Many people think that allergies are like the weather, there isn’t much we can do about it except complain, but that isn’t true. The most common allergen is pollen, and this we can largely control.

Last Fall I needed some close-up photos of male Coyote Brush groundcover in bloom. Six blocks from my house was a yard full of the drought-tolerant groundcover, so I drove over there and standing on the sidewalk started to photograph the tiny flowers with my macro lens.

An older gentleman came out of the house and asked me, “What in the world would be worth photographing in my yard?”

I explained that I was a horticulturist and an allergy researcher, and that I needed these photos for my new book, Allergy-Free Gardening.

“Are they good ones, or bad ones?” he asked me.

“Bad,” I told him. “These plants are all males and they’re direct relatives of ragweed.”

“That figures,” he said.

“Actually,” I said, looking over his yard, “your entire front yard looks as though it had been designed to cause allergies. Everything here, the Acacia, the Bottlebrush, the male junipers, the Coyote Brush, all of it. Everything except for that climbing rose on your porch.”

He shook his head and I nodded mine. “Do you have allergies?” I asked him.

“No,” he said, “I don’t but my wife sure does. In fact she’s got them right now.”

“I’m not surprised,” I said.

Modern landscapes are stacked with highly allergenic plants. Years ago in almost every American city, the stately American Elm was THE street tree. Dutch Elm Disease swept the land, from East to West, killing off the old elms. The elms did cause some limited allergy but not that much because they were perfect-flowered, with the male and female parts both in the same flower. Elms didn’t shed much pollen and their flowers were insect-pollinated.

The trees that were most used to replace the elms, the ash, oak, sycamores, sweet gums, maples, mulberry, hackberry, poplars, pepper trees, beech, birch, and Zelkova were all wind-pollinated species. In far too many cases all-male clones were used because they were “litter-free” or “seedless.” Female clones, which produce no pollen, are almost never used because they produce seeds, i.e. “litter.” Urban butterflies and honeybees, once common, began to disappear as their main early spring food source vanished, replaced with non-nectar bearing, wind-pollinated trees.

As pollen levels in cities have increased, the cases of hay fever and asthma have also grown, skyrocketing from 10 percent thirty years ago, to an astonishing 38 percent today. (American College of Allergy, Asthma, and Immunology, December 1999) Each year more of these replacement trees reach sexual maturity, and as they come into bloom more and more people come down with allergies.

Roses have long had a mostly undeserved bad rap as the cause of much allergy. Some roses, however, do cause a limited amount of allergy. The sweet, heavy fragrance of a rose like Double Delight, so pleasing to most of us, can make perfume-sensitive folks ill.

Pollen from some rose cultivars does become airborne and is often picked up in aero-samples. Wild roses tend to produce much more of this airborne pollen than do our domestic hybrids. Roses that have many petals do a fairly good job of hiding most of the pollen-laden male stamens, although even most double roses will expose some pollen when they are fully open. Some rose cultivars with extremely high petal counts are lacking the pollen-bearing stamens altogether.

Anyone with allergies would be wise not to directly sniff the fragrance of a rose, unless the flower is either in the bud or half-open stage. Roses that are fully open can indeed directly expose one to a good dose of pollen, and this is especially true of roses that are past full bloom and starting to fade.

Because I have bred my own hybrid roses for a decade now, I have discovered that all roses are not equal when it comes to the amount of pollen they produce. Certain roses (the old double pink Cecile Brunner is a good example) produce almost no viable pollen. A rose breeder may need to use the stamens of thirty or more blooms of Cecile Brunner in order to get enough pollen to make one single cross. This, of course, means that Cecile Brunner is a very fine rose indeed for those who are especially allergic to pollen.

Another thing that we look for in allergy-free or low-allergy roses is ability to thrive without much attention. Roses that constantly need to be sprayed with fungicides or insecticides are not good candidates for allergy-free gardens. Pesticides can trigger allergies, and in some cases exposure to pesticides, both organic and inorganic, can directly cause initial hyper-sensitivity to other allergens. Furthermore, mildew itself is an allergen, as is rust. Likewise, soft-bodied sucking insects such as aphids produce “honeydew,” on which spore-producing molds thrive. Low-allergy roses are usually the ones that are the easiest to grow.

In my book, Allergy-Free Gardening, gardeners will find the first ever plant-allergy scale. This trademarked scale, OPALSä, short for Ogren Plant Allergy Scale, rates all garden and landscape plants on a one to ten basis. A rating of one represents a plant with almost no potential to trigger allergy. A plant ranked at ten is one that can be counted on to produce a great deal of severe allergy. OPALSä is now being used by the USDA urban foresters in Syracuse, New York, who are creating city-by-city numerical pollen-allergy projections for the entire United States.

Most roses will rank from two to five - quite good, on the OPALSä scale.

Rose lovers are often exposed to much more pollen from their choice of trees, shrubs, ground covers, lawns, and vines, than they are from their roses. Certain woody plants like male cultivars of willow, ash, maple, juniper, podocarpus, mulberry, box elder, and pepper trees will produce far more allergenic pollen than any roses. Other wind-pollinated species such as alder, walnut, sycamore, olive, and oak also produce a great deal of pollen.

Some vines and ground covers, honeysuckle is a good example, frequently are implicated as allergy causing. Lawns that are weedy or not kept mowed will produce allergenic pollens.

We now have available many asexually-propagated cultivars of all kinds of plants that produce no pollen at all. There are hundreds of named varieties of shrubs and trees that are female and non-pollinating. There are also others that simply never bloom, such as the non-allergenic olive variety, ‘Swan Hill.’ These non-bloomers of course produce no pollen.

If a gardener knows where to look, there are even sod lawns to buy now that are completely pollen-free. These wonderful, allergy-free lawn grasses come from numerous species of grasses that will flourish in cold areas, hot, dry regions, and even some for salty or soggy areas.

Creating an allergy-free rose garden takes some care and knowledge. Roses that thrive in one region may not do well in another and some of this is best learned from actual hands-on experience.

Whether we have allergies ourselves or not, landscaping to limit allergenic pollen is a highly considerate, civilized way of doing things.