Download Southwest Oregon Invasive Species Network Invasive Species

Southwest Oregon
Invasive Species Network
What is Early Detection & Rapid Response?
Early Detection and Rapid Response (EDRR) is an approach to
invasive species management that focuses on surveying and
monitoring areas to find infestations at their earliest stages of
invasion. Monitoring can be either passive (during normal work or
recreation), or active (by searching a particular area repeatedly for
invasive species).
Once found, control of a new invader is begun rapidly to prevent its
establishment and spread. After prevention, EDRR is the most
successful, cost effective, and least damaging means of invasive
species control.
Early Detection Identification Guide
Resources
Noxious Weeds in the State of Oregon:
http://www.oregon.gov/ODA/PLANT/WEEDS
Aquatic Invasive Species Information:
http://egov.oregon.gov/OSMB/Clean/ANS.shtml
Neighboring states/provinces:
http://www.nwcb.wa.gov/index.htm
http://www.agf.gov.bc.ca/cropprot/weeds.htm
http://www.cal-ipc.org
http://idahoweedawareness.net/index.html
Early Detection Report Form
Date:__________ Observer:__________________
Location:__________________________________
__________________________________________
Plant Species:_______________________________
Patch Size: Length_________ ft. Width_________ft.
% cover_____________# of plants______________
Photos and control information:
http://www.invasive.org
Type of site (riparian, road, forest, trail, etc):
General invasive species information and resources:
http://emswcd.org/weeds
http://www.opb.org/programs/invasives
http://www.kingcounty.gov/environment/animalsandplants/
noxious-weeds.aspx
http://www.invasivespeciesoforegon.com
http://www.westerninvasivesnetwork.org
http://plants.usda.gov
Notes (landowner, location, physical description,
Reporting Invasives:
http://www.oregoninvasiveshotline.org
__________________________________________
directions, etc.)
__________________________________________
__________________________________________
__________________________________________
__________________________________________
How to Report Invasive Species
If you suspect that you have found any of the species included in
this ID guide in Jackson County, please record the following
information so that we can follow up on your report.
1. Take a picture: Include something to show scale (a ruler or a
common object like a quarter) and close-ups of distinctive features.
Take your time to make sure the photo is in focus.
2. Collect a written description: Make a note of it’s color, shape and
size and any other distinctive features.
3. Collect location information: GPS coordinates are the best,
written directions to the site work too. Nearby landmarks such as
closest address, intersection or mile marker, or how far past a trail
or bridge crossing, are very helpful.
4. Record size of infestation: How many feet wide and how many
feet long is the infestation? Or you may estimate the number of
individuals at the site.
5. Visit www.oregoninvasiveshotline.org: Click on the ‘Report Now’
button. Fill out the form, making sure you provide all of the
information listed above. Use the Google map function in “hybrid”
mode to zoom down to approximately mark your invader’s location.
Make sure to add your images of the invader.
6. Report by phone: If you do not have Internet access, you can call
your report in to The Nature Conservancy Southwest Oregon Field
Office at (541) 770-7933 or call 1-866-INVADER.
Sketch Map
Southwest Oregon
Invasive Species Network
The Southwest Oregon Invasive Species Network (SWORISN) is a
partnership between volunteers, non-profits, and government
agencies to promote Early Detection and Rapid Response (EDRR) to
new invasive species in SW Oregon (Jackson and Josephine
Counties). Volunteers and agency, industry, or non-profit staff look
for and report new, high priority invasive species in the region.
Reports are then investigated, mapped and prioritized for control
by various partnering groups and/or agencies and private land
owners.
This EDRR invasive species identification guide was developed to aid
in identifying, detecting, and reporting the invaders that have been
given priority for early detection and rapid response in SW Oregon.
It contains background information, identification tools, and
protocols for documenting and reporting. Thank you in advance for
your commitment to keeping invasive species out of our region.
SWORISN can provide trainings to individuals, groups, and
organizations so they can help in the effort to prevent new invasive
species from establishing in the region. We need your help! To
become a volunteer, contact The Nature Conservancy Southwest
Oregon Field Office at (541) 770-7933.
Acknowledgements
(Use to describe location if more detail is needed)
This guide was compiled by Bruce Campbell (TNC volunteer),
Robert Emanuel (Oregon Sea Grant), Tania Siemens (TNC and
Oregon Sea Grant), Molly Sullivan (TNC), and Lucy Whitridge
(AmeriCorp volunteer at North Mountain Park, Ashland). Some
material was adapted from the “Weed Watchers EDRR ID
Guide for Multnomah County & Sandy River Basin” (2009). The
cover photo of milk thistle was taken by Tania Siemens.
Support for production of this guide was supplied by Oregon
Watershed Enhancement Board, The Nature Conservancy, and
Oregon Sea Grant Extension.
Anyone requesting use of the materials herein should send an
inquiry to Tania Siemens at: [email protected].
Please use the information on this card to
submit your report to
http://oregoninvasiveshotline.org
Jackson County CWMA
Cooperative WeeD
Management Area
Photo © Tania Siemens/TNC
Yellowtuft
Cutleaf teasel
Photo courtesy Illinois Wildflowers
Photo courtsey Pittsburg State
Dyers woad
Photo © Harri Arkkia
Yellow floating heart
© Shu Suehiro
© 2001 CDFA
Flowers in bloom (Spring)
Photo Trinity Co. Res. Con. Dist.
Fruits in early summer
Fruits in late summer
Photo © Steve Dewey
Photo U. of Idaho
Photo U of Idaho
© Glenn Miller, ODA
Yellowtuft
Cutleaf teasel
Alyssum murale
Dipsacus laciniatus
General: Upright growing herbaceous annual introduced from
southern Europe as an ornamental, especially in rock gardens.
Grayish-green foliage in spring, blooming by late May.
General: Biennial; first year’s growth a rosette. Flowers July to
September. Grows up to seven ft. tall. Stems tall and prickly. Used
in flower arrangements.
Leaves: Covered with fine white hairs giving plant grayish-green
tint.
Leaves: Rosette leaves relatively large, oblong , and incised (deeply
cut). Mature leaves opposite, large, oblong and prickly.
Flowers: Yellow flowers are borne in clusters at the top of slender
stalks that grow from 10 to 24 in. tall. Individual flowers are less
than ¼ in. wide, but the flat-topped flower clusters may be several
inches wide.
Flowers: Individual flowers are small with four white petals in dense
egg-shaped heads with many slender bracts that become stiffhooked prickles when ripe. First flowers open in a “belt” around the
center of the spike, new flowers open toward the top and bottom
of the spike, giving two bands of flowers. Numerous narrow
involucral bracts (modified leaves) arise at the base of the flower
heads and extend past the spikes becoming stiff and prickly when
dry.
Fruit: Flattened oval seed pods are 5–8 mm long, have star-like
hairs, and are held close to the stem. Pods are chambered, with
each chamber containing 3–7 seeds. Seeds, 2–3 mm long, are
aligned in rows in the chambers. Plants produce many seeds.
Notes: Thrives in well drained, rocky , serpentine soils. Can take up
metals like nickel and store them in its leaves, flowers and stems,
thus providing an adaptation for growth on soils that otherwise
might be toxic.
Impacts: Poses serious risk to native plants and grazing livestock.
Can crowd out native plants and is toxic to livestock.
Fruit: Simple dry fruit, 1/8 in. long, crowned by calyx (sepals), 1
seed, hairy, grayish brown.
Notes: Similar to common teasel (Dipsacus fullonum), except
flowers white rather than lilac, and the leaves are incised.. Both
rosettes and mature plants can be removed by digging. Mowing or
cutting is only effective over a period of years if the plants are cut at
ground level before seed forming. Herbicides should be applied to
rosettes in the early spring or late fall.
Impacts: Invasive in grasslands, savannas and waste areas.
Yellow floating heart
Dyer's woad
Nymphoides peltata
Isatis tinctoria
General: Aquatic perennial. Waterlily-like floating leaves attached
to long stems rooted to the bottom in water depths of 2-13 feet.
Introduced to the United States as an ornamental.
Leaves: Heart-shaped leaves are 1 to 4 inches long, green with
purplish undersides and wavy along the edges. Leaves attached to
long stalks that arise from creeping underwater rhizomes.
Flowers: Showy yellow flowers have five petals and are about an
inch in diameter. The petals are arranged like spokes on a wheel
and are fringed along the margins. Flowers borne on upright stalks,
a few inches above the water, with two to five flowers on each
stalk.
Fruit: One inch long containing numerous seeds. Seeds are flat, oval
and about 15 inches long with hairy edges.
Notes: Prefers slow moving rivers, lakes, reservoirs, ponds and
swamps. Can also grow on damp mud. Grows in water from 1 1/2 to
10-15 ft. deep, where it dominates with a thick mat of floating
leaves. Control is difficult and eradication may be unrealistic.
Bottom barriers can be used in small areas, to prevent growth.
Remove all plant parts if cut.
Impacts: Forms dense mats, which interfere with recreation, water
movement, water quality, and native plants and animals.
General: An upright, branching, bi-annual herb 1-3 ft. tall, with a 3-5
ft. long taproot. First year as a rosette the following year multiple
stems can arise from a single base.
Leaves: Basal rosette produces stalked, bluish-green leaves covered
with a fine hair. Rosette leaves range from 1 ½ to 7 in. long, and are
succulent. All leaves have cream colored mid-rib from tip to base.
Leaves along second year plant stem are lance shaped, alternate
and not stalked, clasping stem with short basal lobes.
Flowers: Cross-shaped small yellow flowers with 4 sepals, 4 petals
and 6 stamens. Two outer stamens shorter than 4 inner
stamens. Petals about 1/8 in. long and wide. Petals twice as long as
sepals. Flowers in clusters at branch tips.
Fruit: Flattened seed pod, 3/8 in. long, ¼ in. wide, winged, slightly
pear shaped, hanging from a small stalk. Immature pod hairless and
green, turning black or dark purplish-brown at maturity. Pod
produces 1 brownish-yellow, cylindrical seed.
Notes: Prefers light sandy and gravelly soils. Control with herbicide
before plant bolts. Cultivation twice a year, once in spring and again
in late fall effective. Mowing or hand pulling after plant bolts and
before seed production also effective.
Impacts: Crowds out native vegetation and reduces yields of range
lands and hay.
Tansy ragwort
Photo courtesy Arizona Cooperative Extension
Photo courtesy UIdaho
Photo © Kurt Stueber
Courtesy Dan Sharratt, ODA
Photo courtesy BC Ministry Ag.
Spanish broom
Garlic mustard
© Tania Siemens/TNC
Photo Christin Hanrahane
Photo courtesy Rhydwyn
Invasives.org
Photo courtesy Whenimbadimbetter
Yellow starthistle
Tansy ragwort
Centaurea solstitialis
Senecio jacobaea
**Please do not report from Jackson County.**
General: Aggressive and adaptable annual that poses a great threat
to native plant communities and wildlife. Grows to a height of 2 to 5
ft.. Stem are erect and rigid, bearing many branches and covered
with white cottony hair.
Leaves: Foliage is grey to bluish-green, spring rosette leaves deeply
lobed appearing ruffled along edge. Mature plant leaves nearest to
the soil deeply lobed, upper stem leaves almost linear or narrowly
oblong. Leaf bases extend down stems giving them a winged
appearance.
Flowers: Blooms July through September. Bright yellow thistle –like
flower heads located singly at the ends of branches, and are armed
with thorns up to ¾ in. long.
Fruit: Single plant can produce over 150,000 seeds. Glabrous, 4 mm
long, plumed and unplumbed seeds produced.
Notes: Seeds germinate in fall and young plants exists as basal
rosettes through the winter and bolt in spring. Biocontrol,
mechanical, cultural and chemical control methods known to
reduce populations.
Impacts: Reduces land value and displaces native plants, decreasing
wildlife forage and native plant and animal diversity. Provides poor
livestock forage and causes a nervous disorder in horses.
General: Aggressive biennial that germinates in the fall and exists
its first year as a basal rosette, bolting in year two.
Produces and large woody rootstock.
Leaves: Rosette has deeply indented, blunt-toothed lobes. Mature
plant with alternate, sessile stem leaves . Basal leaves hairless to
lightly covered with whitish cottony hairs. Especially on underside.
Flowers: Yellow daisy-like with 13 petals. Flower inflorescences
comprised of 20-60 flowers in flat topped clusters.
Fruit: Seeds mature in August and spread by wind. Single plant
produces up o 200,000 seeds that can remain viable in soil for up to
15 years.
Notes: Prefers full sun and open sites with moderately moist soils.
Small infestations controlled by hand pulling before flowers
produce seeds. Large infestations better controlled by manual and
chemical means. Mowing ineffective and may cause re-sprouting.
Biological controls available.
Impacts: All parts of plant toxic to cattle and horses by causing
irreversible liver damage. Estimated to have caused more than $4
million in livestock loses in 1970. Reduces quality of pastures and
hay.
Spanish broom
Garlic mustard
Spartium junceum
Alliaria petiolata
General: Bright green, perennial, drought tolerant evergreen shrub
reaching up to 10 ft. tall. Closely related to Scotch broom.
Introduced as an ornamental. Considered a potential fire hazard.
Leaves: Primarily leafless. Few existing leaves appear from Feb. to
early June. Leaves are simple, less than 1 in. long, and sparse.
Flowers: Begins blooming in late May and continues through first
frost. One inch long, bright yellow, fragrant pea-flowers clustered at
stem tips.
Fruit: Spreads by seeds or stump sprouts. 5,000-10,000 seeds
produced per plant. Seeds which can remain viable for up to 25
years, fall near plant and are moved by erosion, rain, and animal
activity.
Notes: Grows in disturbed areas. Prefers sunny dry areas with rocky
or poor soils. Can be controlled by mechanical and chemical
methods. Hand pulling or digging is effective for small infestations if
entire root is removed. Herbicides are also effective.
Impacts: Replaces native plants and habitats reducing plant and
habitat diversity. Poisonous to livestock and humans.
General: A herbaceous biennial. First year rosettes of 3-4 dark
leaves. Second-year plants produce flowering stems 2-3.5 ft.
tall. Crushed leaves smell like garlic.
Leaves: First year rosettes have green, kidney-shaped, scallopedged leaves. Stem leaves of second-year plants alternate,
heart-shaped and coarsely toothed.
Flowers: Flowers 1/4 in. wide with 4 white petals forming a
cross. In button-like clusters.
Fruit: Seedpods are skinny, 1-2.5 in., turning tan by
midsummer. They split along seams to release small black
seeds.
Notes: Invades forests, roadsides, streamsides, trails, and
agriculture lands. Garlic mustard control is a multi-year project
because the seed bank can remain viable for years. Plants are
easily pulled when soils are moist. If flowering, plants must be
bagged as seeds can continue to ripen after plant is pulled.
Cutting plants a few inches above ground just after flower
stalks have elongated can be effective in preventing seed
production. Herbicides can be used to control larger
infestations.
Impacts: Displaces native forest understory species, reducing
diversity and forage availability. Adversely affects several
native butterfly species.
Dalmation toadflax
Flower. USDA APHIS
Seedling. John D. Byrd
Photo: Mel Harte
Russian thistle
Puncturevine
Image © Mandy Tu/TNC
False brome
Spikelets on
long stalks
False brome
Native Bromus vulgaris
© John M. Randall/TNC
Photos Andrea Thorpe
Dalmation toadflax
Russian thistle
Linaria dalmatica
Salsola kali
General: A perennial herb. Mature dalmation toadflax plants grow to
2.5 to 5 ft. tall. Strong upright floral stems. The tap root may penetrate
one meter into the soil. Reproduces by seed and vegetative propagation.
Leaves: Alternate, heart shaped, waxy leaves.
Flowers: Bright yellow flowers that resemble snapdragon. Flowering
occurs from May-August .
Fruit: Seeds mature from July- September.
Notes: Occurs on open sites with sandy or gravelly soil but can also
invade coniferous forests, oak, sagebrush, and riparian
communities. Successful control can be obtained by pulling, or killing the plants
with herbicide, before toadflax seed
production begins. It can be
very tough to control by pulling because of creeping perennial root
system. Ideally, it will be detected early in the season (May and June)
when it is easier to pull and before seed set. Planting competitive native perennial grasses can help prevent reestablishment.
Impacts: Once established, toadflax suppresses other
vegetation
mainly by intense competition for limited soil water. Using adventitious buds from creeping root systems, toadflax forms colonies that
can push out native grasses and other perennials.
False brome
Brachypodium sylvaticum
General: This perennial grass forms short, squatty bunches. Its
hollow stems are 1/4-1/3 in. wide and bear soft hairs at the nodes.
Reproduces by seed and re-sprouts from stem or root fragments
when cut.
Leaves: Broad, flat, and bright green and remain so through fall and
part of winter. The margins and lower stems of the leaves are hairy,
and open-sheathed at the base. The ligules are membranous.
Flowers: The flowers are located on short, pale-green spikelets that
noticeably droop and have short stalks.
Fruit: Appears that seed banks do not remain in the soil for longer
than one year.
Notes: Grows primarily in coniferous forest understory, but is also
habitating riparian forests, forest edges, and upland
prairies. Please report but do not try to pull as it is easily confused
with native grasses. Control methods are not well studied, but it
appears that herbicide use is most effective. The native look-alike is
Columbia brome, Bromus vulgaris, which has spikelets that are
stalked.
Impacts: Displaces native understory plants, suppresses forest
regeneration, degrades wildlife habitat and increases fire risk.
*This plant is already locally abundant in SW Oregon.*
*Please only report from natural areas.*
General: Russian thistle is an annual tap-rooted forb that grows 1-3
ft. tall. Seedlings look very similar to pine tree seedlings. Erect, spiny
and profusely branched. The stems of young plants have red or purple stripes. Reproduces by seed.
Leaves: The green leaves are alternate, threadlike, stalkless, cylindrical or awl-shaped with pointed tips.
Flowers: Flowers are small, greenish, and lack petals. Papery, spinetipped bracts are at the base of each flower. It typically blooms from
July through October.
Fruit: Produces seed until temperature drops below 25° F.
Notes: It commonly grows in disturbed areas, river bottoms, streams,
lakes, coastal dunes and sandy beaches. Russian thistle can be handpulled so long as you are sure of its identification. Take care not to
spread seeds. It can be prevented by planting desirable competing
plants
Impacts: Russian thistle can dominate areas that experience drought
conditions or have been cleared of competing
vegetation. It competes with native species, blocks stream channels and roadways, and
can become a fire hazard.
Puncturevine
Tribulus terrestris
*This plant is already locally abundant in SW Oregon.*
*Please only report from natural areas.*
General: A ground covering summer annual herb that grows from a
simple woody taproot. Many green to reddish-brown stems up to 6 ft
long. Stems have many branches that arise from the crown to produce a dense mat. Reproduces entirely by seed.
Leaves: Opposite with short, oblong petioles divided into 4-8 pinnate
leaflets and are covered in silky to bristly silver hairs.
Flowers: Small, yellow, five petaled flowers are borne on short stalks
at the leaf nodes. Flowers bloom July-October.
Fruit: The fruit is a woody burr with sharp, rigid spines that are strong
enough to puncture bike tires or shoe soles. Seeds are produced in
late summer through autumn.
Notes: Commonly found in disturbed sites and agricultural areas.
Small populations can be hoed or pulled above the tap root before or
during flowering. If the seeds have developed, remove material from
the site. Two biocontrol agents, the seed and stem weevil, may be
successful.
Impacts: Already a nuisance in many Oregon counties, it continues
to spread into open areas. Its success is due to its ability to thrive in
hot and dry conditions where most other plants cannot. Burrs are a
hazard to humans and animals.
Leafy spurge
White top
A young shoot.
Image by William M. Ciesla,
Image courtesy of
Dan Sharratt, ODA
Photo © Barry A. Rice/TNC
Image courtesy of
Dan Sharratt,, ODA
Image © John M. Randall/TNC
Image
courtesy of Lesley
Rush skeletonweed
Knapweeds
Meadow Knapweed
Image courtesy of British Columbia
Ministry of Forests
Photo Cindy Roche
Image courtesy WSSA
Spotted Knapweed
Photo by Eric Coombs, ODA
Basal rosettes. © John M. Randall/The Nature Conservancy
Squarrose Knapweed
Photo by Dan Sharrett ODA
Diffuse Knapweed
Image WSSA
White top (Hoary cress)
Leafy spurge
Cardaria draba
Euphorbia escula
General: A long-lived rhizomatous perennial about 2 ft tall. It reproduces by seeds which usually germinate in the fall and remain a rosette until the following spring. They also spread by lateral roots.
General: An upright, branching, perennial herb 2-3 ft tall. Seedlings
are deep red-purple. It is one of the first plants to emerge in spring.
The first seedling shoot produced usually dies and is replaced by its
adventitious shoot that will mature into the flowering shoot.
Leaves: Basal leaves are blue-green and lance shaped; the upper
leaves have two lobes clasping the stem. Leaves are covered with fine
white hairs that give the plant a grayish green appearance.
Flowers: White flowers are in clusters at the top of slender stalks that
grow 10-24 in. tall. Individual flowers are less than ¼ in. wide with 4
petals and 6 stamens. Blooms in early May.
Fruit: A ½ in. long heart-shaped seedpod, which is reddish brown and
tipped with a small beak. Seeds mature in summer.
Notes: Found in many unshaded disturbed areas. Only pull early in
the spring when plants are seedlings. Get the lateral and vertical
roots or new plants will develop. Mechanical control in fall-early
spring is appropriate for small seedling stands. Chemical control is
difficult because desirable broad-leaved plants, both native and crop
species, are often present.
Impacts: The early season growth of this plant reduces soil moisture
and nutrients available to native species.
Spotted knapweed—Centaurea maculosa
Russian knapweed—Acroptilon repens
Meadow knapweed—Centaurea pratensis
Squarrose knapweed—Centaurea virgata
General: Biennial or short-lived perennials (except Russian knapweed
is a rhizomatous perennial). Grows 3 ft tall, and is multi-stemmed,
with the majority of its slender stems branching from the upper half.
Reproduces by seed.
Leaves: Forms a basal rosette of leaves in the first year and flowers in
subsequent years. Leaves are 8 in. long, borne on short stalks, and
may be lobed
Flowers: Flowers are urn-shaped, and pink, purple, or white. Bracts
are fringed at the margins. Blooms July-August.
Fruit: Each plant produces 400 or more seeds per flower stalk.
Notes: Commonly found on pastureland or any other open ground.
Squarrose not known in Southwest Oregon but is nearby in Yreka.
Spotted has limited distribution. Seed longevity makes controlling it
difficult. Successful methods include biological, mechanical, grazing
and herbicide.
Impacts: They have more negative impacts on ecosystems than any
weed in the West. In Oregon, knapweeds have cost us nearly $54
million. They out-compete native plants, degrade soil water resources through erosion, runoff, and stream sedimentation.
Leaves: Alternate narrow leaves, somewhat frosted and slightly wavy
along the margins.
Flowers: Very small and borne in greenish-yellow structures surrounded by yellow distinctive heart-shaped bracts.
Fruit: Fruits ripen and seeds are dispersed in July. Seeds are dispersed by the explosive seed capsule and along streams.
Notes: Invades disturbed areas. Pulling can stimulate additional
growth. Prescribed burning with herbicide application can provide
control. Treatments are necessary over a 5-10 yr. period. Caution:
Contains an acrid latex sap which may cause a rash when sap on the
skin is exposed to sunlight, and can cause permanent blindness if
rubbed on eyes.
Impacts: Unless detected early, it is nearly impossible to control due
to deep and extensive root systems. It is tolerant of a range of habitats on rich damp soils or nutrient poor, dry soils.
Rush skeletonweed
Chondrilla juncea
General: A perennial 1-4 ft. tall. Juvenile plants overwinter as a rosette of basal leaves. Mature plants are dark green, nearly leafless,
with many branches. It has coarse downwardly-bent hairs that cover
the lower 4-6 in. of the stem. When cut it exudes a white latex sap.
Reproduces by seed and vegetative
Leaves: Hairless basal leaves are 2-5 in. long and widen towards the
tip. Lateral lobes on the leaves of the basal rosette point backwards
toward the base.
Flowers: Yellow flower heads are ¾ in. in diameter growing
along the stem in the leaf axil or at the branch tips. Flower heads
grow individually or in clusters of 2-5.
Fruit: Similar to dandelions, seeds have a pappus of numerous white
capillary bristles that are carried by the wind.
Notes: Found in light, dry soil typically on rangelands and roadsides.
Control before summer seed set. Spot it in fall-winter as a basal rosette. There are 4 approved biocontrol agents in Oregon. Herbicides/
mechanical methods are not very effective control measures.
Impacts: Rush skeletonweed is an aggressive plant in both rangeland
and cropland, threatening primarily cereal grain and potato production.
Woolly distaff thistle
Knotweeds
Woolly distaff thistle
rosette
Giant Knotweed
Image Ken French
Photo©JonathaSol/TNC
Japanese Knotweed
Scotch thistle
Scotch thistle stem
University of Cincinnati -Clermont College
weedy-connection.com
Photo©Jennifer Forman
Jenn Grieser, New York City Department of Environmental Protection,
Bugwood.org
Washington Noxious Weed Board
Milk thistle
WA Noxious Weed Board
Musk thistle
Photos © Tania Siemens/TNC
Image James Miller
Image Weed Science Society of America
Scotch thistle
Giant knotweed
Onopordum acanthium
Polygonum sachalinense
Woolly distaff thistle
Japanese knotweed
Carthamus lanatus
Polygonum cuspidatum
General: Woolly distaff is an annual with round stems. Scotch thistle
is a biennial with vertical rows of spiny, ribbon-like leaf material on
the stems. Reproduction is by seed.
Leaves: Lance-shaped and spiny. Rosettes grow in spring (Scotch
thistle found as a rosette all of the growing season).
Flowers: Woolly distaff has yellow flowers on solitary heads with leaf
-like rigid spiny bracts around base. Scotch thistle has dark pink,
globe-shaped flower heads, 2 in long, with long needle-like bracts at
the base. Flowers bloom in summer.
Fruit: Seeds are dispersed locally by wind; humans, water, livestock,
and wildlife are involved in long-distance dispersal.
General: Giant Knotweed is an herbaceous perennial, strongly
rhizomatous, growing over 12 ft. tall. Hollow stems are jointed
and swollen at the nodes, resembling bamboo.
Japanese Knotweed is similar to giant knotweed except has
smaller leaves and reaches a height of only 4 to 8 ft.
Leaves: Heart-shaped and alternate on the stem. Giant knotweed leaves are much larger, exceeding one ft. in length and 8
in. wide - twice the size of Japanese knotweed.
Flowers: Flowers are whitish and borne in open, drooping panicles.
Notes: Woolly distaff infests drier sites. Scotch thistle inhabits moist
sites or drainages in dry locations. Be certain of the identification
before pulling thistles and do not to disperse seeds. Control at the
rosette stage by cutting off the rosette just below ground level with a
sharp shovel. Mowing of woolly distaff can be effective if done just
before bloom. Herbicides are also effective if applied to rosettes or
early bolting plants .
Fruit: Fruits are shiny black, triangular, about 1/6 in. long.
Impacts: Thistles crowd out other vegetation, livestock and recreational access.
Impacts: Dense stands exclude other plant species leading to
very limited biological diversity in infested sites.
Notes: Both species are found along stream banks, moist waste
places, neglected gardens, roadsides, and railroad right-of-ways.
Extensive rhizomes make control difficult. Limited success with
herbicides. Mechanical removal not effective due to the viability
of rhizome fragments
Musk thistle
Milk thistle
Carduus nutans
Silybum marianum
General: A biennial with bolting plants that are multi-branched and
can reach 6 ft. Reproduction is by seed.
General: Biennial or winter annual; blooms from April to July.
Grows two to six foot tall. Reproduction is by seed.
Leaves: Rosettes grow in spring. Leaves have a smooth waxy surface
and a yellowish to white spine at the tip.
Leaves: Leaves broad, clasp stem, have spiny margins and have white
marbling along veins.
Flowers: Large, showy red-purple, disk-shaped flowers that bloom in
the summer. Flower heads will droop from the stem when mature.
Flowers: Flower heads reddish-purple and have leathery spine-tipped
bracts.
Fruit: Seeds are dispersed locally by wind; humans, water, livestock,
and wildlife are involved in long-distance dispersal.
Fruit: Seeds are dispersed locally by wind; humans, water, livestock,
and wildlife are involved in long-distance dispersal.
Notes: It invades open natural areas such as meadows, prairies, and
grassy balds. Look for rosettes in July and flowers July through August. Control at the rosette stage by cutting off the rosette just below
ground level with a sharp shovel. Herbicides are also effective if applied to rosettes or early bolting plants. Be careful not to spread
seeds when pulling thistles. Musk thistle is not known in southwest
Oregon, but heavy infestations are reported from Klamath County.
Notes: It infests roadsides, waste and disturbed areas, grazing lands
and often occurs in association with Italian and slender-flowered
thistles. Milk thistle seed is valued as an herbal medicine. Small infestations can be effectively dug up. It is abundant in Western Oregon,
but Jackson County remains relatively free of milk thistle.
Impacts: Thistles crowd out other vegetation, livestock and recreational access.
Impacts: Once established, it forms dense clumps which exclude
livestock and crowd out more desirable forage species. It has the
potential to invade extensive acres of pasture land.