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The Homeowners Column
Identifying irritating ragweed
State Master Gardener Coordinator
A snort, a sneeze, followed by two sniffles. Ahhh it's the call of the allergy sufferer. With the tell-tale symptoms of sneezing, runny nose and itchy, watery eyes an estimated 50 million people suffer each year from allergies. Although people can be allergic to many different things (pet dander, work, mold, and fragrances), flower pollen is a common allergen.
You may remember (as you dust off a few brain cells) that pollen is the male genetic contribution in pollination and sexual reproduction in flowering plants. Basically pollen has to get to the female parts of the flower by some method in order for seeds to be produceds. Since planes, trains and automobiles are not an option; plants often use pollinator insects or the wind to move the pollen around.
As fall approaches goldenrod shows off its bright yellow flowers, so many people blame it for their summer allergies. In reality the disregarded ragweed near the goldenrod is the likely culprit. Goldenrod pollen is not physically adapted to be an extreme allergen. Its showy yellow flowers are designed to attract insect pollinators; therefore, the pollen is heavy and sticky to easily cling to the insects for a ride to the next flower. Heavy sticky pollen does not blow well in the wind or up your nose. However ragweed has homely tiny green flowers and relies on wind pollination. Ragweed overwhelms the air with lightweight pollen in the hopes it will land on another ragweed flower. Each ragweed plant can produce an estimated one billion pollen grains. Just a few plants can create an invisible cloud of polluting pollen.
In our area two ragweed species are
the most abundant: common ragweed (Ambrosia
artemisiifolia) and giant ragweed (Ambrosia
trifida). Both are native annuals that reproduce from seeds. Common ragweed
is indeed common along roadsides, cultivated fields, vacant lots and pastures.
It grows one to four feet tall with densely hairy stems and deeply lobed (almost
ferny) leaves. Common ragweed grows well in gravelly areas along roads where it
thrives under abuses that would knock out most plants.
Giant ragweed is a larger version at 13 to 15 feet tall. Its coarse, rough stems hold large, slightly hairy leaves that grow almost a foot long with three or sometimes five pointed lobes. Giant ragweed can be common in cultivated fields, fence rows, roadsides and unmown construction sites. Some populations of giant ragweed survive even after herbicide applications.
Ragweeds are very competitive plants that succeed in areas where few other plants will live. As first invader plants they love disturbed soil. We humans are very adept at disturbing the soil through tilling and construction. Ragweed seeds can survive in the soil for over thirty years, just waiting for proper conditions for germination.
We may be hard pressed to find a good use for ragweed; however the fruits are a highly nutritional food for songbirds and other wildlife. Prehistoric Native Americans reportedly collected the seeds for food and may have actually cultivated giant ragweed.
Since ragweed pollen is a common allergen doing our part to control plants helps everyone. Ragweeds are annuals; therefore their control hinges on eliminating seed production. Cut stems or cultivate flowering ragweed so they do not "go to seed" to help reduce their population. Next season mulch the area and remove plants in May or June before flowering.
Plants shed pollen at different times of the year, so a look at the calendar and which plants bear wind pollinated flowers during that period may help to narrow down the culprits. Late spring allergies may be from tree pollen, while summer sniffles may be from grass pollen. Unfortunately with climate change allergies from pollen appear to be starting earlier and lasting longer. People's sensitivity to certain plants can vary widely, so always discuss your allergies with your health care professional.