Common ragweed – Ambrosia artemisiifolia

Common ragweed leaf

Common ragweed leaf

Common ragweed flowering branch

Common ragweed flowering branch

Common ragweed seedling

Common ragweed seedling

Common ragweed

Ambrosia artemisiifolia L.
Asteraceae (Aster family)

Life cycle
Erect, branching summer annual.

Leaves
Cotyledons are thick and oval to spatula-shaped. Leaves are fernlike, once or twice compound and usually hairy. Upper leaves are alternate; lower leaves may be opposite or alternate with distinct petioles.

Stems
Usually hairy, erect and branched up to 6 feet tall.

Flowers and fruit
Flowers are generally inconspicuous, found on terminal branches. They produce prolific amounts of pollen. The seed is enclosed in a single-seeded, woody fruit with several spikes resembling a crown.

Reproduction
Seeds.

Similar weeds
Giant ragweed (A. trifida L.)
Differs by having cotyledons three to four times larger; three- to five-lobed leaves opposite in arrangement; and a height that may reach 15 feet.
Western ragweed (A. psilostachya DC.)
Differs by having a perennial nature with prolific creeping roots, densely hairy leaves and a height typically not above 4 feet.