Ragweed

August Weed - Common RagweedMary Anna Anderson

Mary Anna Anderson of University of Nebraska Extension, supplies us with information on weeds to watch for each month. Here is a weed of special concern to those with allergies.

Weed: Ambrosia artemisifolia also is called common ragweed, annual ragweed, Roman wormweed, wild tansy, and hogweed. It is in the sunflower (Asteraceae) family.

Description: An annual weed that usually grows from 1 to 2 feet, but can grow up to 4 feet tall. It has hairy leaves that are dissected, and compound, giving the plant an appearance of a fern. The leaves are opposite on the lower stem, and alternate on upper part of the stem. It has a shallow taproot.

Where: Grows in most soils but does especially well in heavy, moist soils. Ragweed is most commonly found in disturbed areas, including corn and soybean fields. It also can be found in marshes, beaches, roadsides, gardens, and vacant lots.

Common Ragweed, young plantPropagation: Common ragweed is an annual plant that grows from seed. Its seed requires winter chilling in order to germinate. Ragweed has separate male and female flowers on a plant. The male flowers are spikes on the top of the plant. The female flowers are inconspicuous and grow singly or in clusters in the axils of the leaves. The flowers are wind pollinated. The seeds are spread by water, birds and burrowing animals. A single plant can produce 30,000 to 60,000 seeds. It does not survive more than a couple of years in the top two inches of soil, but seeds that are buried can survive 39 years in the soil.

Poisoning: It can cause nausea and sore mouths in livestock that feed on it.

Historical: Common ragweed is a native of North America, and has now spread to Europe and South America.

What: Ragweed absorbs trace nutrients very efficiently. It will take in more boron, copper, magnesium, zinc, tin, gallium, potassium, calcium than corn. A large common ragweed population in the farm field can cause a nutrient deficiency. The plant can tolerate mowing, trampling, and grazing, which contributes to its difficulty to control.

Pros: Insects, such as grasshoppers, eat the leaves. Eastern cottontails feed on the plant. The seeds are important food for bobwhite quail, meadow voles, mourning doves, American goldfinches, and red-bellied woodpeckers.

Ragweed's medicinal properties include astringent, antiseptic properties. Healers and herbalists prepare remedies from the roots and leaves. Some people crush the leaves and apply the juice to soothe insect bites and poison ivy rashes. Supposedly, Native Americans prepared a poultice from crushed leaves to relieve swelling and prevent infection, and used it as a remedy for nausea and also as a laxative.
Ragweed photo by W. Justice, USDA Plant Database
Cons: Along with giant ragweed (Ambrosia trifida), its pollen is a major cause of hay fever. Because it blooms around the same time, goldenrod (which is insect pollinated, and not wind pollinated) often gets the blame for allergies. Each ragweed plant may contain a billion pollen grains and be carried 400 miles by the wind...aaachoo! It is estimated that 1 million tons of ragweed pollen are produced each year in North America.

The lower photo to the right was taken by William Justice, and was found in the USDA-NRCS Plant Database. This is an excellent source of information and images, including photos and line drawings, of plants found throughout the US.