Forest Preserve District of Cook County, Illinois
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Ragweeds
Nature Bulletin No. 160   September 13, 1964
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

RAGWEEDS
Late summer and early autumn is "hay fever time." This is the season dreaded by thousands of people who are allergic to the wind-borne pollen of the ragweeds which is shed then. The ragweeds are more abundant and cover more acres in this region than any other weeds.

Of the three kinds in the Chicago area, the two most widespread are the plants growing only from seeds and dying each winter. They thrive abundantly wherever the soil has been disturbed recently. Their seeds can survive for many years in the ground -- waiting only for the soil to be stirred for them to germinate and grow. Most of our troublesome weeds came from the Old World but the ragweeds are native Americans.

The third species, the Western Ragweed, is a perennial growing both from seeds and rootstocks that live over the winter. Less common and less well known. It resembles the common ragweed In appearance.

The giant ragweed, commonly reaching 10 feet in height and occasionally 20 feet, is our tallest weed. The leaves are large and deeply lobed, usually into three parts. It prefers fertile dark soils, growing tallest and densest on the rich moist floodplains of streams. Bird watchers come here to see small birds In winter and youngsters plan Indian using the long stiff stems for spears.

The common ragweed is smaller, seldom taller than 5 feet. It is easily the most common weed on roadsides, waste places and, especially, in stubble fields after the wheat or oats have been harvested. Both this and the western ragweed have leaves divided and subdivided into many parts.

The male flowers on the tips of the branches launch millions of light dry pollen grains into the air. A west wind can even carry them across Lake Michigan. Few people have a good word to say for these unattractive plants unless they know about their food value to bird life. The seeds are rich in oil and the seed production per plant is enormous. Some of the seeds remain on the plant into winter where they can be found when other foods are covered by snow. They are a main item in the diet of game birds, especially the bobwhite quail, and for many of our best-loved songbirds such as the goldfinch, song sparrow, white-throated sparrow, and the junco or snowbird.


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