Plant Allergies

6 June 2006

Virginia Cooperative Extension, Charlottesville/Albemarle County Office
460 Stagecoach Road, Charlottesville, Virginia 22902
phone: 434.872.4580   fax: 434.872.4578

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Have you ever had a beautiful day spoiled by public displays of pollination? We humans sometimes have a vicarious reaction to this sort of behavior but it is not always because we are thinking about it. Often we are the innocent sneezing and sniffling victims of pollen or spore distribution via a nice spring breeze.

Plants produce pollen or spores in order to reproduce. Some plants self-fertilize and others need to cross-pollinate. In many cases pollen or spores need to move from one place to another. Insects are pollinators for some plants and others require the help of wind. It is these wind pollinators that cause us so much concern.

Allergic reactions are caused by an overactive immune system response to a foreign substance such as pollen, dust, or fungi. When this reaction affects the eyes or nose typical symptoms include sneezing, a runny nose, and itchy watery eyes. When an inflammation affects the bronchial tubes, it can result in asthma. Typical symptoms include wheezing and shortness of breath.

The worst pollen allergens are typically from weeds, grasses, and certain trees. Because these plants are wind-pollinated, they produce a lot of powdery, easily inhaled pollen that can trigger allergic responses. Insect pollinated plants, such as flowers and vegetables, have pollen that is large and sticky, which generally does not cause as many problems. However, individuals who are repeatedly exposed to these plants may develop allergies to them as well.

Problem Plants

The most typical allergenic plants include weeds such as ragweed, pigweed, and lambs quarters. Troublesome grasses include timothy, Kentucky bluegrass, Johnson grass, Bermuda grass, redtop, and orchard grass. Large shade trees such as oaks, elms, maples, pecans, mulberries, and cottonwoods can also cause problems. Most individuals are allergic to only one or two trees. Because these trees pollinate a few weeks each year, allergic reactions can be avoided by staying indoors, wearing a protective mask, or taking medication during the weeks that they are pollinating. Some individuals may also be allergic to trees in the juniper, cypress, and sequoia families including the Eastern Red Cedar seen on many Virginia roadsides. These trees pollinate in the winter months of January, February, and early March.

Besides weeds, trees, and grasses, fungi can also cause allergic reactions. They release spores into the atmosphere all year long in areas where there is abundant organic matter, moisture, and warmth. Leaf piles and compost areas can produce many fungi. The results of working near a compost pile could be even more serious than asthma or allergic rhinitis, as some fungi can colonize in asthmatic bronchial tubes, leading to more serious conditions.

Prevention

If you experience allergic reactions while working outdoors, consult with your local doctor or allergist to determine which plants are responsible and when they pollinate. You can then formulate your own personalized calendar indicating your best and worst times to be outdoors.

If you do go outside, there are several ways to minimize your exposure to pollen. These include wearing gloves, a long sleeved shirt, hat, and sunglasses or goggles. A pollen mask may also be necessary. After working outside, take a shower, thoroughly wash hair, and change clothes.

Weather conditions can affect the abundance of allergens in the air. Wind pollinated plants will not release pollen when it is raining, and instead are more dangerous on hot, windy days. Mold and fungi spores, on the other hand, are more abundant during wet weather. Save gardening for days when your allergen counts are low.

Individuals with allergies should avoid certain garden chores that aggravate their symptoms, such as working in the compost pile, working with mulch or straw, raking, using power blowers, or mowing lawns. Mowing grass can cause grass particles, pollen, and mold to become airborne.

You can minimize your exposure by planting trees, grasses, or shrubs that do not cause allergies. Choose plants that are insect-pollinated when possible. Keep grass trimmed so it does not flower. If allergies prevent you from mowing, it may be wise to invest in a yard care service or reduce your lawn area by adding flower beds or ground covers.

Certain species of the Compositae or Asteraceae plant family, such as daisies, mums, marigolds, sunflowers, and dahlias, may be cross-reactive for individuals with ragweed sensitivity. This plant family has close to 20,000 known species, including many herbs, and some shrubs, trees, and vines.

In your own landscape you can help yourself by learning to identify the most common weeds and eliminating them from your landscape or garden early, before they reach maturity and flower.

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For more information about these and other landscape gardening topics contact your local Virginia Cooperative Extension office. The local Virginia Cooperative Extension office numbers are Albemarle 872-4580, Fluvanna 591-1950, Greene 985-5236, Louisa 540-967-3422, and Nelson 263-4035.