Stemless thistle (Onopordum acaulon)
Stemless thistle (Onopordum acaulon)
Stemless thistle (Onopordum acaulon)

Description
Nearly stemless, with the stalks rarely exceeding 10 centimeters in length. The short-stalked leaves are 15 to 38 centimeters long, deeply dissected into spine-toothed lobes, narrow and oblong, grey or white, and hairy on both surfaces. The flower heads are white or purple, and form at the center of the basal rosettes of foliage. Seeds are grey-brown and about 4 millimters long. They are four-sided, pitted and ridged lengthwise, with a pappus of cream-...

Sulfur cinquefoil (Potentilla recta)
Sulfur cinquefoil (Potentilla recta)
Sulfur cinquefoil (Potentilla recta)
Sulfur cinquefoil (Potentilla recta)

Description
Perennial, blooms May to June. Grows 1 to 1 1/2 feet tall. Leaves are compound with 5 to 7 leaflets on each leaf. Flowers are light yellow with 5 petals.

Impacts
This plant is a problem weed in disturbed areas such as roadsides and pastures and in old fields in northeastern Oregon. It is occasionally found in cultivated fields. Sulfur cinquefoil can be found replacing Yellow starthistle in areas where moisture is adequate...

Swamp stonecrop (Crassula helmsii)
Swamp stonecrop (Crassula helmsii)
Swamp stonecrop (Crassula helmsii)

Description
Aquatic or semiterrestrial, succulent, perennial herb that grows 10 to 130 centimeters long. Round stems are floating or creeping, with roots forming at the nodes. Leaves are opposite, sessile and succulent. They are 4 to 20 millimeters long, 0.7 to 1.6 millimters wide, linear-lanceolate to ovate-lanceolate, and acute. It has white or pinkish flowers that are borne singly in the axils of leaves. Inflorescences have a diameter of 3 to 3.5 millimeters....

Syrian bean caper (Zygophyllum fabago)
Syrian bean caper (Zygophyllum fabago)
Syrian bean caper (Zygophyllum fabago)

Description
Perennial that may act like an annual in regions with harsh winters. Flowers April to June. Grows up to 1 1/2 feet tall. Leaves are somewhat succulent, opposite and compound, with each having 2 oval, 1-inch leaflets. Stems are smooth and thickened. Flowers are borne singly or in pairs from the leaf axils, and are salmon to yellow or white with pinkish veins.

Impacts
Syrian bean caper is well suited to dry environments....

Tansy ragwort (Senecio jacobaea)
Tansy ragwort (Senecio jacobaea)
Tansy ragwort (Senecio jacobaea)
Tansy ragwort (Senecio jacobaea)

Other common names
Stinking willie, Ragwort, Tansy butterweed, Stinking davies, Stinking ninny, Tansy ragweed

Description
Biennial or short-lived perennial, blooms midsummer to fall. Grows 1 1/2 to 6 feet tall. Leaves are dark-green and deeply lobed. Numerous seed heads, each with multiple, yellow, multi-rayed flowers. Reproduces by seed only, but can all-regenerate vegetatively if grazed or mowed and moisture conditions are right....

Taurian thistle (Onopordum tauricum)
Taurian thistle (Onopordum tauricum)
Taurian thistle (Onopordum tauricum)
Taurian thistle (Onopordum tauricum)

Other common names
Bull cottonthistle

Description
A vigorous biennial or short-lived perennial with coarse, spiny leaves and conspicuous spiny-winged stems. Plants are a nearly florescent lime-green in color with large, mostly singular flower heads at the terminals of the main and side stems. The bright-purple flower heads are 3 to 4 inches in diameter. The heads consist of numerous spiny-tipped bracts resembling an artichoke before...

Texas blueweed (Helianthus ciliaris)
Texas blueweed (Helianthus ciliaris)
Texas blueweed (Helianthus ciliaris)
Texas blueweed (Helianthus ciliaris)

Other common names
Blueweed, Yerba parda

Description
Perennial, blooms in mid summer. Grows 1 to 2 feet tall. Stems arise from woody, creeping roots. Leaves mostly opposite, narrow to broadly lance-shaped, margins wavy, often with hairs. Flower heads comprised of yellow outer ray flowers and reddish to dark-purple inner disk flowers.

Impacts
This plant is native to the southwestern U.S. and can be...

Tropical soda apple (Solanum viarum)
Tropical soda apple (Solanum viarum)
Tropical soda apple (Solanum viarum)
Tropical soda apple (Solanum viarum)

Description
Perennial, shrubby forb that grows up to 6 feet in height and width. Leaves are broad, 6 to 8 inches long, 2 to 6 inches wide, hairy and resemble fig or oak leaves. The entire plant is armed with ¾ inch-long straight prickles. Flowering occurs year-round, with most reproduction occurring from September to May. White, 5-petaled flowers develop, in clusters, below the leaves. Fruit are 1 inch in diameter and resemble a watermelon (a mottled mix of...

Turkeyberry (Solanum torvum)
Turkeyberry (Solanum torvum)
Turkeyberry (Solanum torvum)
Turkeyberry (Solanum torvum)

Other common names
Susumber, Gully-bean, Thai eggplant, Devil’s fig

Description
Broad-leaved, evergreen shrub or small tree that invades a variety of ecosystems. Plants can grow up to 16 feet tall. The stems are armed with stout prickles, which are straight or lightly curved. The alternate leaves are elliptical, 10 inches long, have prickles along the midvein and star-shaped hairs underneath. Leaves range from unlobed to...

Velvetleaf (Abutilon theophrasti)
Velvetleaf (Abutilon theophrasti)
Velvetleaf (Abutilon theophrasti)

Description
Annual, blooms June to October. Grows from two to seven feet tall. Completely covered in soft hairs. Leaves are alternate, heart-shaped, and five or more inches wide. Flowers are yellow, five-petaled and solitary in leaf axils.

Impacts
Velvetleaf has been a serious weed in corn and soybeans, but newer herbicides have allowed for better control. It is commonly found in cultivated fields, gardens, fencerows and waste areas...