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.
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.
|Seedling: 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.
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.|
|Roots: Shallow taproot.
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.
|Identifying Characteristics: Cotyledons with purple underside. Fruit an achene resembling a queen's crown.|