White Flowered Forbs

White Flowered Forbs
African rue
Broadleaved pepperweed
Field bindweed
Hary whitetop
Horehound
Lens-podded hoarycress
Onionweed
Oxeye daisy
Poison hemlock
White clover
White sweetclover
Whitetop

 

Whitetop
Cardaria draba (L.) Desv. (Mustard family, Brassicaceae)
 

Description

Multi-stemmed perennial forb, 18 to 20 inches tall; erect stems sparse to densely covered with simple short hairs; seed production is prolific; new shoots arise from buds on lateral roots or root fragments; establishes dense stands that exclude other vegetation.

Leaves: Gray-green, alternate, obovate, lanceolate, and oblong to elliptic; surfaces, especially lower, sparsely to densely covered with simple, short white hairs, margins irregularly toothed to entire; basal leaves short-stalked 3-1/2 inches long and 1-1/2 inches wide; sessile upper leaves are sparsely to densely hairy with rounded to acute-lobed bases that clasp the stem.

Flowers: Flowers March to July; inflorescences often flat- topped; small (3/16 inch long), fragrant, white 4-petaled, flowers are numerous; sepals are glabrous.

Fruits: Pods upside-down, heart-shaped to broadly ovate in outline, 1/8 to 3/16 inch long, 1/8 to 1/4 inch wide, glabrous; style persistent, 1/16 to 1/8 inch long at the apex; seeds 1 to 2 per chamber, ovoid, slightly flattened, reddish-brown, less than 1/8 inch long and 1/16 inch wide.

Habitat

Cultivated and disturbed or degraded moist sites in meadows, grassland, chaparral, woodland, forest, and riparian communities, and roadsides; generally grows on alkaline to saline soils, but tolerates many soil types and moisture conditions within elevations that generally range from 3,000 to 8,000 feet.

Propagation/Phenology

Reproduces vegetatively from creeping roots and less importantly by seed. Seedlings develop tap roots to a depth of 10 inches or more and lateral roots with shoot buds within 1 month. This species is an aggressive weed; mature plants develop extensive systems of persistent, deep vertical and horizontal roots to depths
of 6-1/2 feet or more. Root fragments generate new plants, but regeneration is poor in dry soils.

Comments

Native to central Asia; this species is difficult to distinguish from lens-podded hoarycress and hairy whitetop in the seedling and vegetative states. Arizona prohibited/restricted noxious weed and New Mexico Class A noxious weed.

Collage of images of whitetop

 
Forest Service Shield
Invasive plants and weeds of the national forests and grasslands in the southwestern region
Whitetop flower Whitetop plant Whitetop plants Whitetop fruit