Sneezeproofing your landscape

One of my readers likes the look of grasses but is allergic to them, so asked if there are any less-allergenic native grasses.

Pollen causes the allergic reaction, so Thomas Lee Ogren, who has written extensively about allergy-free gardening, said “if people are willing to clip off the flowering stalks before they mature, then the grasses are perfectly fine, and I know some folks who do just this.” Generally the flowering stalks are taller than the grass blades, so once they start growing, it's easy to distinguish them from the clump of grass.

The only grasses that don't produce pollen are female clones of certain grasses, but none of these are commonly available. For instance, saltgrass and a few species of native bluegrass have male and female flowers on separate plants, so if you grew them from seed and planted only the female plants, you could have a nonallergenic native flowering grass landscape.

And if seasonal allergies are a problem, it makes sense to look at the rest of your yard to see if you can replace a few plants to reduce the pollen you breathe in. Ogren observed that allergies have worsened in part because cities have selectively planted the “less messy” male cultivars of street trees, which have no fruit drop and no corresponding female cultivars to catch the pollen. But proximity matters, Ogren said, so what's planted near your doors and windows matters more than what's planted down the street.

Some years ago, he created the Ogren Plant Allergy Scale to rate hundreds of landscape plants. Plants rated 1 or 2 rarely cause allergies, and plants rated 3-4 cause allergy only if you put your nose deep into a flower and inhale. Plants rated 6+ are not recommended as cut flowers in the house, but a few 4-6 rated plants in the landscape should not cause problems. If you have allergies, use sparingly or avoid plants rated 7-8, and replace any plants in your yard rated 9-10. (I'd move before I'd replace an oak!) Here's how some native plants rate on Ogren's scale, from his book Allergy-Free Gardening:

1. carpenteria, heuchera, wild ginger, columbine, viola, shooting stars, mimulus, redwood sorrel, dudleya, strawberry, female currants, female silktassel, female box elder, female cottonwood, female coyote brush, female oso berry
2. fir, allium, clarkia, island bush snapdragon, penstemon, sages, sedum, yucca, evergreen huckleberry, sierra wax myrtle
3. bush poppy, snowberry, douglas fir, toyon, larkspur, manzanitas, yerba buena, wild grape, coffee fern, gilia, azalea, spruce, many bulbs
4. five-finger fern, maidenhair fern, hawthorn, matilija poppy, California poppy, tidy tips, catalina ironwood, nine bark, iris, monarda, pine, styrax, hummingbird fuchsia, bleeding heart
5. vine maple, desert willow, horsetail, groundcover ceanothus, summer holly, dogwoods, redbud, wood fern
6. redwood, sequoia, shrub ceanothus, fremontodendrons, elderberry, male oso berry, ocean spray, lady fern
7. yarrow, birch, buckwheats, holly-leaf and catalina cherry, buckeye, pacific wax myrtle, bay, incense cedar, male silktassels, male currants
8. deciduous oaks, bigleaf maple, blue grama grass, incense cedar, walnut
9. evergreen oaks, Monterey cypress, alders, coffeeberry, junegrass, California sycamore, sagebrush, saltbush, sedges, male cottonwood, male box elder, male coyote brush

© 2010 Tanya Kucak

Next