“The allergy landscape is changing,” says allergist Dr. Clifford Bassett, who directs Allergy & Asthma Care of New York. Nationwide, pollen is increasing because plants are growing larger than they usually would. This is because of the increase in carbon dioxide and, in some areas, increased rainfall, he says.
Pollen moves about best on hot, dry days, especially with some wind, says California horticulturist Thomas Leo Ogren. With warmer days and a longer pollen season, “I now often see landscape plants that used to bloom and produce pollen once a year … doing it spring and fall.” Ogren wrote the books Allergy-Free Gardening (Ten Speed Press, 2000) and Safe Sex in the Garden (Ten Speed Press, 2004) about landscaping with allergy-friendly plants. An updated version of his work, The Allergy-Fighting Garden, is due in February 2015.
Ogren writes about the allergy potential from male plants that have been increasing in popularity. “Male trees all produce pollen, lots of pollen, and airborne pollen at that,” he writes. Male plants beckon to gardeners because they don’t tend to produce messy fruit or flowers, leaving less debris than female plants. The human process of weeding out the females in the garden is “unnatural selection,” Ogren writes.
Or, to put it lightly, sexism in the garden can aggravate seasonal allergies, and the worst offenders may be surprising.
“Generally speaking, the plants with the pretty flowers that are fragrant are often the ones that are really more insect-pollinated,” says Bassett. “That means that the scent and the color are to attract insects for pollination.”
In more than 200 pages of Allergy-Free Gardening, Ogren has classified plants by their allergy potential on a scale of 1 to 10, with No. 10 plants being the most likely reasons you reach for the tissues. Ogren calls this trademarked scale OPALS, for Ogren Plant-Allergy Scale. For example, a live oak is rated 9 because it often produces the most pollen of the oaks for the longest time, Ogren writes.
In some cases, Ogren’s scale turns traditional landscaping advice on its head. Bamboo is a great allergy choice (2 rating) because it usually doesn’t flower. Yet it is despised by many because it is invasive and almost impossible to kill. Bradford pears (4) aren’t usually allergens, Ogren says, but they are a poor choice for the Dallas area because wind and ice often cause them to split in two.
Avoid pecan, according to Ogren, because it can cause severe allergies. But Ogren would recommend photinias, at 4 “not a great contributor of allergenic pollen.”
If you listen to Ogren, you will switch from Bermuda grass (10) to St. Augustine (4) and quit planting annual and perennial rye (at 10, an “often severe allergen”). Male junipers are the worst, at a 10, because they can release an explosion of pollen into the air.
“I think, by gardening smart, it can be a more friendly season for you throughout,” says Bassett.
Location, location, location.
Say you are allergic to oak trees. Does it help to avoid planting oaks in your yard? Or even more radically, should you remove them if you already have oaks?
“That’s fine, but the reality is, if they’re not in your yard, your neighbors or even people miles away, those oak tree pollen can be transported miles and, in some cases, hundreds of miles,” says Khan. “So whether you’ve got them in your yard or not may not really make that much of a difference, because you’re still probably going to be exposed to them.”
Bassett says there are really two problems — what’s in your yard and what’s in the region. “Most of the time, pollens blow from great distances. Ragweed and weeds can blow from 300, 400, 700 miles. But local effects are different. And that’s not something a pollen-counting station on the top of a roof of a hospital 15 miles away is going to pick up,” he says.
“Take care of your own yard first,” advises Ogren. “The closer you are, the worse the problem, the larger the dose.”