Weed of the Month: Common Ragweed

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

Common ragweed control is relatively easy: apply herbicides to plants less than 12 inches tall that have not been mowed. Treatment time is normally between May and July. Mowing is not very effective. Mowing heights in horse pastures tend 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 information on herbicidal control in your area.

Common ragweed

Common ragweed

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

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

William W. Witt, PhD, a researcher in Plant and Soil Sciences at the University of Kentucky, provided this information.


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Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.