Scouting for weeds: Common ragweed

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

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.

Stem

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. (See pages 62-63.)

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.

Editor’s note: This and more weed identification information is available in the field guide An IPM Pocket Guide for Weed Identification in Field Crops. To order, call 517-353-6740.

leaf. Seedling
Photo 1. Common ragweed leaf.  Photo 2. Common ragweed
seedling.

flowering branch
Photo 3. Common ragweed
flowering branch.

root sprout Leaf
Photo 4. Western ragweed root sprout. Photo 5. Western
ragweed leaf.

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