Lupinus caudatus is a widespread species of wildflower in genus Lupinus from western North America known by the common names tailcup lupin and spurred lupin. It is distinctive for the short spur on its purple-blue flowers, for which it is named. Because of its wide distribution and toxicity it commonly causes poisonings of susceptible livestock such as horses, cattle, and sheep, though it is eaten without harm by wild herbivores like deer and elk. It is generally found from the Coastal Ranges and Sierra Nevada Mountains in the west to the Rocky Mountains in the east.

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