Lepidium draba

Lepidium draba, also known as whitetop, hoary cress, or Thanet cress, is a rhizomatous perennial flowering plant in the family Brassicaceae. It is native to western Asia and southeastern Europe and has been widely introduced elsewhere.

Description
Whitetop is a perennial herb that reproduces by seeds and by horizontal creeping roots. The stem is stoutish, erect or spreading, 10 to 80 cm tall, branched, covered sparsely with ash-colored soft hairs to heavily covered. The leaves are alternating, simple, and mostly toothed. The basal leaves are 4 to 10 cm, have a slight stem (petiole), and are long and flat, lance-shaped to egg-shaped, with the narrow end attached to the stalk. On the upper part of the stem the leaves are attached directly to the stalk (sessile), are 2 to 6.5 cm long, and are oblong or tapering the point, with broad bases that clasp the stalk. Whitetop has slightly domed flower clusters in which the individual flower stalks grow upward from various points off the branch to approximately the same height (corymb-like). The petals are white, clawed, and 3 to 5 mm long, about twice the length of the sepals. Typically, each flower has four petals.



Uses
Hoary cress was traditionally used for medicinal purposes, including anti-inflammatory and antibacterial treatments.

Distribution
It is native to western Asia and southeastern Europe and is an invasive species in North America, introduced by contaminated seeds in the early 1900s. Also known as Cardaria draba, hoary cress is a weed in much of south-east and south-west Australia as well. It has been suggested that native grasses from the Poa genera may be able to outcompete hoary cress in North America.

Other reading
Agriculture Research Service (1970) "Cardaria draba (L.) Deav." Selected Weeds of the United States Agriculture Research Service United States Department of Agriculture, Washington, DC, p. 200