WESTERN RAGWEED, Ambrosia
psilostachya DC. 1, male flowers on spike; 2, female
flowers; 3, seed; 4, entire plant. Perennial, reproducing
by rootstocks and seeds. Stem erect, normally less than 20 inches
(50 cm) tall, hairy, bushy, branched above, often growing in dense patches.
Leaves with short petioles, alternate or opposite, ovate-lanceolate,
with very deep lobes, sometimes compound, rough. Flowers of two
kinds. Male flowers in clusters on ends of stems and branches; female flowers
few, without petals, in axils of upper leaves. Seed about 1/8 inch
(3 mm) long, with a woody hull that has a pointed tip surrounded by short
spines. Found in prairies, plains, and uncultivated areas. The pollen
is a hazard to hay fever sufferers. Also known as perennial ragweed.