Birds, bees, flowers and trees are the recipe for spring and summer allergies, especially for devoted gardeners. Converting a landscape into silk flowers, gravel beds and garden gnomes or plastic flamingos will not lessen gardener’s grief. Perhaps changing some gardening practices, or some plants, may be all that is needed.

Garden plants are pollinated by insects, wind or self-pollination. Biotic pollination requires living vertebrate or insects, such as honeybees or hummingbirds. Biotic pollinated plants have male and female parts existing in the same flower. Pollen is tiny, egg-shaped male reproductive cells of the flower. Insect- or vertebrate-pollinated plants tend to have heavy sticky pollen so it will stick well to bees and other insects as they travel from flower to flower.

Attractive, brightly colored flowers pollinated only by insects rarely cause allergies unless planted in abundance or have a strong fragrance. Herbaceous plants with showy flowers include: daffodils, tulips, daisies, geraniums, impatiens, iris, lilies, pansies, petunias, roses, sunflowers, zinnias and many more.

Abiotic pollination is non-living, physical factors that affect the ability of living organisms to survive. Abiotic factors include winds that spread pollen grains to receptive female flowers, similar to a scattergun approach, that become easily airborne and can travel 20 miles or more on a windy day.

Wind-pollinated plants tend to have relatively small green or brown flowers. The flowers may go completely unnoticed by most people. An example is ragweed, a common allergy producing plant. Many tree and shrub flowers are barely noticed visually, but pack a punch nasally.

A few trees with allergy causing potential include ash (male), cottonwood, elm, hickory, juniper/cedar, mulberry, oak, walnut, pine, poplar (male), sycamore, Russian olive and willow. Trees with showy flowers tend to be pollinated by bees, butterflies and other biotic pollinators. Examples of low or no allergen trees include many of the fruit trees such as apples, crabapples, cherries, pear and plum.

Other allergy causing plants can include Kentucky bluegrass (if allowed to flower), hay and foraging grasses, Timothy grass, pigweed/Portulaca, lamb’s quarter and other weeds.

Plants and pollen are not the only allergy producers in the garden. Molds may cause allergies and can be produced from composts and decomposing bark mulch. Alternatives include buying finished compost instead of making it at home. Replace bark mulch, shredded leaves, cocoa hulls or similar organic material with pebbles. Also, television, radio and print media report pollen counts, so gardeners can garden when the counts are lower.

Other tips include:
• Limit gardening in the afternoon during spring, and early mornings in fall, when pollen counts tend to be highest.
• Remain indoors during windy days during seasonal allergic pollen days
• After working outdoors, wash well or shower, and wash clothes
• Do not hang laundry outside on a line during high pollen periods
• Use an air conditioner if you have one, particularly at night or while driving, and set on recirculate, if possible.
• Wash pets that might pick up pollen outdoors
• Fully clothe yourself, including a cap for your hair; wear a breathing mask when mowing
• Keep windows closed during, and a few hours after, mowing.
• Choose low allergen producing plants to begin with, or replace others in your landscape
• Beware of molds from compost and bark mulches, possibly substituting gravel

Additional information can be found on CSU Extension Fact Sheet #7.002 - Pollination of Tree Fruits, #7.602 - Saving Seed, #5.525 - Nuisance Wasps and Bees, #5.576 - Leaf Cutter Bees, Plant Talk (planttalk.org) #1404 - Bees and Pollination..

The authors have received training through Colorado State University Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

Gardening and Insect Fact Sheets are available on-line by clicking HERE.

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This page updated:  August 5, 2008