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.
Erect, branching summer annual.
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.
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.
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.