Tag Archives | weed profile

Welted thistle (Carduus crispus)

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Common names:

Welted thistle, curly plumeless thistle

Scientific Name:

Carduus crispus

Description:

A large growing thistle Stems are openly branching, hairy with curled hairs to nearly smooth. Stems have spiny wings to 1.5 cm wide, and sport wing spines 3 mm long. The leaves have winged petioles at their base. Leaf blades are 10–20 cm long with spiny-toothed margins. Flower heads are borne singly or in groups of 2–5, 15–18 mm wide. Flower peduncles are spiny-winged to near apex or throughout, to 4 cm wide. Flower corollas can be either purple or white. Flower parts are both male and female.  Insect pollination is required. Reproduction is entirely by seed.  Carduus crispus closely resembles the more common C. acanthoides (plumeless thistle).

Life cycle:

Annual to biennual

Height of mature plants

1- 5 feet

Flower color:

Purple or pink to white

Bloom time:

Flowering occurs July through September.

Look-a-likes:

Similar to other thistles.  Very closely resembles the more common plumeless thistle (Carduus acanthoides)

Habitat:

irrigation ditches, field margins, waste ground, pastures, and roadsides

Impacts:

Likely contaminant in grass and alfalfa hay, reducing its quality and marketability. Welted thistle seeds may also be a contaminant in alfalfa, grain, or grass seed. Infested grasslands and pastures may see a reduction in productivity when thistle densities reach high levels. This spiny thistle would act as a deterrent to most grazing.

Noxious Weed Listing:

Origin:

Native to Europe and Asia.  The first record of welted thistle occurred in the Eastern U.S. in 1974. In 2016, a new western infestation was detected in Wallowa County, Oregon.

Present in Clackamas County:

Not known to occur

Links:

Oregon Noxious Weed Risk Assessment

Plants Database Profile: Carduus crispus

CABI Invasive Species Compendium Datasheet

 

Yellow Nutsedge (Cyperus esculentus)

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Common names:

Yellow nutsedge, nut grass

Scientific Name:

Cyperus esculentus

Description:

Yellow nutsedge is a perennial sedge in the Cyperaceae (sedge) family. It is considered to be one of the world’s worst weeds and it occurs on every continent (except Antarctica). Like many sedges, yellow nutsedge has a triangular cross section. Its leaves are shiny and yellowish-green with a prominent mid vein and a pointed tip. The flower is a golden brown cluster at the end of the stems. It spreads from a network of underground rhizomes, tubers and bulbs.

Life cycle:

Perennial

Height of mature plants

12 – 32 inches

Flower color:

Golden brown

Bloom time:

July – August

Look-a-likes:

Yellow nutsedge may be confused with other sedges that have triangular stems, especially tall flatsedge. However, yellow nutsedge has a loose, open flower head, while tall nutsedge has more of a dense, spherical cluster.

Habitat:

Yellow nutsedge grows best in moist areas, and thus it can be found in irrigated agricultural areas, ditches, and along the shores of lakes rivers, streams, and marshes.

Impacts:

Yellow nutsedge is considered to be one of the world worst weeds. It can form dense stands, reducing crop yields and outcompeting native plants for resources. It can be difficult to control because of its underground system of rhizomes, tubers, and bulbs. If even one tuber is left behind, the plant can quickly regenerate. The tubers can also stay viable in the soil for 3 to 4 years. Some research suggests it produces a chemical that is harmful to crops.

Old Man’s Beard (Clematis vitalba)

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Common names:

Old man’s beard, traveler’s joy

Scientific Name:

Clematis vitalba

Description:

Old man’s beard is a deciduous, perennial climbing vine in the Ranunculaceae (buttercup) family. It was introduced as an ornamental plant, but it has spread rapidly across western Oregon, especially in the north end of the Willamette Valley. This plant is also known as “traveler’s joy”, as its rapidly growing vines can grow 10 feet a year, and can reach 90 feet in length. The greenish-white flowers grow in clusters of 3 to 22. The leaves are opposite and compound with 5 leaflets (sometimes 3). The seed heads are feathery and white, giving the plant its name. New stems are deeply ridged, while the older bark is gray and stringy. It produces large quantities of seeds and can also spread by stem fragmentation.

Life cycle:

Perennial

Height of mature plants

Up to 90 feet in length

Flower color:

greenish-white to creamy-white

Bloom time:

Summer

Look-a-likes:

Old man’s beard looks similar to native varieties of clematis. One native, C. ligusticifolia only grows to about 20 feet in length and has 5-7 leaflets, while old man’s beard grows up to 90 feet in length and has 5 leaflets (sometimes 3). The other native look alikes, C. lasiantha and C. pauciflora, flower from January to June, while old man’s beard flowers from June to September.  Old man’s beard is also sometimes confused with ivy. However, ivy is evergreen and does not have compound leaves like old man’s beard.

Habitat:

Old man’s beard typically grows in sunny disturbed areas, however, it can also grow in part sun to full shade. This plant can be found in forest margins and gaps, riparian areas, fence lines, and roadsides. It can tolerate sandy, loamy, or clay soils, though it prefers well drained, moist soil.

Impacts:

The rapidly growing vines of old man’s beard can blanket the ground and can also cover trees and shrubs, blocking out light for those plants and causing trees to fall. Once a tree collapses, the plant continues to grow along the ground in layers several feet thick, preventing native plant regeneration below it.

Noxious Weed Listing:

Origin:

Asia, Europe, and North Africa

Links:

Oregon Noxious Weed Profile
Washington Noxious Weed Profile
CABI Invasive Species Compendium
4 County CWMA Weed Profile
Global Invasive Species Database

 

English Hawthorn (Crataegus monogyna)

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Common names:

English hawthorn, common hawthorn, singleseed hawthorn, oneseed hawthorn

Scientific Name:

Crataegus monogyna

Description:

English hawthorn is a deciduous small tree or large shrub in the Rosaceae (rose) family. While it was introduced to North America in the 1800s, it has only recently become a problem on the West Coast. Hawthorn branches have many stout spines and its bark is smooth, pale, and gray. The leaves are alternate, leathery, and deeply lobed. The flowers grow in clusters of 10 – 20, are white with a pink tint, and have 5 petals. The plant also has clusters of single-seeded red berries. Seeds are widely dispersed by birds.

Life cycle:

Perennial

Height of mature plants

10 to 30 feet

Flower color:

White

Bloom time:

May

Look-a-likes:

English hawthorn looks similar to the native black hawthorn. The leaves of black hawthorn are only weakly lobed, and the fruits are blackish, rather than bright red.

Habitat:

English Hawthorn grows in many soil types, but seems to prefer moist disturbed places. In its native range, it often grows as a forest understory species. Here in Oregon, it can be found growing in riparian areas, pastures, woodlands, forests, and abandoned fields. Once established, it can survive moderate drought conditions

Impacts:

English hawthorn can grow in thorny thickets that suppress native vegetation an dmake it difficult for wildlife movement. It is also hybridizing with the native hawthorn, which can decrease the native hawthorn population and may create a weedier, more competitive variety. Birds may prefer its berries to those of native berried plants, which may cause a reduction in the regeneration of native plants.

Noxious Weed Listing:

Origin:

Europe, North Africa, West Asia,

Links:

Washington Noxious Weed Profile
King County Noxious Weed Profile
CABI Invasive Species Compendium

Poison Hemlock (Conium maculatum)

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Common names:

Poison hemlock, fool’s parsley, spotted hemlock

Scientific Name:

Conium maculatum

Description:

Poison hemlock is a very tall biennial plant in the Apiaceae (carrot) family.  It grows as a rosette the first year, and then flowers the next year. It has a deep taproot and the stems are hollow, hairless, with distinctive purple spots. The leaves are alternate, fern-like and finely divided. The white flowers grow in umbrella shaped clusters that are about 4 – 8 inches across. It spreads solely by seed and each plant can produce anywhere from 1,500 to 39,000 seeds that can live in the soil for up to six years. Seeds are dispersed by water, wind, animal fur, human clothing, boots, and machinery.

Life cycle:

Biennial

Height of mature plants

Up to 12 feet

Flower color:

White

Bloom time:

May – September

Look-a-likes:

Poison hemlock looks like several other members of the carrot family. The closest look alike is wild carrot, but wild carrot is smaller than poison hemlock and does not have purple spots on the stem.

Habitat:

While poison hemlock prefers moist, rich soils, it can easily adapt to other conditions and will grow in pastures, waste areas, riparian zones, ditches, and fencerows. It does not grow well in acidic soils and heavy shade.

Impacts:

Poison hemlock can quickly invade large pastures and riparian areas, reducing forage quality, poisoning livestock, and outcompeting other plants. This plant is considered one of the most poisonous plants in North America as the entire plant (especially the root and crown) is toxic to both humans and animals. Several livestock deaths are attributed each year to this species. Wear gloves when handling this plant, as it is also a skin irritant.

Noxious Weed Listing:

Origin:

Asia, Europe, and North Africa

Links:

Oregon Noxious Weed Profile
Washington Noxious Weed Profile
Invasive.org profile
CABI Invasive Species Compendium

Meadow Knapweed (Centaurea x moncktonii)

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Common names:

Meadow Knapweed

Scientific Name:

Centaurea x moncktonii (syns: C. pratensis, C. jacea x nigra, C.nigra var. radiata, C. debeauxii)

Description:

Meadow knapweed is an herbaceous perennial in the Asteraceae (sunflower) family. It is a hybrid between black knapweed (C. nigra) and brown knapweed (C. jacea), and thus it can have variable characteristics. It grows from a taproot and a woody crown. The leaves of the rosette can be lobed or unlobed and are slightly hairy, while the stem leaves are linear or slightly lobed and up to 6 inches long, growing smaller as they near the top of the plant. The lower leaves are longstalked, while the upper leaves have no stalks. Flowers are purple to pink to white and are solitary at the tip of branches. A key-identifying feature is the brown brushy-fringed bracts on the flower head.

Life cycle:

Short-Lived Perennial

Height of mature plants

3 feet (but varies from 1 to 5 feet)

Flower color:

pink, purple, white

Bloom time:

May – August

Look-a-likes:

Meadow knapweed can be confused with other knapweeds, especially spotted knapweed. However, the bracts on meadow knapweed are brown and papery with fringed bracts. The leaves are also less lobed than spotted knapweed. If you need help with plant identification, please contact your county noxious weed coordinator.

Habitat:

Meadow knapweed can grow in a wide variety of habitats, from fields and prairies to riverbanks and moist meadows. It can also be found growing along roadsides, in forest openings, clearcuts, industrial sites and tree farms.

Impacts:

Meadow knapweed can spread aggressively in pastures and meadows and it will outcompete native plants and desirable forage plants (though sheep find it desirable). Seeds can remain viable in the soil for 5 years, it has a tough perennial root system, and it can resprout from root crowns, making it difficult to control.

Noxious Weed Listing:

Origin:

Europe

Links:

Oregon Noxious Weed Profile
Washington Noxious Weed Profile
Invasive.org profile
CABI Invasive Species Compendium

 

Spotted Knapweed (Centaurea stoebe)

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Common names:

Spotted Knapweed

Scientific Name:

Centaurea stoebe (syns: C. maculosa, C. stoebe ssp. micranthos)

Description:

Spotted knapweed is a biennial or perennial in the Asteraceae (sunflower) family. It spreads aggressively, has spread across most of the continental United States and Canada, and is considered one of the most dominant weeds in the western United States. The plant has multiple stems with alternate leaves that are blue-gray and unlobed in the upper portion of the plant and lobed on lower areas. Flowers are pink to purple (sometimes cream-colored), with bracts that are black-tipped, giving it a spotted appearance. Seeds disperse easily through wind, water, livestock, wildlife, and human activity.

Life cycle:

Biennial or short-lived perennial

Height of mature plants

3 to 5 feet

Flower color:

pink to lavender (occasionally cream)

Bloom time:

June to November

Look-a-likes:

There are many other knapweed species that can be difficult to distinguish from each other. The black triangular spots on the bract tips below the flower head are an important feature for identifying spotted knapweed. If you need help with plant identification, please contact your county noxious weed coordinator.

Habitat:

Spotted knapweed often grows in dry areas including meadows, pastures, rocky areas, gravel sites, railroads, roadsides, vacant lots, and forest clearings. It can also invade sandy or gravelly floodplains.

Impacts:

Spotted knapweed can quickly colonize disturbed land and roadsides. It is a prolific seed-producer, with 1000 seeds per plant that can live 8 years in the soil. Infestations of spotted knapweed decrease plant diversity and create wildfire hazards. Spotted knapweed has become a major agricultural issue and the costs to control this plant can create problems for land owners. Oregon infestations are broadly scattered though increasing, causing economic losses to right of way maintenance, grazing and range productivity.

Noxious Weed Listing:

Origin:

Europe

Links:

Oregon Noxious Weed Profile
Washington Noxious Weed Profile
Invasive.org profile
CABI Invasive Species Compendium
Global Invasive Species Database

Wild Chervil (Anthriscus sylvestris)

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Common names:

wild chervil, cow parsley, wild beaked parsley, keck, Queen Anne’s lace

Scientific Name:

Anthriscus sylvestris

Description:

Wild chervil is an herbaceous biennial or short lived perennial in the Apiaceae (carrot) family. It is upright and grows aggressively, so it can shade out native plants. It grows from a taproot and the stems are hollow, ridged, and hairy on the lower portions. The leaves are alternate, very finely divided, fern-like, and slightly hairy. The flowers are small and white with 5 petals, and they grow in umbels (umbrella shape) that can be about 3 inches wide. It spreads by seeds that are transported by wind, animals, people, and vehicles.

Life cycle:

Biennial or short-lived perennial

Height of mature plants

1 to 4 feet

Flower color:

White

Bloom time:

April – June

Look-a-likes:

Wild chervil looks quite similar to wild carrot and poison hemlock as all three plants have fernlike leaves, a taproot and white umbel flowers. A distinguishing feature of wild chervil is the presence of ridges on the stems. Compared to poison hemlock, it is smaller and lacks the odor.

Habitat:

Wild chervil grows in open sunny areas including agricultural areas, open disturbed areas, roadsides, pastures, and yards. It can tolerate many soil types and low to high light intensities.

Impacts:

Wild chervil grows fast and is large, so it outcompetes other plants for sunlight and other resources. It creates monocultures that threaten native plants, crops, and agriculture.

Noxious Weed Listing:

Origin:

Europe

Links:

Washington Noxious Weed Profile
Thurston County profile
Invasive.org Profile

 

Tree of Heaven (Ailanthus altissima)

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Common names:

tree of heaven, stinking quassia, copal-tree, China-sumac, varnishtree

Scientific Name:

Ailanthus altissima

Description:

Tree of heaven is a fast growing deciduous tree in the Simaroubaceae family. Its leaves are compound and alternate with anywhere from 10 to 45 leaflets. Flowers grow in large clusters and are light green to yellow. Each seed is encased in a slightly twisted papery wing. The bark on young branches is yellow-brown, while older bark is gray. The tree has a foul odor, reminiscent of rancid peanut butter.

Life cycle:

Perennial

Height of mature plants

25-50 feet

Flower color:

Light green to yellow

Bloom time:

May – June

Look-a-likes:

Tree of Heaven is sometimes mistaken for sumac, walnut, or hickory. Two of its distinguishing features are the prominent leaf scars on the twigs and the foul peanut butter odor.

Habitat:

Tree of heaven grows in many habitat types, though it prefers sunny disturbed areas. It can invade roadsides, forest edges, woodlands, fields, urban parks and riparian areas. It can grow in disturbed areas with poor soils, and can sometimes be found growing in cement cracks.

Impacts:

Tree-of-heaven creates problems in natural systems by forming large thickets via root suckering. Riparian areas are especially affected. Western Oregon populations invade road rights-of-way, parks, and private property. Its growth outpaces many native trees, which reduces the biodiversity of important habitats. Lateral rooting can push up pavement and sidewalks and has been noted to ruin septic tank drain fields in its search for moisture. It produces large numbers of seeds and vigorously resprouts after cutting, making control difficult. Herbicide applications while the tree is leafed out have been minimally successful.

Noxious Weed Listing:

Origin:

China and Taiwan

 Links:

Oregon Noxious Weed Profile
Washington Noxious Weed Profile
Invasive.org profile
CABI Invasive Species Compendium
Global Invasive Species Database

 

Garden loosestrife (Lysimachia vulgaris)

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Common names:

Garden loosestrife, garden yellow loosestrife,

Scientific Name:

Lysimachia vulgaris

Description:

Garden loosestrife is a tall upright rhizomatous noxious weed that grows up to 5 feet in height.  It is characterized by terminal panicles of bright yellow 5-petaled flowers.  Leaves are opposite to whorled, nearly sessile and lanceolate 7-12 cm in length.  The stems and leaves are soft and hairy.  Flowered are ringed by distinctive orange-margined green sepals. Underground rhizomes can spread to lengths up to 15 feet.  Plants reproduce from both rhizomes and seeds.

Life cycle:

Perennial

Height of mature plants

3 to 6 feet

Flower color:

Yellow 5- petaled flower, that lack reddish or black streaks or dots

Bloom time:

Typically blooms during July and August.

Look-a-likes:

The closely related Yellow loosestrife (Lysimachia punctata) is a less aggressive garden ornamental, with lower flowers from emerging from the leaf axils, and the yellow flowers lack the orange-margined sepals, characteristic of the noxious garden loosestrife.

Habitat:

Garden loosestrife is found escaping in wetlands and along streams and river.  It is also likely to be found in garden setting.  This species is known to occur in only one location in Oregon.

Impacts:

Garden loosestrife invades wetland and riparian areas, where it displaces desirable native vegetation.  Once established it can spread rapidly, and has been known to displace very hearty plants such as cattails.  Invasion by garden loosestrife disrupts habitat for fish and wildlife, and can limit recreation opportunities in highly invaded sites.

Noxious Weed Listing:

Origin:

This species is native to Europe.

Present in Clackamas County:

No

Links:

Oregon Noxious Weed Profile

USDA Plants

King County Noxious Weed Program

Invasive Plant Atlas of New England

 

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