Nature Bulletin No. 160 September 13, 1964
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation
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
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
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
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.
To return to the Nature Bulletins Click Here!
Update: June 2012