Health May 13, 2015

Allergy-Free Gardening

How to Curtail That Summertime Sneezing

The breezy, summer weather brings out the gardener in many of us, but, unfortunately, it also brings out the blossoms, swirling pollen and things that make us go achoo! But, take heart. If you are itching to get outside and garden in your backyard, there is a way to take control of your own space and create a more allergy-free landscape.


Choosing plants for backyard landscaping comes down to a bit of “girl power,” according to Thomas Ogren, a California horticulturist and expert on “allergy-free” gardening. Ogren has spent decades researching plants that are troublesome for people with allergies, and he has zeroed in on one of the biggest culprits: male plants that spread their pollen every which way. And we have a lot of them in our cities.

In his newest book, “The Allergy Fighting Garden,” Ogren writes that in the 1940s, the U.S. Department of Agriculture began urging American cities to plant male trees and shrubs on streets and in public parks. The idea was that male plants were tidier and easier to maintain because they don’t produce fruit and seeds that create litter like their female counterparts.

“What was missed,” Ogren writes, “was that these same male trees and shrubs would, of course, all produce allergenic pollen.”  


Ogren’s website,, features a video of him patting the branch of a male cypress tree, and swirling puffs of pollen float from the branch into the wind. Some U.S. cities, like Albuquerque, N.M., have passed pollen control ordinances prohibiting the purchase and planting of such trees.

Ketchum doesn’t have an allergy-free planting policy, according to Jen Smith, director of the Ketchum Parks and Recreation Department. “Ketchum is a small area surrounded by hills and forests that contain a variety of pollen-producing plants,” she said. “I think that an effort to plant only allergy-free plants within the city might be negated by this.” However, Smith encourages homeowners to work with landscapers to create an allergy-free space in their own garden. 

Derek Ruhter, garden center manager with Webb Nursery, agreed that not much can be done about pollen blowing in from the surrounding hills and forests. “Unfortunately, that’s a price we pay for being in the outdoors and as close to nature as we are,” he laughed. 

However, he offered a quick lesson on the three types of plants that homeowners should know about when planning their gardens: monoecious, dioecious and perfectly flowered.

Monoecious (dual sex) plants have separate male and female flowers on the same plant. Some of these plants can be highly allergenic because the pollen from the male flowers must be buoyant enough to float to the female flowers. Examples include oak, cypress, pine, spruce, and juniper. 

Dioecious (single sex) plants are either all male or all female. In most cases, the allergenic pollen from male plants is carried by wind currents to female plants. Plants include ash, willow, poplar, holly, some maples, mulberry, and others. Dioecious females do not produce pollen and are therefore allergy safe.

Perfectly flowered plants have flowers that contain both male and female parts within the same flower, and bees, instead of wind, pollinate them. Examples include lilies, tulips, crabapple, magnolia, and hawthorn. For an allergy sufferer, perfectly flowered plants are a good choice.


One way to select a female plant is to look for flowers, seeds, and pods, although those might not be visible on very young plants. 

A comprehensive guide is OPALS, the Ogren Plant Allergy Scale, now used by, among others, the American Lung Association and the USDA Urban Foresters. OPALS measures the allergy potential of all garden and landscape plants on a scale of 1-10, with 10 being the most allergenic. For example, pansies, petunias and hostas are ranked at 1; male junipers are at 10.

According to Ogren, an allergy-safe garden doesn’t mean ditching all the males, but proximity matters. Consider that male plants next to a door or under an open bedroom window are likely to bring more pollen inside than those located at the other end of the garden.

Ruhter believes allergy-free gardening is an emerging issue that landscapers are still learning about. “The best thing a homeowner can do is to start the dialogue and research the plant material,” said Ruhter. “Your nursery can help you with that. I could see this turning into a big movement,” Ruhter added. “This is definitely one of those things on the horizon.”

This article appears in the Issue of Sun Valley Magazine.