Northern Prairie Wildlife Research Center
Approximately the western two-thirds of North Dakota is home to slender locoweed. This species is restricted to the northern Great Plains and Pacific Northwest at elevations under 10,000 ft.
Slender locoweed is perennial from a heavy taproot topped by a knobby underground crown called a caudex. North Dakota specimens are usually about 8-10 inches tall and silky-hairy. Leaves about two-thirds as tall as the plant arise mostly from the base and are pinnate, like two combs held back-to-back. Each leaf has about 11-33 oblong leaflets. About 10-20 whitish, yellowish (usually), or bluish flowers, each about 1/2 inch long, form dense clusters on scapes that overtop the leaves. Fruits are pods (legumes) about 1/4 inch long that contain smooth, dark brown seeds.
Look for slender locoweed beginning in late May on hillsides in heavily or moderately grazed native prairie. Cattle seem to avoid the plant, even though it is not listed among the locoweeds known to poison livestock.
The locoweeds are members of the bean family (Fabaceae), which contains about 10,000 species of herbs, shrubs, and trees, many of which are of great economic importance. Fab means "bean" in Latin. The generic name was compounded from the Greek oxys, "sharp," and tropis, "keel," in reference to the pointed tip on the two lower flower petals. The specific name campestris means "pertaining to the plains" in botanical Latin. After its recognition as a new species by the Swedish father of modern botany, Linnaeus, slender locoweed was first scientifically described in 1834 by the Swiss-French botanist Augustin Pyramus deCandolle (1778-1841). Three generations of his family subsequently worked on a worldwide flora, the Prodromus, which was never completed.