Ahchoo! Summer is here, plants are in leaf and flower, and lots of folks are sneezing. The cause of much of this allergy misery? Contact with grains of plant pollen. What to do if you are among this sensitive lot and you still like to garden? If you want grow your own veggies or plant a garden to help pollinators, are you just making your allergy woes worse? Is there such a thing as allergy-free gardening?
Well, there’s good news and bad news, as they say. The good news is that growing your own fruits, vegetables, and many kinds of flowers is not likely to exacerbate your allergy problems. The bad news – you’re still probably going to encounter some symptom-inducing pollen when you’re outdoors, regardless of what plants you decide to grow.
To understand why, we need to start with a little background info on pollination, the process by which pollen grains produced by the male parts of a flower are transferred to the female parts of the same or a different flower, leading to the eventual formation of seeds. The flowers of some plants are perfect, meaning each blossom carries both male and female parts, while other kinds of plants may have separate male and female flowers on the same plant. Some plants are dioecious, meaning that male and female flowers are borne on completely different plants. The plants with only male flowers produce pollen exclusively, while those with only female flowers bear only fruits and seeds.
Some plants rely on living creatures called pollinators to move their pollen for them. Pollinators are most often insects such as bees, but in some cases birds and even bats act as pollinators! Plants with showy, fragrant, nectar-rich flowers, whether on trees (like apple trees), flowering shrubs (like lilacs), or flowering annuals and perennials, generally have heavy pollen that needs to be moved from one flower to another by pollinators, which is why the plants expend their energy producing blossoms and scent to attract these needed creatures.
Other plants simply toss their pollen out on the breeze and depend on the wind to carry it to receptive female flower parts. Because they don’t need to attract pollinators, their flowers are not showy or fragrant. But because this method isn’t directed, the wind-pollinated plants need to produce large quantities of light-weight pollen in the hope that a small portion will reach its intended targets. Wind-pollinated plants include grasses, many weeds (like ragweed), and nearly all conifers, along with a great many broadleaf trees like aspens, cottonwoods, oaks, ashes, elms, birches, and olives. (And just to keep things interesting, some plants use both strategies to some degree!)
These wind-pollinated plants are the ones causing allergy problems because their pollen is traveling through the air, often for long distances – and up into people's noses. However, not all wind-borne pollen has the same allergenic potential. For example, oak, birch, pigweed and ragweed pollen is considered highly allergenic, while pine and spruce pollen is less so. For those plants that are dioecious, the male plants are the trouble makers, allergy-wise, because every flower they bear is a pollen-producing male. Seedless male clone tree varieties are popular for street and landscape plantings of trees whose female flowers produce a messy litter of fruits and seedpods, for example ash and mulberry (e.g. “seedless” ash and “fruitless” mulberry varieties are pollen-producing male clones).
The pollinator-dependent plants with their showy flowers are generally less of a problem for allergy sufferers because their heavy pollen isn't carried on the wind. This means that most flower and vegetable gardens don't contribute much to allergy issues. Sweet corn is wind-pollinated, but most other vegetables are insect or self-pollinated or are harvested before they produce pollen-bearing flowers (for example, carrots and spinach). And since showy flowers are the point of flower gardens, most of these plants generally do not cause big problems for allergy sufferers. Of course, if you bury your nose into a blossom to enjoy its fragrance, you’ll be exposing your sensitive nose to pollen. And it’s probably best to skip cutting flowers for indoor bouquets that may shed some pollen indoors.
But what about goldenrod, you may be wondering. Isn’t this plant with its showy flowers the cause of lots of late summer sneezing and misery? The answer, actually, is no. Goldenrod has heavy pollen that is ferried from flower to flower by pollinators like bees and butterflies. The real culprit is usually ragweed, a wind-pollinated plant with nondescript, greenish flowers that blooms at the same time as goldenrod. Its highly allergenic pollen wafting on the breeze bedevils hay fever sufferers, while the more eye-catching goldenrod, unfairly, takes the blame.
When you’re choosing plants for your home landscape or schoolyard, it’s a good idea to keep their allergenic potential in mind. When choosing dioecious plants like most ashes and junipers, skip male tree clones and select a female, pollen-free clone, if available. (Check garden references or consult knowledgeable garden store staff to find out which kinds and varieties of plants are wind-pollinated and dioecious.) You’ll probably also want to give ornamental grasses a pass. Take care to locate allergenic wind-pollinated trees and shrubs away from building foundations to reduce the chance of pollen blowing indoors when windows and doors are open. And be sure to keep weeds under control, especially ragweed!
But keep in mind that what's growing in the vicinity of your home or school landscape can also contribute to your allergy woes, and unfortunately, there is not much you can do to stop this “traveling” pollen from reaching your property on the wind. Wearing a mask outdoors when pollen counts are high may help keep you more comfortable, and promptly showering and washing the clothing you wore after outdoor activities will help keep pollen from making its way indoors. Pollen counts are generally highest in the morning, so scheduling gardening or other outdoor activities later in the day may also help.
If seasonal allergies make you miserable, a visit to an allergist for testing can help you identify the specific plants that are most problematic for you and let you fine-tune your plant choices. Finally, check out the website of Thomas Ogren. He is a widely recognized expert in this area and has written a book on allergy-free gardening that rates a wide variety of plants according to their allergenic potential.
And, between the sneezes, enjoy those homegrown fruits and veggies!
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