs Oregonians millions of
dollars each year.
The primary emphasis of this weed book is to
increase public awareness. Being able to recognize
and identify noxious invaders is the first step in
control and/or eradication. Early detection is the
key to having a successful weed program. We hope
people in this area will use this book as a field guide
to identify and report all occurrence of these weeds
and what measures were used for control. Using a
cooperative effort, we will ensure that our County
will not let these weeds destroy all that we value.
Use Pesticides Safely!!
•Wear protective clothing and safety devices as
recommended on the label. Bathe after each use.
•Read pesticide label - even if you have previously
used the pesticide. Precisely follow label instructions.
•Be cautious when you apply pesticides. Know your
legal responsibility as a pesticide applicator. You may
be liable for injury or damage resulting from your
pesticide use.
3

Table of Contents
BORAGE FAMILY
Hound’s tongue........................................................6
BUTTERCUP FAMILY
Creeping buttercup..................................................8
CALTROP FAMILY
Puncturevine...........................................................10
DODDER FAMILY
Field dodder............................................................12
FIGWORT FAMILY
Dalmatian toad-flax...............................................14
GRASS FAMILY
Matgrass.................................................................16
LEGUME FAMILY
Scotch broom.........................................................18
LOOSESTRIFE FAMILY
Purple loosestrife...................................................20
MINT FAMILY
Mediterranean sage.................................................22
MORNING-GLORY FAMILY
Field bindweed.......................................................24
MUSTARD FAMILY
Hoary cress............................................................26
Dyer’s woad...........................................................28
Perennial pepperweed............................................30
PARSLEY FAMILY
Western waterhemlock...........................................32
Poison hemlock......................................................34
SPURGE FAMILY
Leafy spurge..........................................................36

Myrtle spurge.........................................................38
ST. JOHNSWORT FAMILY
St. Johnswort..........................................................40
SUNFLOWER FAMILY
Russian knapweed..................................................42
Musk thistle............................................................44
Diffuse knapweed..................................................46
Spotted knapweed..................................................48
Meadow knapweed................................................50
Yellow starthistle....................................................52
Squarrose knapweed..............................................54
Skeletonweed.........................................................56
Canada thistle.........................................................58
Scotch thistle..........................................................60
Tansy ragwort.........................................................62
Spiny cocklebur......................................................64
Glossary....................................................................66
References.................................................................68
Noxious Weed Survey Form ....................................70

Borage Family (Boraginaceae)
Hound’s tongue
Cynoglossum officinale L.
© Br. Alfred Brosseau, Saint Mary’s College
6

Description: Biennial or short-term perennial
standing 1 to 4 feet tall. Soft, hairy leaves are
narrowly elliptic and 3 to 8 inches long. Inflorescence
more or less overlapping leaves with leaf-like bracts
and reddish-purple flowers. Fruits are nutlets with
barbed hooks and raised edges that attach readily to
animal fur and clothing.
Habitat: Thought to have originated in western
Asia and eastern Europe, hound’s tongue has spread
throughout all but six states in the contiguous United
States. It is found in dry habitats in open woods and
disturbed areas such as fields and roadsides.
Economics: Plants can cause liver damage or failure
in horses and cattle when grazed directly or if cut and
dried with harvested hay.
Left picture from Weeds of the West - used with permission , right picture © 2001 CDFA
7

Buttercup Family (Ranunculaceae)
Creeping buttercup
Ranunculus repens L.
8
© 2005 Michael Calonje

Description: Perennial plants which spread along
ground. Stems are hairy. Leaves are hairy with
toothed margins and 3 parts. Flowers sit on long
stems. Flowers are few and showy yellow. Seedheads
contain about 12 seeds which are 1/8 inch long, flat,
and round.
Habitat: Originally ornamental from Europe. Plants
occur in moist areas in pastures.
Economics: Creeping Buttercup is a very aggressive
plant in most pasture lands, also toxic to cattle when
ingested.
9
© 2005 Michael Calonje

Caltrop Family (Zygophyllaceae)
Puncturevine
Tribulus terrestris L.
0
© 2005 Michael Calonje

Description: Annual plants are mat-forming with
sprawling stems 1/2 to 5 feet long. Opposite hairy
leaves have 4 to 8 pairs of aval leaflets. Yellow
flowers have petals and are 1/2 inch long with 2 to
4 sharp spines. When mature, seeds break into five
parts.
Habitat: Native to the Mediterranean. Plants occur
in pastures, cultivated fields, ditchbanks, roadsides,
wastelands, and other disturbed areas. Plants prefer
sandy soil. Other common names include goathead,
sandbur, or caltrop.
Economics: The hard, spiny burs may be injurious to
livestock, stick painfully in bare feet, and cause flats
in bicycle tires and four-wheelers.
© 2005 Michael Calonje

Dodder Family (Cuscutaceae)
Field dodder
Cuscuta campestris Yuncker
12
Top and bottom images © G.D. Carr

Description: Parasitic annual with yellow threadlike
stems. Leaves reduced to threadlike scales.
Numerous white to pink flowers occur in compact
clusters and have five parts. Flowers from July to
October. Seeds are 2 to 4 in globular capsules, small,
oval, and gray to red.
Habitat: Many broadleaf plants serve as hosts.
Common hosts are alfalfa and clover.
Economics: A problem plant in the West where seeds
can lay dormant in the soil for many years. Dodder
infestations reduce the hardiness of host plants thus
reducing economic value.
3

Figwort Family (Scrophulariaceae)
Dalmatian toadflax
Linaria genistifolia (L.) Miller
ssp. dalmatica (L.) Maire & Petitm.
© 2005 Michael Calonje

Description: Perennial plants are robust and up to 4
feet tall. Blue green leaves are waxy and heart-shaped
clasping stems. They are less than 2 inches long,
alternate, and entire. Yellow flowers are two-lipped
with orange hairy centers. Long spurs give flowers
resemblance of snapdragon flowers. Flowers occur
on upper stems from July to August. Plants spread
by creeping roots or irregular seeds from 2-celled
capsules.
Habitat: Originally an ornamental from the
Mediterranean. Plants are located in disturbed areas,
along roadsides, and in rangelands. This nonpalatable
plant prefers dry areas.
Economics: An aggressive plant that may crowd out
desirable vegetation. Due to its deep root system this
plant is very hard to control.
© 2005 Michael Calonje

Grass Family (Poaceae)
Matgrass
Nardus Stricta L.
6
© J. E. Gómez / Waste magazine

Description: A tussock-forming perennial plant 4 to
16 inches tall. Leaves are dark green to bluish, hard
and bristle-like, up to 1/4 inch wide and folded tightly
along the midrib. Flower spikes are single, narrow
and one-sided. Spikelets 1/5 to 1/3 inches long with
single florets tipped by short, straight awns. Anthers
are yellow at first, turning white with age.
Habitat: Originally from Eastern Europe but now
widely distributed in several continents, preferring
open areas such as grasslands and pastures.
Economics: An unpalattable species for livestock
that may outcompete other grasses in grazing areas.
Reproduces by clinging to mud carried in hooves of
livestock animals.
17
© J. E. Gómez / Waste magazine

Legume Family (Fabaceae)
Scotch broom
Cytisus scoparius (L.) Link
Top picture © Br. Alfred Brosseau, Saint Mary’s College, bottom left © 2005 Brianna
M. Richardson, bottom right Charles Webber © California Academy of Sciences
18

Description: Woody perennial shrub up to 10 feet
tall. Branches are dark green, mostly erect, and
appear mostly naked. Leaves are mostly 3-parted
with entire leaflets 1/5 to 4/5 inches long. Flowers are
yellow and abundant. Seed pods are flat, brownish
black and hairy on the margins only. Flowers in late
spring and early summer.
Habitat: Originally from Europe, the plant was
introduced as an ornamental to the Pacific coast,
where it has become a widespread pest. It invades
open and disturbed areas such as pastures and
cultivated fields, grasslands, logged areas, roadsides,
and waterways.
Economics: Scotch broom spreads aggressively due
to its tolerance of a wide range of soil conditions, its
ability to fix nitrogen, and its abundant production
of long-lasting seeds. It displaces native vegetation,
creates a fire hazard, and diminishes the value of
rangeland as it is slightly toxic and unpalatable to
livestock.
9

Loosestrife Family (Lythraceae)
Purple loosestrife
Lythrum salicaria L.
Picture from Weeds of the West - used with permission
20

Description: Perennial with erect stems 2 to 6 feet
tall. Leaves are lance-shaped, simple, entire, and
opposite or whorled. Flowers are rose-purple with
5-7 petals and less than 1/2 inch long. Flowers cluster
in spikes on terminal stems. Flowers from August to
September.
Habitat: Found in moist, marshy areas, ponds,
stream banks, meadows, and ditches. Sometimes
growing so dense they impede water flow in ditches.
Originally cultured as an ornamental in Europe
Economics: Because of its ability to out-compete
other desirable vegetation, purple loosestrife
infestations reduce wildlife habitat, food and cover
for waterfowl, and reduces wetland biodiversity.
Left and right pictures © 2005 Louis-M. Landry
21

Mint Family (Lamiaceae)
Mediterranean sage
Salvia aethiopsis L.
22
© 2001 CDFA

Description: Biennial which grows 2 to 3 feet tall.
Gray woolly leaves are coarsely toothed. First year
rosette is up to 2 feet in diameter. Second year plants
bolt with branched stems. Lower leaves are up to
one foot long, while upper leaves are small. Yellowwhitish
flowers are profusely clustered along stem.
Flowers occur from June to August. Seeds are four
nutlets per flower. When mature, plant resembles a
tumbleweed.
Habitat: Originally from Europe this plant is found
in pastures, meadows, range sites, and other open
areas.
Economics: A single plant can produce thousands
of seeds which are deposited when winds blow the
tumbleweed-like cane across landscapes.
23
© 2005 Michael Calonje

Morning-glory Family (Convolvulaceae)
Field bindweed
Convolvulus arvensis L.
24
© 2005 Michael Calonje

Description: Perennial plant with stems creeping 1
to 4 feet. Plants form entangled mat. Alternate leaves
are arrowhead shaped. White to pinkish flowers
are trumpet shaped and 1 inch in diameter. Flowers
from June to September. Seeds occur 4 per capsule.
Capsules are small and round.
Habitat: Native to Europe. Plants are located in
disturbed areas such as cultivated fields and waste
places. Plants are adaptable and may occur up to
10,000 feet elevation.
Economics: A troublesome pest in agriculture and
extremely hard to control due to its deep taproot (up
to 10 feet) and long viability of its seed (50 years).
25
© 2005 Michael Calonje

Mustard Family (Brassicaceae)
Hoary cress
Cardaria draba (L.) Desv.
© Br. Alfred Brosseau, Saint Mary’s College,
26

Description: Perennial standing up to 2 feet tall.
Leaves are blue-green and lanceolate. Lower leaves
are stalked with upper leaves being two-lobed and
clasping stem. Small white flowers occur in flat
clusters at top of stems. Flowers have 4 petals and
occur from April to July. Two reddish-brown seeds
are divided by a papery division in heart-shaped
capsules. Plant spreads by deep roots and seeds.
Habitat: Native to Europe. Plants are located in
disturbed alkaline soils along stream banks and
waterways.
Economics: Plants are very competitive and form
monocultures, thereby reducing desirable vegetation
and wildlife habitat.
27
© 2005 Luigi Rignanese

Mustard Family (Brassicaceae)
Dyer’s woad
Isatis tinctoria L.
28
© 2005 Michael Calonje

Description: Winter annual, biennial, or short lived
perennial. Growing 1 to 4 feet tall. Leaves are bluegreen,
alternate, oblong, basal, and have a white vein
on top surface. Small yellow flowers occur in dense
flat-topped clusters from April to June. Large tap
roots extend up to 5 feet and can resprout. Seeds are
purple-brown with one per pod.
Habitat: Native to Europe. Plants inhabit grain
fields, pastures, alfalfa, waste areas, roadsides,
railroads, and fence lines.
Economics: The presence of dyer’s woad in hay
decreases feed and economic values. It also occurs
in dense infestations which out-compete desirable
vegetation.
Left picture © 2005 Michael Calonje, Right picture © 2001 CDFA
29

Mustard Family (Brassicaceae)
Perennial pepperweed
Lepidium latifolium L.
30
© 2005 Michael Calonje

Description: Perennial plants stand 1 to 6 feet tall.
Leaves are entire to toothed, lanceolate, and gray to
bright green. Larger leaves occur at plant base. Small
white flowers form dense clusters on top of branches
from June to August. 2 red-brown seeds per silicle.
Seeds are round, flat, hairy, and 1/16 inch in diameter.
Plants have robust and deep spreading root system.
Habitat: Native to southern Europe and western
Asia. Plants are found in waste areas, ditches, wet
areas, roadsides, croplands, waterways, and dry
habitats including cuts and fills.
Economics: Plants out-compete crops and native
vegetation forming monocultures which are very
hard to control due to its profuse seed production and
extensive creeping root system.
3
© 2005 Michael Calonje

Parsley Family (Apiaceae)
Western waterhemlock
Cicuta douglasii (DC.) J. Coulter & Rose
32
© 2005 Michael Calonje

Description: Perennial with erect stems 3 to 7 feet
tall. Leaves are alternate with one per node and
pinnately divided. Small white flowers cluster in a
compound umbel at apex of stalk. Flat umbels occur
from May to July. Seeds are two per flower, kidney
shaped, ridged, and brown. Taproot is horizontally
divided.
Habitat: Native to intermountain region of North
America. Plants are common in wet areas especially
untilled areas, pastures, stream edges, and irrigation
canals.
Economics: Western waterhemlock is the most
poisonous plant in North America. It is toxic to all
classes of animals and humans, acting directly on the
nervous system.
33
© 2005 Michael Calonje

Parsley Family (Apiaceae)
Poison hemlock
Conium maculatum L.
3
© 2005 Michael Calonje

Description: Biennial growing 6 to 8 feet tall. Erect,
stout stems have distinct ridges and purple spots.
Leaves are shiny green, divided three to four times
with segmented leaflets being 1/8 to 1/4 inch long.
White flowers are located in numerous umbrellashaped
clusters on each stalk. Paired seeds are light
brown, ribbed, and 1/8 inch long.
Habitat: Native to Europe. Plants occur in edges of
pastures and cropland. Plants tolerate poorly drained
soils along streams and ditches.
Economics: All parts of the plant are toxic to humans
and animals. May cause death if ingested in high
enough doses.
3
© 2005 Michael Calonje

Spurge Family (Euphorbiaceae)
Leafy spurge
Euphorbia esula L.
36
© 2005 Michael Calonje

Description: Glabrous perennial standing 2 to 3 feet
tall. Plants have milky juice and large root reserves.
Leaves are narrow, alternate, and 1 to 4 inches in
length. They tightly cluster around stems. Small
yellow-green flowers are subtended by two bright
yellow-green, heart shaped bracts. Flowers occur
from June to July. Plants spread by seeds from 3celled
capsules or creeping roots.
Habitat: Leafy spurge grows in a wide range of
habitats, but occurs most commonly in pastureland,
rangeland, woodland, prairies, roadsides, stream and
ditchbanks, and waste sites.
Economics: Plants cause irritation in digestive
tracts of cattle and may cause death in horses. It
also reduces grazing productivity, crowds out native
vegetation, and is very difficult to eradicate.
37
© 2005 Michael Calonje

Spurge Family (Euphorbiaceae)
Myrtle spurge
Euphorbia myrsinites L.
Top Picture © Krzysztof Kozminski, bottom picture © Kelly Uhing
38

Description: Perennial forb 4 to 8 inches tall with
fleshy trailing stems spreading up to 18 inches.
Leaves are oval, blue-green, fleshy, and are arranged
alternately in close spirals around stems. Stems
emerge from a central taproot in early spring.
Flowers are greenish and inconspicuous, subtended
by a showy yellow bract. Flowers appear from early
spring to mid summer.
Habitat: Native to Eurasia and brought to the United
States as an ornamental, it inhabits dry rocky areas in
disturbed areas.
Economics: Leaves, stems and roots exude an
irritating milky sap that when broken can produce
redness, swelling, and blistering on skin. The plant is
slightly toxic, and may cause nausea, vomiting and
diarrhea when ingested.
39

St. Johnswort Family (Hypericaceae)
St. Johnswort, Klamath weed
Hypericum perforatum L.
0
© 2005 Michael Calonje

Description: Perennial growing 1 to 3 feet tall.
Stems are erect with 2 ridges and many rust colored
branches. Opposite, oblong, entire leaves exhibit tiny
“windows”. Leaves are less than 1 inch long. Bright
yellow flowers are numerous in tight clusters at top
of stems. Flowers have 5 petals, numerous stamens in
three clusters, and are 3/4 inch in diameter. Flowers
occur from June to September. Seeds from 3-celled
capsules and short runners allow spread of plant.
Habitat: Native to Europe. Plant is located in sandy
to gravelly soils in disturbed areas and along roads.
Economics: This plant is dangerous at all stages of
growth. When ingested, it causes sun sensitivity and
skin irritation. It is also an aggressive plant, growing
in dense patches.
Left picture © 2005 Michael Calonje, Right picture © www.nwcb.wa.gov

Sunflower Family (Asteraceae)
Russian knapweed
Acroptilon repens L.
Copyright © Province of British Columbia. All rights reserved. Reprinted with
permission of the Province of British Columbia.
42

Description: Perennial, forms dense colony with
shoots from spreading roots. Plants are erect, openlybranched,
and 18 to 36 inches tall. Lower leaves are
deeply divided and 2 to 4 inches long. Upper leaves
are entire to serrate. Flower heads are 1/4 to 1/2 inch
in diameter and pink to lavender in color. Occur
in clusters on ends of branches. Pearly bracts have
rounded or pointed papery margins. Flowers occur
from June to September. Seeds are small, 1/4 to 1/8
inch long with numerous white hairs.
Habitat: Native to central Asia. Plants are found in
cultivated fields, orchards, pastures, roadsides, and
rangelands.
Economics: Once established, this plant is very hard
to control or eradicate. By forming dense colonies it
will out-compete native vegetation and crops.
3
© 2001 CDFA

Sunflower Family (Asteraceae)
Musk thistle
Carduus nutans L.
© 2005 Michael Calonje

Description: Biennial and sometimes winter annual.
Growing up to 6 feet tall. Dark green leaves have
white ventral vein and are deeply lobed with spiny
margins. First year leaves form rosette, with bolting
and flowers second year. Flower heads are solitary,
deep rose violet, and occur on tops of stems. Seeds
are yellowish brown with plume of white hairs.
Habitat: Native to southern Europe and western
Asia. Plants are located in pastures, rangelands,
forest lands, and along roadsides, ditch banks, stream
banks, and grain fields.
Economics: Musk thistle infestations can pose a
major problem by out-competing more desirable
vegetation for moisture and nutrients. It can also
reduce forage for wildlife and livestock.
© 2005 Michael Calonje

Sunflower Family (Asteraceae)
Diffuse knapweed
Centaurea diffusa Lam.
6
© 2005 Michael Calonje

Description: Annual to short-lived perennial. Plants
are diffusely branched and 1 to 2 feet tall. Stems are
rough. Leaves are pinnately divided. Flower heads
are numerous and narrow. Flowers are white to rose
with bracts divided like teeth and tipped with slender
spine. Flowers occur July to September.
Habitat: Native to Mediterranean region. Plants
invade roadsides, waste areas, dry rangelands, and
pastures.
Economics: This tough competitor rapidly invades
and dominates disturbed sites. Plants will outcompete
and exclude desirable vegetation.
Left picture © 2005 Michael Calonje, right picture © 2001 CDFA
47

Sunflower Family (Asteraceae)
Spotted knapweed
Centaurea maculosa Lam.
48
© 2005 Michael Calonje

Description: Biennial to short-lived perennial
standing erect from 1 to 3 feet tall. Narrow basal
leaves are up to 6 inches long and entire or pinnately
parted. Stem leaves are finely divided when mature.
Pink-purple to cream solitary flower heads occur on
branch ends. Bracts have stiff tips with dark fringes.
Flowers occur from June to October. Seeds are 1/8
inch long with tufts of persistent bristles.
Habitat: Native to Europe. Plants are located in
disturbed areas along roadsides and waste areas. They
also occur in dry to moist rangelands.
Economics: Invasions of spotted knapweed reduce
grazing forage for wildlife and livestock. These
plants may also excrete a chemical which discourages
other vegetative growth.
© 2005 Michael Calonje
9

Sunflower Family (Asteraceae)
Meadow knapweed
Centaurea pratensis Thuill.
0
© www.forestryimages.org, Cindy Roche

Description:
A perennial growing 20 to 40 inches tall. Lower
leaves are up to six inches long and can be entire,
coarsely lobed, or toothed. The middle leaves are
lance-shaped and entire or shallowly lobed. The
uppermost leaves are smaller and not lobed. Pink to
purplish-red flowerheads are globe-shaped and occur
at the end of branches. Bracts are roundish, deeply
fringed, and light to dark brown. Flowers from July to
September. Considered to be a hybrid between black
knapweed (Centaurea nigra) and brown knapweed
(Centaurea jacea), so traits may be highly variable.
Habitat:
Native to Europe. It infests roadsides, pastures,
meadows, and waste areas.
Economics:
An aggressive, invasive species that outcompetes
native vegetation and crops, thereby reducing forage
for livestock and wildlife.
© www.forestryimages.org, Cindy Roche

Sunflower Family (Asteraceae)
Yellow starthistle
Centaurea solstitialis L.
52
© 2005 Michael Calonje

Description: Annual standing 2 to 3 feet tall. Rigid
branches are winged and hairy. Basal leaves are
deeply lobed while upper leaves are entire and
sharply pointed. Flower heads are yellow, solitary on
branch tops, and exhibit straw-colored thorns up to
3/4 inch long. Fruits are dark without bristles.
Habitat: Native to Europe. Plants grow on various
soil types usually along roadsides or in waste areas.
Economics: Invasions of this weed will decrease
rangeland productivity, out-compete native vegetation
and can cause “chewing” disease in horses. A severe
threat due to its high adaptability.
3
© 2005 Michael Calonje

Sunflower Family (Asteraceae)
Squarrose knapweed
Centaurea virgata Lam.
Top Picture © Steve Dewey, Bottom picture © 2001 CDFA

Description: Perennial stands 1 to 1 1/2 feet tall
and is highly branched. Leaves are deeply divided,
upper leaves are small and gray. Flower heads are
numerous with 4 to 8 small rose to pink flowers.
Bract tips bend back or spread with the terminal
spines being longer than the lateral spines on each
bract. Seed heads break away when mature. Flowers
occur from June to August. Plants have large taproot.
Habitat: Plants, originally from Asia, inhabit dry
disturbed, sandy, or cinder soils. Different from
diffuse knapweed because plants have bracts which
bend back and heads with loose seeds.
Economics: Out-competes and replaces native
vegetation. Reduces rangeland productivity, reducing
wildlife and livestock forage.

Sunflower Family (Asteraceae)
Rush skeletonweed
Chondrilla juncea L.
Picture from Weeds of the West - used with permission
6

Description: Perennial growing 1 to 4 feet tall.
Lower 4 to 6 inches of stems have downwardly bent
coarse hairs. Leaves form basal rosette and wither
as flower develops. Leaves are toothed. Flower
heads are scattered on branches with 7 to 15 yellow,
strap-shaped flowers. Flowers from mid-July through
September. Seeds are pale brown, ribbed, and 1/8
inch long. Plants have extensive root system and
milky latex sap.
Habitat: Native to Europe. Plants inhabit welldrained
soils along roadsides, in grain fields, pastures,
and rangelands. Plants prefer disturbed sites.
Economics: This plant spreads aggressively through
development of daughter rosettes, seeds, or buds
on root fragments, A difficult weed to control, it
severely reduces forage for wildlife and livestock.
Left picture © 2001 CDFA, Right picture © G.D Carr
57

Sunflower Family (Asteraceae)
Canada thistle
Cirsium arvense (L.) Scop.
58
© 2005 Michael Calonje

Description: Perennial with 1 to 4 foot stems which
are ridged and branched. Leaves are alternate,
oblong or lanceolate, and divided into spine-tipped
irregular lobes. Flowers are purple, occur in heads
1/2 to 3/4 inch in diameter, and have spineless bracts.
Flowers occur July to August. Fruits are 1/8 inch
long, flat, brown, and have tufts of hairs on top.
Colonies spread through seeds and extensive root
systems.
Habitat: Native to southeastern Eurasia. Differs
from other thistles because it has male and female
plants. Occurs in various habitats in pastures,
roadsides, and rangelands.
Economics: One of the most widespread weeds in
Klamath County, it infests crops, pastures, forests,
rangelands, roadways, and lawns. Very hard to
control or eradicate, Canada thistle is a major pest.
9
© 2005 Michael Calonje

Sunflower Family (Asteraceae)
Scotch thistle
Onopordum acanthium L.
60
© 2005 Michael Calonje

Description: Biennial up to 12 feet tall. Stems are
broad, winged, and spiny. Leaves are large, hairy
with spines, and alternate. Basal leaves may be 2 feet
long and 1 foot wide. Flower heads are numerous, 1
to 2 inch diameter, and violet to red. Fruits are 3/16
inch long and tipped with slender bristles.
Habitat: Native to Europe and eastern Asia.
Aggressive plants are found in waste areas and
roadsides. Forms dense stands.
Economics: Long viability of seeds and dense stands
combine to make this plant a major pest. It may
form stands so dense that wildlife, livestock, and
recreationists cannot pass through it.
Picture from Weeds of the West - used with permission.
6
© 2005 Michael Calonje

Sunflower Family (Asteraceae)
Tansy ragwort
Senecio jacobaea L.
62
© www.nwcb.wa.gov

Description: Biennial or short-lived perennial
standing from 1 to 6 feet tall. Plants have large
taproot. Stems are slightly branched or solitary.
Leaves are 2 to 8 inches long, alternate, and 2 to 3
times pinnately lobed. Flower heads are numerous,
bright yellow, and clustered at top of stem. Flowers
from July to September. Fruits are minutely hairy
from disk flowers and smooth from ray flowers.
Habitat: Native to Europe. Plants like pasture and
rangelands.
Economics: A poisonous plant that is toxic to cattle
thus resulting in economic losses to producers. All
parts of this plant are poisonous both in the vegetative
and dried stages.
Copyright © Province of British Columbia. All rights reserved. Reprinted with
permission of the Province of British Columbia.
63

Sunflower Family (Asteraceae)
Spiny cocklebur
Xanthium spinosum L.
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© 2005 Michael Calonje

Description: Annual with spreading or erect stems
up to two feet long.believes have numerous white
hairs, white veins, and are deeply divided. Male
flowers are located on top of the plant with female
flowers below. Flowers are tightly clustered. Spiny
fruit resembles bur with hooked bristles.
Habitat: Native to Europe. Plants occur in dry areas
like barnyards and roadways.
Economics: A nuisance to recreationists, this plant is
also toxic to grazing animals.
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© 2005 Michael Calonje

Glossary
alternate - singly along a stem; one leaf or bud per
node.
annual - plant which germinates, flowers, sets seed,
and dies in one year.
apex - tip.
basal - positioned at or arising from the base.
biennial - plant which germinates, flowers, sets seed,
dies in two years.
bract - small leaf-like structure at base of flower.
capsule - dry fruit which opens to release seeds.
entire - leaf edges are not toothed or serrated.
glabrous - smooth; without hairs.
globular - spherical
lanceolate - lance-shaped; longer than wide, with
widest point below middle.
lateral - on the side.
leaflet - one small blade of a compound leaf.
monoculture - area where only one type of plant
grows.
node - joint on a stem where stems and leaves
originate.
nutlet - small nut, maybe one section of larger fruit.
oblong - longer than wide.
opposite - arranged on the same node on opposite
sides of the stem.
parasitic - obtains food or water from host plant.
perennial - plant which germinates, flowers, sets
seed, and dies over many years.
pinnate - compound leaf with leaflets arranged on
opposite sides of elongated axis.
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pistil - female reproductive part of flower.
rosette - compact cluster of leaves arranged in basal
circle, usually at ground level.
silicle - dry fruit usually twice as long as wide with
two sections that release seeds when ripe.
spur - hollow, slender appendage of petal or sepal.
stamen - male reproductive part of flower.
terminal - at the tip or apex.
umbel - flat or rounded flower cluster in which stalks
radiate from same point, like an umbrella.
whorled - parts arranged in whorls, like many leaves
from one node.
Notes:
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References
Weed Handbook Series 1-55, Wyoming Weed and
Pest Council.
Weeds of the West. The Western Society of Weed
Science in Cooperation with the Western United
States Land Grant Universities Cooperative
Extension Service. Revised 1992.
The Grower’s Weed identification Handbook,
Publication 4030, Cooperative Extension, University
of California.
The Jepson Manual: Higher Plants of California,
University of California Press. 1993.
Plant Identification Terminology: An Illustrated
Glossary, J. Harris and M. Harris. Spring Lake
Publishing, 1994.
Biology and Management of Noxious Rangeland
Weeds, Oregon State University Press, 1999.
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Weed Control References
Klamath County Extension Office, Oregon State
University, (541) 883-7131
Klamath County Weed Department,
(541) 883-4696
Oregon Department of Agriculture, Noxious Weed
Control Division, (541) 850-9550
PNW Weed Control Handbook
Klamath-Lake Forest Health Partnership, (541) 883-
5681
Weed Web Sites
Aphis Web-Noxious Weeds Home Page
http://aphis.usda.gov
Oregon Department of Agriculture
http://www.oda.state.or.us
University of California Davis
Weed Research Center
http://wric.ucdavis.edu
Western society of Weed Science
http://www.wsweedscience.org
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Noxious Weed Survey
Surveyor: Date:
Weed Species:
Area of infestation:
Number of plants:
Plant density: Lifestage:
Location:
Township: Range: Section:
Habitat description:
Eradication action:
Other comments:
70

Noxious Weed Survey
Surveyor: Date:
Weed Species:
Area of infestation:
Number of plants:
Plant density: Lifestage:
Location:
Township: Range: Section:
Habitat description:
Eradication action:
Other comments:
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Rabe Consulting