WHITE SNAKEROOT, Eupatorium rugosum Houtt. 1, upper part of plant; 2, root; 3, flower head; 4, single flower; 5, seed. Perennial, spreading by seeds and short rhizomes. Roots much branched and fibrous. Stem 1 to 3 feet (30 to 90 cm) tall, smooth, and branched near top. Leaves opposite, elliptical, thin, smooth, with toothed edges and slender petioles. Flower heads small, of white disk flowers only. Seed black, angular, about 1/8 inch (3 mm) long, with a tuft of white hairs. Found in hardwood timber areas, woodland, pastures, and waste places. It grows only in shaded areas. Contains a cumulative poison that causes the disease known as "trembles" in cattle and horses. Dairy products from animals that have eaten the plant are poisonous to man, causing "milk sickness," one of the serious scourges of pioneers in the region.