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Weed of the Month: Common Ragweed

Common ragweed is distributed widely across the United States and grows in pastures and among cultivated crops.

Photo: University of Kentucky's College of Agriculture, Food, and Environment

Common name: Common ragweed
Scientific name: Ambrosia artemisiifolia L.

Life Cycle: Warm season annual
Origin: United States
Poisonous: No

Common ragweed is distributed widely across the United States and grows in pastures and among cultivated crops. Pasture infestations are usually more of a problem during periods of drought or when overgrazing occurs. Leaves alternate between the upper and lower portions of the stem, which can be smooth or hairy and is usually branched. Mature plants can grow to 3 to 5 feet, depending on the area of growth. Common ragweed has small female flowers in the leaf axils. Showier male flowers grow at the top of the plant.

Mature plants can grow to 3 to 5 feet, depending on the area of growth.

Photo: University of Kentucky's College of Agriculture, Food, and Environment

Common ragweed control is relatively easy with herbicides, if property managers apply it to unmowed plants less than 12 inches tall. Treatment time is normally between May and July. Mowing is not very effective, as it tends to remove the top of the ragweed plant and lateral branching occurs on the remaining plant. This “regrowth” is much more difficult to control with herbicides. Hand weeding is effective and should be done before seed production. Consult your local Cooperative Extension Service personnel for herbicidal control recommendations in your area.

William W. Witt, PhD, professor emeritus in the department of plant and soil sciences at the University of Kentucky, provided this information.


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