A Dozen Tips for Producing Low Allergy
by Thomas Leo Ogren
What we plant often has a direct effect on our own health
and the health of those near us. A pollen-producing male
tree in our own yard will easily expose us to ten times
more pollen than would a similar tree growing just down
the block. This can be compared to second-hand smoke.
It is possible to inhale some smoke from a person smoking
a block or two away from you, but it is hardly the same
as someone smoking right next to you. It is the same with
plants. If your own yard is full of allergenic plants,
then you will be exposed most.
Elementary school landscapes are frequently highly allergenic
because all too often they have been landscaped with trees
and shrubs that will not produce any seeds, seedpods or
fruitwhich the children might want to toss at each
other. What is over-looked is that these tidy choices
are usually male cultivars (clones) and although they
are litter-free, they are prodigious producers
of allergenic pollen. I am now involved with a pollen-free
landscape planting at a new elementary school in Tulare
County, California. This work is being sponsored by their
local asthma coalition and it is very encouraging to see
preventative measures like this being taken. Children
suffer greatly from allergies and asthma, and asthma is
now the most common chronic childhood disease in the US.
Another fine example of low-pollen landscaping surrounds
the new American Lung Association Regional Headquarters
in Richmond, Virginia. With green construction
principles a new Breathe Easy allergy-free
office was constructed. The allergy-friendly landscape
plant materials are predominantly female, and compliment
the clean air building. Other Breathe EasyÔ offices
are also now using pollen free landscapes, as are numerous
Twelve tips: Remember, the greater the exposure to pollen,
the greater the incidence of pollen-triggered allergy
1.Dont plant any male trees or shrubs. These are
often sold as "seedless" or "fruitless"
varieties but theyre males and they all produce
large amounts of allergenic pollen.
2.Do plant female trees and shrubs. Even though these
may be messier than males, they produce no pollen, and
they actually trap and remove pollen from the air. There
is also some very good all-female sod to use for pollen-free
lawns. As an added bonus, these female lawns stay low
and require less frequent mowing.
3.Plant disease-resistant varieties: mildew, rust, black
spot and other plant diseases all reproduce by spores
and these spores cause allergies. Disease resistant plants
wont get infected as much and the air around them
will be healthier.
4.Use only trees and shrubs well adapted for your own
climate zone. Plants grown in the wrong zone will often
fail to thrive. Because they are not healthy, they will
be magnets for insects. Insect residue, "honeydew,"
is a prime host for molds and molds produce allergenic
mold spores. Often native plants will be the healthiest
5.Be careful with the use of all insecticides, fungicides,
and herbicides. Accidental exposure to all of these chemical
pesticides has been shown to cause breakdowns in the immune
system. Sometimes one single heavy exposure to a pesticide
will result in sudden hypersensitivity to pollen, spores,
and to other allergens. This is as true for pets as it
is for their owners. Go organic as much as possible. Make
and use compost!
6.Diversity is good. Dont plant too much of the
same thing in your landscapes. Use a wide selection of
plants. Lack of diversity often causes over-exposure.
Use lots of variety in your gardens.
7.Wild birds are a big plus because they eat so many insects.
Plant fruiting trees and shrubs to encourage more birds.
Suet also attracts many insect-eating birds. Insect dander
causes allergies and birds consume an incredible amount
of aphids, whiteflies, scale, and other invertebrate pests.
8.Use pollen-free selections whenever possible. There
are many hybrids with highly doubled flowers and in many
cases these flowers lack any male, pollen parts. Formal
double chrysanthemums, for example, usually have no pollen.
Another example would be almost all of the erect tuberous
begonias. These have complete female flowers, but their
male flowers have nothing but petals, making them pollen-free.
9.If you simply must have some high-allergy potential
plants in your yard, just because you love them, then
watch where you plant them. Dont use any high-allergy
plants near bedroom windows or next to patios, well-used
walkways, or by front or back doors. Place the highest
allergy plants as far away from the house as possible
and downwind of the house too. Remember: the closer you
are to the high-allergy tree or shrub, the greater is
10.Know the exact cultivar name of a tree or shrub before
you buy it. Dont buy any that are not clearly tagged
with the correct cultivar (variety) name and the Latin,
scientific name. Compare the exact name of the plant with
its OPALS/TM allergy ranking. With this scale, 1 is least
allergenic, and 10 is the most allergenic. Try to achieve
a landscape that averages at OPALS #5, or below.
11.If you have a tree or hedge that has high allergy potential
and dont want to remove it, consider keeping it
heavily sheared so that it will flower less. Boxwood,
for example, has allergenic flowers but if pruned hard
each year, it will rarely bloom at all.
12.Get involved with your own citys tree and parks
departments, and encourage them to stop planting any more
wind-pollinated trees. There are thousands of fine choices
of street trees that do not cause any allergies and we
should be using these instead. Working together we can
make a healthy difference, and well all breathe
better for our efforts.
*Note, with the dioecious plants (separate-sexed) males
cause pollen-allergy, and females because they are pollen
free, do not. Examples of some of these dioecious plants
are: red maple, silver maple, box elder, holly, willow,
aspen, cottonwood, poplar, fringe tree, pepper tree, carob
tree, Osage orange, mulberry, cedar, juniper, podocarpus,
yews, ash, date palms, and even asparagus.
About the Author
Thomas Ogren is the author of Allergy-Free Gardening,
Ten Speed Press. Tom does consulting work on landscape
plants and allergies for the USDA, county asthma coalitions,
and the Canadian and American Lung Associations. He has
appeared on HGTV and The Discovery Channel. His book,
Safe Sex in the Garden, was published in 2003. In 2004
Time Warner Books published: What the Experts May NOT
Tell You About: Growing the Perfect Lawn. His website:
How To Use Hedges In
by Paul Curran
A hedge that is well kept and attractive can do much for
your grounds. Used in the front of the house and on the
sides of your lot, hedges are a barrier against traffic,
noise and all things unsightly; at the same time they
enhance the proportions and general appearance of your
house and lawns. And within the boundaries of your property,
hedges define paths and walks, demarcate various areas,
and help to screen service areas and vegetable gardens.