: any of several leguminous plants (genera Astragalus and Oxytropis) of western North America that cause locoism in livestock
Any of several species of poisonous plants of the genera Astragalus and Oxytropis, in the pea family (seelegume), native to the prairies of north-central and western North America. These low-growing plants (up to 1.5 ft [45 cm] high) have variably hairy, fernlike leaves and spikes of pealike flowers. They pose a danger to grazing animals because they contain a toxin that affects muscle control, producing frenzied behaviour, impaired vision, and sometimes death. Because they taste bad, livestock usually eat them only when other forage is scarce. Decaying locoweeds release toxins into the soil that are sometimes absorbed by otherwise harmless forage crops.