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Native Wildflowers of the North Dakota Grasslands

GIF -- species photo

Hairy Rock Cress (Arabis hirsuta)


Every county in North Dakota likely has a population of hairy rock cress. Elsewhere, the plant is very widely distributed, being found from Quebec to Alaska south to Georgia and Arizona.

Hairy rock cress is either biennial (lives for two years) or perennial (long-lived and blooms each year). Stems, which often are purplish below, usually are single, but occasionally two or three arise from a tough, persistent base. North Dakota specimens are mostly about one to two feet tall and are hairy below and smooth on the upper parts. There is a basal rosette of about a dozen leaves about two to four inches long. Above these, lower stem leaves about two inches long clasp the stem and are toothed; upper leaves are progressively shorter and smooth-margined. Numerous tiny white flowers form at the top of the plant. Silques (seedpods) are threadlike and one to two inches long. They usually are erect and close to the stem.

Look for hairy rock cress in late May to July in gravelly native prairie. Plants seem to be more abundant where grazing is light. I could find no references to economic uses of this plant.

Hairy rock cress is a member of the mustard family (Brassicaceae), some of whose 2,500 members have been developed into food plants such as cauliflower, radish, turnip, and rutabaga, as well as many ornamentals. However, other mustards are troublesome weeds. The family gets its name from brassica, the Latin name of the cabbage.

Carl von Linne (Linnaeus), the Swedish father of modern plant taxonomy, named the genus in 1753, purportedly after some mustard found in Arabia. There are about 100 species of Arabis in the north temperate zone. The specific name hirsuta means "with rather coarse or stiff hairs" in botanical Latin. Linnaeus described hairy rock cress for science in 1772.


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