Common ragweed

August 25, 2015

Ambrosia artemisiifolia

Life cycle

Erect, branching summer annual.

common ragweed seedling
Common ragweed seedling.

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.

giant ragweed seedling giant ragweed new leaf
Giant ragweed seedling (left) and leaf (right).

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. 

Western ragweed seedling Western ragweed leaf
Western ragweed root sprout (left) and leaf (right).

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