A Dozen Tips for Producing Low-Allergy Gardens

Ó 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 fruit—which 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 Heath Houses.
Twelve tips: Remember, the greater the exposure to pollen, the greater the incidence of pollen-triggered allergy and asthma.

1.Don’t plant any male trees or shrubs. These are often sold as "seedless" or "fruitless" varieties but they’re 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 won’t 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 choices.
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. Don’t 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. Don’t 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 your exposure.
10.Know the exact cultivar name of a tree or shrub before you buy it. Don’t 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 don’t 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 city’s 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 we’ll 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.