Description:

Carex pendula is an exotic, clump-forming sedge. It grows in full to partial shade in moist soils and has long and drooping inflorescences. Please see below for additional identification resources as there are similar native species.

Life cycle:

Perennial

Height of mature plants

3-6 feet

Flower color:

Inconspicuous off-white flowers

Bloom time:

March through May

Look-a-likes:

There are several species present in our area that look similar to Carex pendula. Carex pendula belongs to a group of grass-like plants called sedges which, in general, are difficult to identify. Therefore, caution is advised when not experienced with this group of plants. After using this simplified resource, please consult an experienced Carex indentifier or technical manual such as the Flora of Oregon: Volume 1 or Field Guide to Sedges of the Pacific Northwest to confirm your identification. Also check out our plant identification resources.

Four key features need to be present to confirm your identification: dense tufts or clumped (cespitose) growth form, large plant size (culms and leaves), wide leaf blades, and long & drooping spikes. There are several species that have at least two of these characteristics including Carex amplifolia, Carex aquatilis var. dives, Carex cusickii, Carex obnupta, Carex hendersonii, Carex utriculata, and Scirpus microcarpus. Please review the below image gallery and chart that dissects each of these features and how Carex pendula compares with each look-a-like species. Species traits taken from Flora of Oregon: Volume 1 and field observations.

Carex pendula (left) and Scirpus microcarpus (right) growing adjacent to each other surrounded by reed canarygrass. Typically Scirpus microcarpus is rhizomatous, but single mature plants are also observed as indicated in this photo. Note the distinctly different inflorescence of Scripus microcarpus.

Scirpus microcarpus inflorescence

Carex pendula (left) and Scirpus microcarpus (right) growing adjacent to each other. These can be distinguished based on their growth form: Scirpus microcarpus is rhizomatous and Carex pendula is cespitose (clumping).

Carex pendula (top) and Scirpus microcarpus (bottom) growing adjacent to each other. These can be distinguished based on their growth form: Scirpus microcarpus is rhizomatous and Carex pendula is cespitose (clumping).

Carex pendula (right) and Scirpus microcarpus (left) have similar leaf blades in width and color of the upper leaf surface, but can be distinguished based on lower leaf surface. Carex pendula has a less reflective, dull gray-green leaf underside while Scirpus microcarpus has a very reflective, apple green leaf underside.

Carex pendula (left) and Scirpus microcarpus (middle) have similar leaf blades in width and are easily distinguished from the much smaller Carex obnupta (right).

Carex pendula (center) seedling growing among Carex obnupta (surrounding center seedling).

Carex obnupta has shorter drooping spikes than Carex pendula.

Carex pendula (forground) growing adjacent to a large forested patch of Carex obnupta (background).

This mature Carex pendula plant doesn’t appear to be growing in a cespitose manner, however, the lower leaves are likely removed by floodwaters and covered by deposited sediment.

Carex amplifolia with ascending to spreading spikes.

Carex aquatilis var. dives has shorter drooping spikes than C. pendula. Photo © 1998, Fred Weinmann

Habitat:

C. pendula is known to affect wetlands, streamsides, roadsides, and adjacent forested habitats in Oregon.

field edge

among restoration plantings

floodplain bench

cobble bar in small stream

marshy detention pond

small floodplain of small creek

streambank

floodplain

roadside

Impacts:

Carex pendula has been observed in Clackamas County displacing native species along streams where in some cases it formed stands of 85% dominance. Assessing the distribution, impacts and potential impacts of this species requires more work and is a current project of the District.

Noxious Weed Listing:

• WeedWise: Priority
• State of Oregon: Watch
• State of Washington: Not listed
• Four County CWMA: Watch
• City of Portland: Class A

Origin:

Europe, North Africa

Links:

Invasive.org profile
CABI Invasive Species Compendium
USDA APHIS Weed Risk Assessment for Carex pendula

Description:

The plant is usually a winter annual, sometimes biennial, though it may germinate in all seasons. It grows from 4 to 18 inches tall. Flowerheads are numerous, with yellow disk flowers, but no ray flowers. The heads are cylindrical, 1/4 to 1/2 inch long, with black-tipped bracts around the base. Leaves are deeply lobed with toothed margins and may be smooth to hairy. They have little, or no, stalks and are alternately arranged on the stem. Basal leaves are usually purplish on the under surface, 1 to 4 inches long and 1/2 to 1-1/2 inches wide.

Life cycle:

Annual, Biennial

Height of mature plants

Up to 3.5 feet

Flower color:

Yellow

Bloom time:

Throughout the year

Look-a-likes:

A similar species is woodland groundsel (Senecio sylvaticus). This plant generally is larger, growing up to 3 1/2 feet tall, with leaves more deeply lobed than those of common groundsel. Leaves are greenish gray and woolly. They are largest near the base of the plant, becoming increasingly smaller toward the top. The plant has a nauseating odor when bruised. Woodland groundsel more often is found along roads and in disturbed areas in the forest, while common groundsel is a weed of fields and gardens and the waste areas nearby.

Habitat:

This weed is found in many crops including forages, cereals, mint, berries, and row crops, as well as in ornamentals and vegetable gardens.

Impacts:

Common groundsel is a problem weed in cultivated crops, gardens and nurseries. It is poisonous to cattle and horses and toxic to humans. It contains pyrrolizidine alkaloids, which can cause irreversible liver damage and possibly death.

Noxious Weed Listing:

• WeedWise: Maintenance
• State of Oregon: Not listed
• State of Washington: Class C
• Four County CWMA: Class D

Origin:

Europe, Asia and Northern Africa

Links:

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

Description:

Annual; blooms within a week of plant emergence. Like other parasitic plants, small broomrape lacks chlorophyll. The flower stalk is yellowish-brown, unbranched with a purplish tint. Leaves look like small triangular scales. Flowers pinkish, yellow or white in color and arranged in an elongated spike.

Life cycle:

Annual

Height of mature plants

6 to 12 inches

Flower color:

Pink, Yellow, White

Bloom time:

December through April

Look-a-likes:

Habitat:

This species primarily impacts areas under cultivation of clover in our area, but is also associated with disturbed areas, other crops, roadsides and waste places on a wide range of soil types.

Impacts:

Upon germination, the first root attaches to and penetrates the root of the host plant, usually clover and other legumes, disrupting nutrients and water transport in the host root system. It has the ability to produce up to 500,000 seeds per plant that are dispersed by wind, tillage equipment, harvesters, commodity movement and animals. An uprooted flowering plant will continue to produce seed. Heavy infestations can cause severe crop damage that may result in nearly total crop failure. It is especially problematic in clover crops where the Orbanche seeds are hard to detect or remove during mechanical cleaning of harvested seed.

Noxious Weed Listing:

• WeedWise: Maintenance
• State of Oregon: Class B
• State of Washington: Not listed
• Four County CWMA: Class D
• Columbia Gorge CWMA: Class A

Origin:

Europe, North Africa and western Asia

Links:

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

Description:

Lesser celandine is an herbaceous, perennial plant in the buttercup family. It has a basal rosette of dark green, shiny, stalked leaves that are kidney to heart-shaped. It has eight glossy, butter-yellow petals, and is borne singly on delicate stalks that rise above the leaves. Pale-colored bulblets are produced along the stems of the above ground portions of the plant, but are not apparent until late in the flowering period. When in bloom, large infestations of appear as a green carpet with yellow dots, spreading across the forest floor. There are many varieties of lesser celandine including a double-flowered form with many crowded petals and dark green leaves mottled with silvery markings. The primary reproductive method is the formation of turions that are produced on the roots in large numbers. They are easily moved in contaminated dirt or by water.

Life cycle:

Perennial

Height of mature plants

3 to 24 inches

Flower color:

Yellow

Bloom time:

March to April

Look-a-likes:

Marsh marigold (Caltha palustris) is a similar native species which grows in much wetter marshy habitats than lesser celandine.

Habitat:

It prefers shaded to partially shaded sites though it can thrive in full sun with adequate soil moisture. Deciduous woods are an excellent habitat for this species enabling the plant to grow and bloom well before leaf initiation in the forest canopy.

Impacts:

Lesser celandine forms dense patches leading to the exclusion of many low-growing forbs especially earlyblooming native wildflowers. Lesser celandine escaping from private plantings quickly overwhelm flowerbeds and lawns. Contaminated garden loam applied to new lawns can create problems in a few short years. Because of the bulbous nature of the root system, control can be difficult. Bulb fragments are easily overlooked during manual control, leading to reinfestation. Chemical control must be timed for optimal kill but the nonselective nature of certain herbicides can lead to nontarget impacts on desirable plants. Cultivars of lesser celandine continue to be sold through catalogs and nurseries nationwide.

Noxious Weed Listing:

• WeedWise: Maintenance
• State of Oregon: Class B
• State of Washington: Not listed
• Four County CWMA: Class B

Origin:

Europe

Links:

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

Description:

Evergreen blackberry is an upright to rambling evergreen, perennial, woody shrub with stout stems that possess stiff, sharp, recurved prickles. It may grow up to 13 feet and stems can be about 30 feet long. Plants grow into impenetrable thickets. Flowers are in clusters of 5 to 20. Each flower has 5 petals and 5 sepals. Petals are white to dark pink in color and are 3 lobed at the tips. Leaves are alternately arranged and generally made up of 5 leaflets that are deeply divided and lobed with toothed margins. Leaves are green to dark green in color. Leaf undersides have hairs.

Life cycle:

Perennial

Height of mature plants

10 feet

Flower color:

White

Bloom time:

June through July

Look-a-likes:

Himalayan blackberry (Rubus bifrons) is similar but does not have as deeply divided leaves.

Habitat:

It grows in a wide range of conditions including disturbed areas, pastures, forest plantations, roadsides, riparian areas, riverbanks and wetland edges.

Impacts:

Cutleaf blackberry outcompetes native vegetation and prevents the establishment of native trees that require sun for germination. It forms impenetrable thickets that block access to water and lacks the deep, bank stabilizing roots of native wetland shrubs and trees.

Noxious Weed Listing:

• WeedWise: Maintenance
• State of Oregon: Not listed
• State of Washington: Class C
• Four County CWMA: Class C

Origin:

Eurasia

Links:

Washington Noxious Weed Profile
Invasive.org profile

Description:

Curly-leaf pondweed grows entirely underwater except for the flower stalk which rises above the water. It has distinctly wavy-edged, crispy olive-green to reddish-brown leaves. It usually grows early in spring and dies back in summer. Flowers are tiny with 4 petal-like lobes and in spikes around 1 inch long from stalks that are up to 2.8 inches long. Leaves alternate, all submersed without leaf stalks. Leaves oblong, stiff, (1.6 to 3.9 inches long by 0.2 to 1 inch wide) with distinctly wavy edges with fine teeth and 3 main veins. It produces seeds, rhizomes and turions, but the importance of seed in the spread of populations is unknown and is assumed to be less important than turions. Typically it reaches peak biomass in the late spring/early summer months and forms turions.

Life cycle:

Perennial

Height of mature plants

N/A

Flower color:

Bloom time:

April through May

Look-a-likes:

None

Habitat:

It grows in shallow to deep, still or flowing water and is tolerant of disturbance.

Impacts:

It is an invasive plant that forms surface mats, interfering with aquatic recreation. Dense colonies can restrict access to docks and sport fishing. Curly-leaf pondweed has been noted as one of the most severe nuisance aquatic plants in the Midwest.

Noxious Weed Listing:

• WeedWise: Maintenance
• State of Oregon: Not listed
• State of Washington: Class C
• Four County CWMA: Class C
• Columbia Gorge CWMA: Class C

Origin:

Asia, Europe, Australia and Northern Africa

Links:

Washington Noxious Weed Profile
Invasive.org profile
CABI Invasive Species Compendium
National Invasive Species Information Center
Global Invasive Species Database

Description:

Common tansy is an aromatic perennial with rhizomes, reaching 1 to 5 feet tall, with fern like foliage and yellow button-like flowers. Flowerheads are numerous, button-like and yellow. They are 1/4 to 1/2 inches across in flat-topped dense clusters. Flowerheads composed of all disk flowers and are absent of ray flowers. Leaves are alternate and pinnately compound (leaflets arranged on both sides of a common stalk). They are deeply divided into numerous, narrow, toothed segments. Leaves become smaller towards the top of the stalk and are strongly aromatic when crushed.

Life cycle:

Perennial

Height of mature plants

1-5 feet

Flower color:

Yellow

Bloom time:

June through August

Look-a-likes:

Common St. Johnswort (Hypericum perforatum) and tansy ragwort (Senecio jacobaea) may be mistaken for common tansy. Common St. Johnswort flowers have 5 petals per flower while common tansy does not have any petals (ray flowers) and and tansy ragwort has on average of 13 ‘petals’ (ray flowers).

Habitat:

The areas most infested by Weed X are important places that people care about.  Weed X especially loves those particular places that are liked by all of these really cool native plants.  So watch for Weed X is these really specific important places.

Impacts:

Common tansy is reported to be poisonous to livestock, though it is seldom grazed due to its strong odor. It displaces forage plants, reduces wildlife habitat and species diversity.

Noxious Weed Listing:

• WeedWise: Maintenance
• State of Oregon: Not listed
• State of Washington: Class B
• Four County CWMA: Class C

Origin:

Asia and Europe

Links:

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

Description:

Blessed milkthistle is a sparsely branched thistle growing up to 6 feet tall and forming dense stands. It’s a tap-rooted biennial or annual that forms large rosettes followed by 2 inch purple blooms borne singly on unbranched, grooved and somewhat cottony stems. The leaves are oblong to lanceolate, hairless, shiny dark green with distinctive white patterns running along the veins, reaching up to 20 inches long and 10 inches wide. The white mottling gives the plant the appearance of having been drenched in milk, thus the common name of milkthistle. The leaf margins are tipped with spines up to 1/2 inch in length. Large rosettes can reach 3 feet in diameter. Its solitary, composite, red-purple flowers reach 2 inches in diameter and are surrounded by leathery, spiny, hairless bracts. The all-disk flowers are similar to other thistles, with large spines extending out in layers from under the pincushion flower head.

Life cycle:

Biennial

Height of mature plants

Up to 6 feet.

Flower color:

Purple

Bloom time:

April to October

Look-a-likes:

None

Habitat:

Blessed milkthistle can be found in full sun or part shade.  They typically grow in poorly managed pastures and on roadsides where nitrogen is high and disturbance regimes are frequent. This plant is also traded horticulturally and found in ornamental and medicinal gardens.

Impacts:

• Serious threat to livestock. Ingestion by livestock can cause nitrate poisoning and death.
• Forms dense stands that shade out forage species and exclude livestock.
• Spines can cause injury to people and livestock.
• Displaces native vegetation.

Noxious Weed Listing:

• WeedWise: Priority
• State of Oregon: Class B
• State of Washington: Class A
• Four County CWMA: Class A
• Columbia Gorge CWMA: Class A

Origin:

Southern Europe

Present in Clackamas County:

Yes

Links:

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

Description:

Japanese, giant, and their hybrid Bohemian knotweed are all closely-related rhizomatous, semi-woody shrubs with hollow stems and showy flowers. Dense colonies of these highly invasive plants form due to their vigorous growth and ability to reproduce vegetatively through rhizomes and stems. Large infestations are extremely difficult to eradicate. Knotweed species can reach more than 12 feet in height and have more than 40 stems per plant. Erect stems are often arched at the top of the plants and are grooved, thick, and swollen at the nodes. Stems are green to reddish-brown. Knotweed is an escaped ornamental which thrives in disturbed, moist soils. It spreads easily through waterways which can carry root and stem fragments.

Life cycle:

Perennial

Height of mature plants

15 feet

Flower color:

White

Bloom time:

July through October

Look-a-likes:

These three species can be differentiated by close examination of their leaves. Japanese knotweed has alternate, leathery, thick, oval-shaped leaves that are sharply tipped and square across the base. The leaves have few hairs, are 4-5 inches long on the stalks, and are sometimes reddish. Giant knotweed has alternate, leathery, lanceolate shaped leaves (pointed at both ends) with a heart-shaped base. These leaves are 12 inches across and 18 inches long on stalks, but can reach up to 2.5 feet long. There are few hairs on the underside veins and on the margins. Bohemian knotweed leaves have characteristics of both Japanese and Giant. They are bluntly tipped and usually have a square base.

Habitat:

Knotweed thrives in disturbed and moist soils. All species can be found in riparian and wetland areas, along roadsides, coastal forests, pastures, and open, upland areas with plenty of sunlight and moisture.

Impacts:

Knotweed forms dense thickets, shading out native plants and excluding native animals. It out-compete nearby vegetation for soil nutrients and light. Additionally, it decreases property values from the potential of asphalt, concrete, or foundation damage from the rhizome and the long-term investment in the management of the plants. Lastly, it can induce bank erosion and lower water quality.

Noxious Weed Listing:

• WeedWise: Maintenance
• State of Oregon: Class B
• State of Washington: Class C
• Four County CWMA: Class B

Origin:

eastern Asia

Links:

Japanese Knotweed Oregon Noxious Weed Profile
Giant Knotweed Oregon Noxious Weed Profile
Bohemian Knotweed – CABI Invasive Species Compendium
Japanese Knotweed – CABI Invasive Species Compendium