University of Vermont Extension
Department of Plant and Soil Science
MINIMIZING GARDEN ALLERGIES
Dr. Leonard Perry, Extension Professor
University of Vermont
pollen from plants, but also mold, dust, and even scents, can cause allergic
reactions in some people. If you're one of these, you don't have to give up
gardening during part of the season, or have to convert your landscape into
silk flowers, gravel beds, and garden gnomes or plastic flamingos!
Changing some gardening practices, or choice of plants, may be all that's
needed to lessen the symptoms.
to WebMD.com, allergies can have some significant impacts on society. Ragweed pollen has increased in the last 10
to 15 years by four weeks, likely a result of global warming. As a result of hay fever, it's estimated that
4 million workdays are lost each year.
While one in five Americans have symptoms of allergies or asthma, 55
percent test positive to one or more allergens. Allergies, by one estimate,
cost the health care system and businesses $7.9 billion per year. Some asthma in children is induced by
people see the yellow pollen on their car in spring or summer and think that's
what is causing allergies. But this relatively big, showy pollen such as from
white pines isn't really the culprit, but perhaps microscopic pollen that you
don't see, coming from other plants.
Mowing lawns can stir up allergenic particles which may have settled and
accumulated. So, if you find allergies
more pronounced while mowing or nearby, a dust mask may help.
from plants is the main culprit in gardening allergies, and the one we can do
most about. Avoiding exposure to
pollen, either from not planting certain plants, keeping a distance
from those plants that produce irritating pollen, or using
proper culture, are the best means to minimize allergy symptoms.
pollen-producing trees pruned, and allergenic shrubs sheared, both reduce
pollen and allergies. Many don't realize
that the common boxwood shrub has flowers, and that these produce pollen that's
allergenic to some people. It blooms on
second year-old wood, so keeping these pruned yearly keeps the inconspicuous
flowers from forming. Other culture such
as proper placement of plants, watering, fertilizer, and pest control will
reduce insects and diseases. Some may be
allergic to insects, as well as to disease spores.
Thomas Ogren, in his book Allergy-Free
Gardening, uses the phrase "proximity pollinosis", which simply
means that the closer you are to a plant producing allergenic pollen, the
greater your exposure and better chance of symptoms. So not
planting such plants near schools and schoolyards, patios, in public spaces, or
under home windows that you open are all means to reducing allergenic pollen
what plants are best? As with most such
questions, the answer is that it depends.
Allergies, of course, vary with each person as well as with plants. Some
plants with showy, large flowers may have larger pollen that doesn’t blow
around and cause problems, yet others do (such as the catalpa, with large
flowers but small pollen). Some plants
may remain in a young or juvenile state, and never bloom.
If trees have separate sexes, such as ash,
willows, poplars, and some maples, the female plants won't produce any
pollen. Males of the hornbeam, silver,
or box elder maples, junipers, and ginkgo are bad for pollen while their female
plants are fine. (Yet the female ginkgo
produces rather foul-smelling fruit so is seldom found.)
cultivar (cultivated variety) of a plant may produce allergenic pollen, yet
may be sterile or produce no allergenic pollen. "Seedless" trees may not litter the
ground, but they may be males that shed pollen as with some
cultivars of White Ash. For red maples,
'October Glory' or 'Autumn Glory' are among the best for pollen, while you
should avoid 'Autumn Spire', for instance.
'Autumn Fantasy' and 'Indian Summer' are a couple of good Freeman
maples. Some sweet cherries (often the
self-pollinating ones) may cause few problems, yet other cultivars may be
highly allergenic to some people.
Ogren has developed the Ogren Plant Allergy
Scale (OPALS) which you can learn about in his book or website
(www.allergyfree-gardening.com). It rates plants from 1 (low) to
(high) for pollen and allergies and is useful in determining what
plants to buy
if allergies are a concern, with an extensive plant listing in the
book. The scale incorporates many factors, such as
the pollen traits, and whether a plant causes allergies from odor or
related plants may cause allergies.
Perhaps 30 percent of those allergic to ragweed will also be allergic to
the related goldenrod. Some daisy-type
flowers in the composite family cause allergies, such as asters or
chrysanthemums for some people. Flowers
that are closed, and that bees or insects have to enter to pollinate such as
snapdragons, generally don't have pollen that blows about to cause allergies. While one to a few mildly allergenic plants
may not cause problems, an abundance of them may cause hypersensitivity in some
learn more about allergies and their causes from websites of the American Lung
Association (www.lung.org ) or the American Academy of Allergy, Asthma and
Immunology (www.aaaai.org). Sites online
can be useful to track pollen counts and air quality (such as pollen.com or