Common Ragweed

Ambrosia artemisiifolia

Weed Description
Summer annual, 0.2-2.5 m tall, found throughout the United States, producing abundant pollen that is a primary cause of hay fever.

Seedlings
Stems below cotyledons (hypocotyls) are green, usually spotted with purple. Cotyledons are roundish to oblong, purple underneath. Young leaves opposite, becoming alternate with age, dense pubescence over entire leaf surface.

Leaves
Leaves are 4 to 10 cm long, egg-shaped in outline and once or twice compound (pinnatifid). Leaves hairy on upper surface and margin, densely appressed on lower surface.

Stems
Erect, branched, with long, rough hairs.

Flowers
Flower heads small (2-4 mm broad), green, and arranged in slender inverted racemes at the ends of branches. Male and female flowers are in separate heads on the same plant, the male flowers, usually drooping, are at the top of the plant, while the female flowers are in the upper leaves and bases of leaves.

Fruit
Woody achene, yellowish- to reddish-brown, 3-4 mm long and 1.8-2.5 mm wide, 1-2 mm central protuberance surrounded by 4-7 shorter projections. Resembles a crown.

Roots
Shallow taproot.

Office of Programs

University of Missouri

Common Ragweed

Ambrosia artemisiifolia