COMMON RAGWEED, Ambrosia artemisiifolia L. 1, plant; 2, seed; 3, distribution. Annual, shallow-rooted. Stems rough, hairy, erect, branched, 1 to 4 feet (0.3 to 1.2 m) tall. Leaves nearly smooth, deeply cut into a number of lobes, mostly alternate. Flowers of two kinds; male pollen-producing flowers in small inverted clusters at tips of branches; seed-producing flowers fewer, borne at the bases of leaves and in forks of upper branches. Seed about 1/8 inch (3 mm) long, enclosed in woody hull, light brown, top-shaped, pointed, bearing several longitudinal ridges ending in short, spiny projections. Found in old pastures, wasteland, roadsides, stubblefields, and cultivated land. Produces pollen abundantly and is a hazard to hay fever sufferers.

 LANCELEAF RAGWEED, Ambrosia bidentata Michx. 4, portion of stem showing toothed leaves and flowers; 5, seed; 6, distribution. Similar to the above. Leaves abundant, lanceolate, partly clasping the stem, hairy, bearing 1, 2, or more large sharp teeth on each side of a broad base. Seeds 4-angled with 4 sharp spines.