Whitetop or Hoary Cress (Cardaria draba)

Status:

Listed Noxious Weed In Montana

History:

First Montana Specimen Collected 1

County:

Gallatin

Year:

1936

"These plants are native to the Middle East and the former USSR. The weed seeds were probably brought to this country with contaminated alfalfa seed. Whitetop was first identified in Gallatin County in 1916. It now infests about 32,000 acres across the state." (Elpel)

Habitat:

Plants grow in cultivated fields, waste areas, and often in the edges of forests.

Growth Habit:

Perennial herb, up to 24" tall, erect, becoming lodged with age.

Leaves:

Alternate, lance-shaped and slightly irregular, grayish-green, base of upper leaves
clasping stem.

Stem:

Stoutish, branched toward top.

Flower:

Small, white, 4 petals; numerous flower branches and dense flowers give plant a dense, white, flat-topped appearance.

Roots:

Extensive horizontally and vertically, frequent shoots arising from root stocks.

Seeds:

Reddish-brown, granular, egg-shaped, contained in heart-shaped pods.

Other Notes:

“It is a creeping perennial, which reproduces by seed and creeping roots. The extensive root system spreads horizontally and vertically with frequent shoots arising from the rootstock. It grows erect from 10 to 18 inches high and has a white color. The alternate leaves clasp the stem and are oval or oblong with toothed or almost smooth margins. The leaves are often covered with very fine white hairs. Each leaf is 1/2 to 2 inches long with blunt ends. The flowers are white, 1/8 inch across, and numerous in compact flattop clusters which give the plant its name. Each heart-shaped seedpod contains two oval, finely pitted, red-brown seeds each about 1/12 inch long.” (CWMA)

"Hoary cress is one of the earliest perennial weeds to emerge in the spring. Flowers are produced in late April and May. It grows in waste places, cultivated fields, and pastures, and is capable of vigorous grow on the irrigated, alkaline soils of the West." (CWMA, 7)