Northern Prairie Wildlife Research Center
Also sometimes called "stinking clover," Rocky Mountain beeplant likely once occurred in every county in North Dakota. The plant also ranges from Illinois and Missouri to Saskatchewan westward to Washington and southward to west Texas at elevations under 8,500 ft.
This plant is an erect, branched annual (reproduce from seed every year) that grows to about 3 ft. tall in our area. Each leaf has a stalk (petiole) and three narrow leaflets whose margins may be entire or minutely serrulate (toothed). Dozens of bright, pink to purplish flowers are crowded into rounded or rather elongate spikes. Flowers are about 1/2 inch long and atop long pedicels. The stamens (pollen-bearing organs) are longer than the flowers, giving the spikes a fuzzy appearance. Fruit is a narrow capsule up to 2 inches long that bears several to many dark, ovoid seeds.
Look for Rocky Mountain beeplant in early July on native prairie in light or sandy soils. I have found plants abundant on both lightly- and heavily-grazed pastures. The plant, along with hundreds of others, can concentrate nitrates and be a potential cause of "silo-fillers disease" or possibly dangerous when ensiled and fed to livestock. However, the plant is seldom, if ever, found in sufficient abundance to cause these problems. This plant is sometimes grown as an ornamental. Many Cleomes in the Tropics are used as foods, medicines, and dyes, but I found no mention of economic uses for Rocky Mountain beeplant.
This species is a member of the caper family (Capparaceae), named after similarly pungent capers, the edible flower-buds of a Mediterranean plant, Capparis spinosa. This is a relatively small family of about 900 species, mostly tropical, that contains many trees and shrubs. The generic name Cleome is an ancient Latin name of some member of the mustard family. The specific epithet serrulata means "finely toothed" in botanical Latin. Rocky Mountain beeplant was described for science by the eminent German botanist Frederick Traugott Pursh (1774-1820) in his monumental Flora Americae Septentrionalis of 1814. Pursh was the first to publish on the many new plants collected by Lewis and Clark.