SKELETONLEAF BURSAGE, Ambrosia tomentosa Nutt. 1, top of plant; 2, root system and young plant; 3, male flowers; 4, seed. Perennial, reproducing by seeds and deep creeping rhizomes. Stems bushy, branched, usually 1 to 2 feet (30 to 60 cm) tall. Leaves alternate, divided into narrow lobes, hairy on underside, 2 to 5 inches (5 to 12.5 cm) long. Flowers small, male and female borne separately but on the same plant. Male flowers in small drooping heads along tips of branches; female in axils of upper leaves. Burs surrounding female flowers bear 1 to 3 seeds, have sharp spines when mature. Found in moist cultivated fields, waste places, pastures, and irrigated areas, especially if poorly drained.

WOOLLYLEAF BURSAGE, Ambrosia grayi (A., Nels.) Shinners. A species closely related to the above. Leaves covered with short woolly hairs on both surfaces, terminal lobe quite large. Bur has curved rather than straight spines.