Chicago gardeners, the symptoms of hay fever—watery eyes, inflammation of your respiratory tract and runny nose—have little to do with hay. Allergic rhinitis, a better name for hay fever, is triggered by weed pollen in the fall. In spring, flowering trees cause these allergic reactions; in summer, field grasses are to blame. In autumn, the pollen of the ragweed is most often the cause; even honeybees avoid ragweed.
Ragweed belongs to the genus Ambrosia of the family ASTERACEAE. There are 41 species of this noxious weed. It’s native throughout the Northern Hemisphere and in South America. Varieties can be annuals or perennials. Some varieties are herbaceous plants, subshrubs or shrubs. Common ragweed can grow to more than seven feet tall. Great ragweed can grow to 13 feet tall.
The plant produces grayish, silver green leaves. It grows separate male flowers colored greenish-yellow. The female flowers, pollenated by the wind, are colored whitish-green and produce a prickly burr (fruit). Each burr contains only one arrow-shaped seed, carried by birds and other animals. Each ragweed plant produces nearly a billion grains of pollen, wind-blown over vast areas and midair for days. Ragweed adapts well in prairies and beside rivers, vacant lots and abandoned property. They prefer sunny areas and sandy soil.
Ragweed is difficult to control but not impossible. Consistent mowing works. Pulling out the plants in the spring before they mature helps. Chemical spraying with herbicides kills the plants, but it may kill other, desirable vegetation as well.
Goldenrod, a beautiful, medicinal plant, shouldn’t be confused with ragweed. It belongs to the aster family, but it’s part of a different genus, Solidago. Goldenrod pollen rarely causes allergies, and the plants are pollenated locally by insects.
Live long and well—garden.
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