Ragweed Households

Of the ragweed family there seems to be four house-holds containing weeds that produce hay fever. In scientific plant language each household is called a genus and the members of the household are called species. A group of households (genera) comprise a family. The four important ragweed households are Ambrosia, Gaertner, Iva and Xanthium. These sound respectable, but they really aren’t. They are only dressed up in their latin names which we have included for want of a common name.


The most important ragweed group is the Ambrosia. This household includes dwarf ragweed, giant ragweed, western ragweed and southern ragweed. Of this group, the first two named account for 8o to 90 percent of the fall hay fever in the northeastern part of the United States. They are the Mutt and Jeff of the family. They are variously known as dwarf and giant, low and high, or short and tall ragweed. Like the other ragweeds they are similar to each other in their potency to cause hay fever but are somewhat different in appearance.

Short Ragweed. This notorious weed is the best known and most widely distributed of the ragweeds. For this reason it is often called common ragweed. The plant is easy to recognize once you have become familiar with its fern-like leaves and clusters of tiny, green, bud-like flowers arranged in spikes along the top and side branches. The green flower clusters which form the spikes contain only the male stamens for producing pollens. They can be seen completely covered with yellow pollen late in August and September when they are pollinating. The female flowers are inconspicuously located at the points where the leaf stems arise from the central stalk.

The stems and spikes often grow out in a circular and candellabra-like form. The plant averages about one and one half feet in height but grows to four and five feet under favorable conditions.

Short ragweed is abundant in the roadsides and fields of Massachusetts, Connecticut, Vermont, New York, Rhode Island and Pennsylvania. It just chokes up the agricultural fields after harvest time in Mississippi, Missouri, Iowa, Illinois and Indiana. As a matter of fact it is an important cause of hay fever clear across the United States, from the east up to the west coast states.

Pollination begins during the second week in August but you may not experience your symptoms until the second or third week. This depends upon where you are living and your degree of sensitivity during any one sea-son.

Giant Ragweed. This taller member of the ragweeds is the best pollen producer of the entire family but its pollen is not as strong as that of short ragweed. It needs moist and richer soil than the other ragweeds. Its usual height is five to six feet. In areas near river bottoms where the ground is damp and favorable it grows to fifteen feet. Like short ragweed it is spread over a large area of the United States, but unlike its short brother it is scarce in the New England states.

Tall ragweed can be unmistakably distinguished by its long three and five lobed leaves, its height, and its long spikes of green pollen bearing clusters of flowers. This species begins to pollinate about the first week in August, which is a little earlier than the short ragweed.

Western Ragweed. As its name implies, this member of the family favors the west. It looks very much like short ragweed except that it is fuller, more bunchy and slightly taller. It is a perennial, that is, it does not die from year to year. Western ragweed grows abundantly in the Mississippi valley and in the southern parts of California, New Mexico and Texas. Pollination begins at the end of July and continues through September.

Southern Ragweed. This member is the least common of the ragweeds. But just to make sure that the country was thoroughly covered this member grows sparsely in the central southern states of Texas, Louisiana, Missouri, Oklahoma and Kansas.


The remaining plants of the ragweed family that are important to hay fever, are members of the other three households. A so-called false ragweed is found in the states from Kansas southward and westward to the coast but skips the Rocky Mountain area. Its pollen is potent to a ragweed sufferer and is spread from July to October.

A ragweed that doesn’t bear the name is the marsh elder which grows profusely in some areas of Kansas, Missouri, Illinois, Arkansas and Tennessee. One member of this species, burweed marsh elder, is common to certain sections of the Rocky Mountains, which regions are other-wise relatively free of the common dwarf and giant ragweeds.

A more important ragweed relative is cocklebur. It does not look like the ragweeds but gives off pollens that are harmful to hay fever sufferers.