Both great and common ragweeds are shedding pollen, but we are approaching the peak of the ragweed pollen season, which will end on a frosty day.
Great ragweed is a tall plant, 3 to 10 feet high, with rough stems and broad three-lobed leaves. The tiny nodding green flowers (which sprout from the plant's long spikes) shed large quantities of pollen. People who are sensitive to this pollen and come in contact with it develop symptoms of hay fever allergy such as watery eyes, sneezing, stuffy nose, headache and fatigue.
The more numerous plants of common ragweed have finer, more dissected leaves, and the plants grow only 1 foot to 4 feet tall. As with the great ragweed, its windblown pollen is released from small green flowers. Together, these two ragweed species cause more hay fever than all other plants put together.
Nevertheless, the native ragweeds play a positive role in nature. As pioneer plants, they invade disturbed soil, helping greatly to cut down on erosion. Look for these plants on flood plains, along roadsides, in fields and on vacant lots.
Being annuals, they are replaced in two to four years by perennial plants such as asters. Ragweeds also provide valuable winter food for such ground-feeding birds as pheasants, juncos and redpolls. Their seeds are rich in oil, and the seed production per plant is enormous.
Jim Gilbert's Nature Notes are heard on WCCO Radio Sundays at 7:15 a.m. His observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He taught and worked as a naturalist for 50 years.
