Lupinus formosus, the summer lupine or western lupine, is a species of flowering plant in the legume family, Fabaceae. It is native to California and Oregon in the United States. Lupinus formosus has been cited as a poisonous plant. Although it is not endangered it faces eradication in some areas at the hands of cattle farmers as it has been implicated in crooked calf disease. This lupine, along with five others, is poisonous from the time it starts growth in the spring until the seed pods shatter in late summer or early fall. However, the younger the plant the more toxic it is.