Giant ragweed

Ambrosia trifida

Asteraceae (Sunflower Family)


Giant ragweed is an annual that frequently exceeds 10 feet tall in moist locations; in drier areas it may mature at a smaller height. Its stems and leaves are rough.

The leaves have long petioles, are opposite each other, and are attached to a single center stem. They usually are divided into three lobes but can have five or none. The flowers are either male or female and are located in clusters at the top of the plant; they often exceed 6 inches in length. The pollen spread shortly after flowering in the fall causing many people to have hay fever problems. The seeds are .25 inches long and have four or five terminal spikes on each.


Giant ragweed is found in moist areas near roadsides and disturbed sites.