There are many reasons why people suffer allergies from plants – it could be from the air-borne pollen or contact with the plant itself or its pollen. But what do you do about big trees? And what if you don’t even know which plants you’re allergic to? Or maybe you get hay fever and didn’t even know that your garden could be the cause! Usually airborne pollens don’t travel far so the culprits are probably very close to home.

Thomas Ogren, a well-known horticulturist and author of Allergy-Free Gardening and Safe Sex in the Garden, has developed an allergy ranking system – OPALS (the Ogren Plant Allergy Scale), which ranks more than 3,000 common plantings. You can find the scale at www.allegra.com.

One of the very biggest problems of all for allergy sufferers is that most communities have planted all male trees in the interest of avoiding litter and debris that female trees produce, such as seeds, pods, etc. Unfortunately, male trees produce pollen and without female trees to trap that pollen, you have airborne pollen flying around without a place to go except up your nose! So if you have seedless, fruitless trees in your yard or garden, chances are you have male trees. Female trees produce NO pollen and, therefore, are your safest bets for allergy-free gardening. Female plants and trees receive the pollen grains and act like traps or air scrubbers.

Minimize allergens in the garden before you get drastic and start getting rid of offenders. First, if you have a lawn, keep it mowed to about two inches. You don’t want Bermuda grass and Johnson grass in your yard either. If you keep these short, you should be all right – rye, Kentucky Blue grass, and fescue. Also, keep your lawn fertilized so that the grass grows thick and chokes out the highly allergenic weeds like dandelion, nettle, and annual bluegrass.

It’s important to know when pollen counts are high in your garden. The worst times to be out in the yard are on warm, dry, windy days. Try to garden after a long, soaking rain, but wait an hour for the pollen to dampen down. Pollen counts are higher in the morning in fall and in the afternoon in spring.

What if you have a great male tree that you don’t want to take out? You can affect a sex change by hiring an arborist to graft branches from a female tree onto the existing one and in one season your tree will become a pollen-free female tree. It might cost a couple hundred dollars, but then a great tree is worth it. Or try planting female counterparts so you can trap the pollen.

LOW-ALLERGY PLANTINGS
Trees and Shrubs – try dogwood, crabapple, cherry, redbud, magnolia, and female versions of yew, juniper (Bar Harbor, blue point, and Iowa), yew pine, poplar, box elder, some maples (especially female silver and red maples such as Autumn Glory, and October Glory), willow, sour gum, azalea, fir, peach, plum, pear, and ash. Any holly with red berries is also a good choice.
Flowers – best choices are daffodil, iris, hollyhock, impatiens, nasturtium, pansy, begonia, crocus, poppy, tulip, clematis, peony, zinnia, and fully double sunflowers and chrysanthemums. Other herbaceous plants with showy flowers that are OK include daisies, geraniums, petunias, and roses. Perfectly flowered plants don’t cause problems because their pollen is heavy and sticky and is transferred by insects not the air.

WORST OFFENDERS
The worst offenders are male versions of ash, poplar (especially Italian and Lombardy poplars), willow, cedar, juniper, cottonwood, mulberry, box elder, holly, yew, pussy willow, Chinese gingko, smoke tree, seedless honey locust, and berry-less junipers.

Some nurseries are beginning to tag plants with OPALS ratings. Look for plantings rated 3-4 or lower such as Autumn Glory red maple (1), yew trees (1), double hollyhocks (2), and single hollyhocks (3).
If you’re unsure about what in your yard might be causing allergies, take a cutting to a local nursery, to Cooperative Extension Service at either UI or WSU, or hire a horticultural student to come identify what’s on your property.

Pat Diaz gardens on the eastern edge of the Palouse where farmers are already planting their fields.