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Plant taxonomy classifies common ragweed as Ambrosia artemisiifolia. Although giant ragweed (Ambrosia trifida) is a very different-looking plant from common ragweed, both are responsible for hay fever.
Ragweeds are weeds that grow throughout the United States. They are most common in the Eastern states and the Midwest. A plant lives only one season, but that plant produces up to 1 billion pollen grains. Pollen-producing and seed-producing flowers grow on the same plant but are separate organs. After midsummer, as nights grow longer, ragweed flowers mature and release pollen. Warmth, humidity and breezes after sunrise help the release. The pollen must then travel by air to another plant to fertilize the seed for growth the coming year.
Ragweed plants usually grow in rural areas. These annual plants are easily overgrown by turf grasses and other perennial plants that come up from established stems every year. But where the soil is disturbed by streams of water, cultivation or chemical effects such as winter salting of roads, ragweed will grow. It is often found along roadsides and river banks, in vacant lots and fields. Seeds in the soil even after many decades will grow when conditions are right. |
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