Western poison ivy is small deciduous bush, low and creeping or erect one, up to 2 m high. It has pilose annual shoots. Leaves are trifoliolate, glossily, 5 to 15 cm long. They turn brown, red, or orange in autumn. Flowers are inconspicuous, greenish, in small erect panicles. Western poison ivy blossoms from April to July. Fruit is white, yellowish, or greenish drupe. It grows in wooded areas, mostly near streams. It ranges almost the whole North America except Alaska, northern and northeast Canada, California, and the southeast USA.
Western poison ivy is one of the most feared plants of the North America. All parts of the plant have channels containing milky juice which turns black on air. The juice contains volatile phenolic derivate urushiol which causes acute allergic reactions. About 12 hours after touch, stain, or carry by insects, hard itchily and acute skin irritation appears. It cures uneasily. If a larger area is struck, the irritation can endanger life. Western poison ivy caused big problems to Cheyennes too so they used least four medicinal plants to relieve from mentioned allergic reactions — soapweed yucca(Yucca glauca), upright prairie coneflower (Rudbeckia columnaris), prairie milkvetch (Astragalus nitidus), and alpine alumroot (Heuchera ovalifolia).
