Types of Ragweed

Identification and Size

• Ragweed plants have hairy green stems and divided leaves that are irregularly lobed. Their green or yellow flowers grow in terminal spikes. The different types of ragweed range in size from common ragweed, which grows from almost a foot to nearly 5 feet high, to the giant ragweed, which reaches up to about 13 to 16 feet tall, according to the University of Tulsa.

Common Ragweed

• Common ragweed is a summer annual plant that grows throughout the United States. This ragweed has long, compound, elliptical leaves. The upper surface of the leaves is hairy. The plant's hairy stems grow upright and are branched. Common ragweed has small flower heads that grow on the tips of branches. It produces a woody yellow or brown fruit and has shallow taproots. The pollen released from common ragweed is the main cause of hay fever.

Western Ragweed

• The leaves and flowers of western ragweed are similar to those of common ragweed, although western ragweed plants have rougher and thicker leaves and stems. The western ragweed has branched stems and generally grows ordinary-looking male flowers on the upper portion of its flowering stalks. This weed is a creeping perennial that is commonly found along roadsides and in pastures and vacant lots.

Giant Ragweed

• Giant ragweed, which is an annual plant, has green stems with white hairs. This ragweed has opposite leaves that grow up to 12 inches long and 8 inches wide. Its small yellowish-green flowers grow in clusters and lack petals and sepals. Giant ragweed produces fine pollen that's carried by the wind, usually during the late spring or early autumn. The plant's large seeds can stay living in soil for several years.

Warning

• Giant ragweed is extremely aggressive and is mostly hard to control in broadleaf crops such as soybeans. Because it can surface from deep soil levels, it's able to escape many herbicides that are applied to soil. The thickest populations are found in tilled soil. Giant ragweed can travel far on windy, dry days and is prone to clump when the humidity is more than 70 percent.