Asclepias cordifolia is a species of milkweed commonly called Heart-leaf milkweed or Purple milkweed (not to be confused with Asclepias purpurascens, also commonly called Purple milkweed). It is native to the western United States (California, Nevada, Oregon), growing between 50-2000 meter elevation in the northern Sierra and Cascade ranges. Heart-leaf milkweed was valued by the Native American Miwok for its stems, which they dried and processed into cordage (string and rope). Monarch butterfly caterpillars eat the Heart-leaf milkweed leaves, which contain alkaloids that cause the butterfly to be unpalatable to predators. The species name, cordifolia (Latin for 'heart-leaved'), refers to the heart-shaped leaves, while the genus name honors the Greek physician Asclepius. Heart-leaf milkweed is a perennial that grows to a height of 0.3-0.6 meter, with dark red-purple flowers whose hoods are slightly elevated above the base of the corolla. The flower structure is unusual-it has five stamens fused into a column, with five circular attachments called 'hoods', and an anther head surrounding the large stigma at the flower's center. The fruit (photo at left) is a follicle with many flat seeds that have silky hairs which disperse easily in the wind. The large opposite leaves are heart-shaped, or heart-shaped. The plant grows in open or shaded woodland, often on rocky slopes and in mixed coniferous forest.