Published August, 2010

Common name: Tall ironweed
Scientific name: Vernonia gigantea (Walt.) Trel.

Life Cycle: Warm season perennial
Origin: North America
Poisonous: No

Tall ironweed is distributed widely across the eastern half of the United States and is found in low damp areas of pastures and roadsides. This tall, upright plant can approach 10 feet under optimum growing conditions but more commonly grows to about 5 feet. Tall ironweed is rarely eaten by animals. The leaves are rough and sharply toothed, with small downy hairs on the underside of the leaf. The leaves alternate along the stem and are 2-10 inches long. Tall ironweed reproduces from seeds and buds on the crown of a deep, vigorous taproot. Flowers are reddish to deep purple in color.

Tall ironweed control is possible when herbicides are applied to plants less than 12-15 inches tall that have not been mowed. Effective control also is obtained after plants are mowed and when regrowth is treated with herbicide. Late May through August is the preferred time for herbicide application. Mowing is an effective treatment to prevent seed production. Consult your local Cooperative Extension Service personnel for herbicidal control in your area.

William W. Witt, PhD, a researcher in Plant and Soil Sciences, provided this information.