Garlic mustard (Alliaria petiolata)
Garlic mustard (Alliaria petiolata)
Garlic mustard (Alliaria petiolata)
Garlic mustard (Alliaria petiolata)

Description
Biennial. Rosettes form by midsummer the first year; blooms May to June the second year. Grows an average of one to three feet tall. Basal leaves are dark green, kidney-shaped, scalloped and two to four inches in diameter. Stem leaves alternate, are sharply toothed, triangular, get smaller toward the top of the stem, and produce a distinct garlic odor when crushed. Flower stalks are usually single and unbranched. Flowers are one-quarter inch wide with...

Giant hogweed (Heracleum mantegazzianum)
Giant hogweed (Heracleum mantegazzianum)
Giant hogweed (Heracleum mantegazzianum)
Giant hogweed (Heracleum mantegazzianum)

Description
Perennial, flowers May to July. Grows 10 to 15 feet tall. Stalk and flower head develop after two to four years, then the plant dies back. Stalks are two to four inches in diameter, hollow, have reddish-purple blotches and pustules with a single, erect hair in the center. Flower head is a large, umbrella-like inflorescence up to two and one half feet in diameter. Leaves are three to five feet wide, compound and deeply incised. This plant closely...

Giant knotweed (Polygonum sachalinense)
Giant knotweed (Polygonum sachalinense)
Giant knotweed (Polygonum sachalinense)
Giant knotweed (Polygonum sachalinense)

Description
Perennial, blooms July to October. Grows over 12 feet tall. Closely related and similar to Japanese knotweed. Leaf is cordate, or heart shaped; it often exceeds one foot long. Inflorescence of creamy white flowers is sparse, and the flower size does not increase with maturity. Hybrids with Japanese knotweed are common. Japanese knotweed is smaller, with truncate leaves.

Impacts
Giant knotweed is the largest of the...

Goatsrue (Galega officinalis)
Goatsrue (Galega officinalis)
Goatsrue (Galega officinalis)
Goatsrue (Galega officinalis)

Other common names
American garden rue, Catgut, Devil's shoestring, Rabbit-pea, Horey turkey peas, Virginia pea, Virginia tephrosia, Professor weed

Description
Deep-rooted perennial, regrowing each year from a crown and taproot, reaching 2 to 6 feet tall by late summer. Plants may have up to 20 hollow stems. The first seedling leaves are large, oval and dark green. The mature leaves are alternate, odd-pinnate with 6 to 10 pairs...

Gorse (Ulex europaeus)
Gorse (Ulex europaeus)
Gorse (Ulex europaeus)

Description
Perennial, blooms March to May. Grows one to nine feet tall. A stiff, spiny, much-branched shrub, often forming dense thickets. Branches are dark green, spine-tipped, with clusters of yellow, pea-like flowers near the ends.

Impacts
Gorse is a persistent, spiny pioneer species adapted to a wide range of environmental conditions. Plant growth and stand density increase at a rapid rate, crowding out native plants, impacting...

Hairy white top (Cardaria pubescens)
Hairy white top (Cardaria pubescens)
Hairy white top (Cardaria pubescens)
Hairy white top (Cardaria pubescens)

Description
Perennial, blooms April to October. Grows up to two feet tall. Leaves are three inches long and one inch wide, often smaller. Hairs are sparse. Petals are white, mostly 2 to 3.5 millimeters long. Pods are strongly inflated, spherical to ovoid, and covered with short hairs. Hairy whitetop is difficult to distinguish from Hoary cress in the vegetative state.

Impacts
A common weed species on alkaline soils but not restricted...

Halogeton (Halogeton glomeratus)
Halogeton (Halogeton glomeratus)
Halogeton (Halogeton glomeratus)
Halogeton (Halogeton glomeratus)

Description
Annual, blooms July to September. Grows a few inches to 1 1/2 feet tall. Main stems branch from the base, spreading at first and then becoming erect. Plants are blue-green in spring and early summer, turning red or yellow by late summer. Leaves are small, fleshy, nearly tubular and tipped with a needle-like spine. Flowers are inconspicuous and borne in the leaf axils.

Impacts
Native to Asia with a wide distribution...

Heartleaf hempvine (Mikania cordata)

Description
Perennial vine, grows 9 to 18 feet long. Leaves are opposite, heart-shaped, and 1 to 5 inches long. Flowerheads are flat-topped clusters of four yellowish-white flowers. Seeds are small, plumed and brownish-black. 

Impacts
Grows in moist, disturbed areas. It will grow in partial shade but cannot tolerate dense shade. It has the potential to rapidly crowd out native vegetation if introduced to suitable habit...

Herb Robert (Geranium robertianum)
Herb Robert (Geranium robertianum)
Herb Robert (Geranium robertianum)
Herb Robert (Geranium robertianum)

Other common names
Herb Robert, Robert Geranium, Stinky Bob, Red Robin, Fox Geranium

Description
A branching, low-growing winter and spring annual. It has light-green leaves that are deeply dissected and release a pungent odor, making this plant easy to recognize. As the plants mature, the foliage turns red. This red color is very noticable under bright light conditions. The stems are highly pubescent, have multiple forks, and are...

Himalayan blackberry (Rubus discolor)
Himalayan blackberry (Rubus discolor)
Himalayan blackberry (Rubus discolor)
Himalayan blackberry (Rubus discolor)

Description
Perennial, blooms June to August. Root buds produce trailing, reddish stems with sharp spines that can grow more than 20 feet per season. Leaves alternate, and are palmate and compound with serrate margins. Flowers are five-petaled, white to light pink. Fruits aggregate.

Impacts
Himalayan (also called Armenian) blackberry is the most widespread and economically disruptive of all the noxious weeds in western Oregon. It...