Scotch broom (Cytisus scoparius)
Scotch broom (Cytisus scoparius)
Scotch broom (Cytisus scoparius)

Description
Perennial, blooms April to June. Grows 3 to 10 feet tall. Evergreen shrub with many slender, erect, dark green, angled branches with small, simple leaves. Abundant small, yellow, pea-shaped flowers. Easily confused with Spanish broom. Spanish broom (S. Junceum) has round stems, very few leaves, and larger yellow flowers.

Impacts
Scotch broom is a pioneer species known to displace native plant species and increase the...

Scotch thistle (Onopordum acanthium)
Scotch thistle (Onopordum acanthium)
Scotch thistle (Onopordum acanthium)
Scotch thistle (Onopordum acanthium)

Description
Biennial that sometimes acts like an annual, blooms May to June. Often producees a rosette the first year; when acting like an annual it can grow 2 to 4 feet the first year, and is capable of heights over 10 feet in the second year. Large amount of soft, white hair on upper leaf surface. Towering height, depending on available moisture. Winged tissue along the stem. Purple flower. Stands are dense and practically impenetrable because of spiny nature and...

Senegal tea plant (Gymnocoronis spilanthoides)
Senegal tea plant (Gymnocoronis spilanthoides)
Senegal tea plant (Gymnocoronis spilanthoides)

Description
Freshwater or marsh-growing emergent perennial herb that forms rounded bushes up to 1 meter tall or scrambling mats of tangled stems along the edges of waterways. Young stems are 5 to 10 millimeters in diameter, and mature stems 20 millimeters in diameter. Larger stems are hollow between the nodes (the joints between segments of stem) and float on water, reaching lengths of 1.5 meters. The leaves are dark green, 50 to 200 millimters long, and arranged in...

Serrated tussock (Nassella trichotoma)
Serrated tussock (Nassella trichotoma)
Serrated tussock (Nassella trichotoma)

Description
Perennial, tussock-forming grass that can live for more than 20 years. It has a deep, fibrous root system and is very difficult to pull from the ground. It grows to a height of 70 centimeters with an overall diameter of about 70 centimeters. The leaves are narrow (about 0.5 millimters in diameter) and tightly rolled, without hairs but with small easily-felt serrations along their lengths. The slender, open, branching flower heads (called panicles)...

Shiny geranium (Geranium lucidum)
Shiny geranium (Geranium lucidum)
Shiny geranium (Geranium lucidum)
Shiny geranium (Geranium lucidum)

Other common names
Shiny-leaf geranium, Shiny-leaf hawksbill

Description
Grows predominantly as an annual weed, though it may become biennial depending on moisture conditions. In Europe, it is described as growing up to 0.5 meters high and being very shade intolerant. Here in the Pacific Northwest, it is predominantly a forest understory species, very shade tolerant and only seen up to 10 to 12 inches high. Stems are red, growing...

Silverleaf nightshade (Solanum elaegnifolium)
Silverleaf nightshade (Solanum elaegnifolium)
Silverleaf nightshade (Solanum elaegnifolium)

Description
Perennial, flowers from midsummer to frost. Grows 1 to 3 feet tall. Leaves are narrow and, along with the stems, covered with dense hairs that give the foliage a gray or silvery appearance. Flowers are violet to light- blue, 3/4 to 1 inch wide. Fruit is a yellow or dull orange berry, which may eventually turn blackish.

Impacts
This plant is found in rangeland, pastures, waste areas and cropland in the western U.S. The...

Skeletonleaf bursage (Ambrosia tomentosa)
Skeletonleaf bursage (Ambrosia tomentosa)
Skeletonleaf bursage (Ambrosia tomentosa)

Other common names
Bur ragweed, Silverleaf, Povertyweed

Description
Perennial, flowers June to August. Grows 4 to 18 inches tall with extensive creeping rootstocks. Leaves are lanceolate, coarsely toothed and deeply lobed. Flowers are inconspicuous and yellow. Fruit is a light-brown bur with spines.

Impacts
Skeletonleaf bursage grows in cultivated fields, pastures and waste areas in several western...

Slender-flower thistle (Carduus tenuiflorus)
Slender-flower thistle (Carduus tenuiflorus)
Slender-flower thistle (Carduus tenuiflorus)

Other common names
Shore thistle

Description
Annual or sometimes biennial, blooms May to June. Grows 1 to 4 feet tall. Stems have spiny wings. Leaves are deeply cut into 2 to 5 pairs of lobes, and the undersurface is slightly woolly. Flowers are purplish to pinkish, borne in cylindrical heads either solitary or in clusters of 2 to 5. Bracts are hairy. Fruits from the outer part of the flower head are gray, and from the inner portion...

Small broomrape (Orobanche minor)
Small broomrape (Orobanche minor)
Small broomrape (Orobanche minor)
Small broomrape (Orobanche minor)

Description
Annual, blooms within a week of plant emergence. Grows 6 to 20 inches tall. Lacks chlorophyll. Has yellowish-brown, unbranched stems with a purplish tint. Leaves look like small triangular scales. Flowers are pinkish, yellow or white and arranged in an elongated terminal cluster.

Impacts
Small broomrape is a parasitic plant. Upon germination, the first root attaches to and penetrates the root of the host plant, usually...

Smooth cordgrass (Spartina alterniflora)
Smooth cordgrass (Spartina alterniflora)
Smooth cordgrass (Spartina alterniflora)
Smooth cordgrass (Spartina alterniflora)

Description
This perennial, aquatic grass grows erect up to 5 feet tall. When fresh, the leaves are flat without prominent mid-rib and taper to a sharp tip. Stems are round with joints, hollow between the joints and often red at the base of healthy young plants. The roots are white and fleshy with underground runners (rhizomes) that spread aggressively. Flowers are arranged in compact spikes 10 to 20 cm long. Seeds are produced in the fall and can be carried away in...