If you wheeze and sneeze when you set foot in the garden, just think about sex — plant sex, that is. “What people don’t realize is that many plants are either male or female,” says Tom Ogren, pollen expert and author of Allergy-Free Gardening: The Revolutionary Guide to Healthy Landscaping (Ten Speed Press, 2000). “Male plants produce huge amounts of pollen, the biggest allergen, and it’s usually carried on the wind in hopes of reaching a female,” he explains. “Female plants, on the other hand, produce no pollen at all.” Unfortunately, many cultivars in the nursery trade are male because they don’t produce seeds and fruit (deemed messy), but female plants are available and worth seeking out.
Other factors in determining how allergy-causing a plant may be include:
- The type of pollen: Heavy or sticky pollen grains drop close to the plant, while fine pollen drifts far into the atmosphere (and your nose).
- How long the plant produces pollen: Some trees spread their pollen for only a few days, whereas others may go practically non-stop.
- Where the flowers are positioned: Some plants have both male and female flowers. If the male flowers are high up (in corn, for example), the pollen merely has to drop down to the females. However, if the male blooms are at the bottom (as in the castor bean plant), the pollen must drift up, making the plant far more allergenic.
- How the plant is pollinated: Generally, insect-pollinated plants with showy flowers, such as hollyhocks, zinnias and roses, and especially those with tubular blooms (penstemon and trumpet vine), keep their pollen much more to themselves.
To make your garden less allergenic:
- Eliminate or reduce lawn area, and mow only in the afternoon, when pollen levels are lower.
- Plant female trees and shrubs that don’t produce pollen.
- Prune plants such as boxwood and euonymus to remove flowers. Often inconspicuous, greenish flowers are the most allergenic.
- Because mould, spores and scents can also cause allergic reactions, keep plants healthy, eliminating those prone to mould, rust and mildew; reduce the number of ferns you grow; and avoid highly scented blooms.
- Keep high-pollen producers away from the house and seating areas.
Ogren has rated the allergy-causing potential of more than 5,000 plants on a scale of 1 (lowest) to 10 (highest). Among the least troublesome are snapdragons, impatiens, heucheras, hostas, female junipers (Juniperus scopulorum and J. virginiana), female red maples (e.g., Acer rubrum ‘Autumn Glory’), female willows (e.g., Salix matsudana ‘Tortuosa’) and female yews (e.g., Taxus ´media ‘Hicksii’).
The worst include fountain grass (Pennisetum setaceum), male willows (Salix alba ‘Tristis’), Russian olive (Elaeagnus angustifolia), Chinese elm (Ulmus parvifolia) and Japanese cedar (Cryptomeria japonica).
For more plant ratings, consult Allergy-Free Gardening, and for more information, go to allergyfree-gardening.com.
City playgrounds and parks
Pollen expert Tom Ogren is currently conducting an “allergy audit” of a number of Canadian cities, sussing out what plans municipal governments have for implementing sneeze-free landscapes. Plus, Canadian horticulturist Peter Prakke is spearheading a move to create allergy-free schoolyards and parks across the country. Given the incidence of childhood allergies and asthma, not to mention obesity, getting kids playing outside in a safe environment is more important than ever. For details, go to healthyschoolyards.org.