Plumping with Pollen
The Ogren Plant Allergy Scale (OPALS™) was developed by Thomas Ogren and has been around since 1999. Apparently the scale is being used by USDA Urban Foresters; the California Department of Health; lung and asthma associations; and a growing number of hospitals, parks, cities, and schools. For example, a female juniper that bears fruit has an OPALS™ ranking of 1 (lowest allergen ranking), whereas a male juniper has an OPALS™ ranking of 10 (highest allergen ranking).
Acres Online, a nursery industry e-newsletter, reported on the OPALS™ scale on Nov. 6: “Pollen is one factor in how allergenic a plant may be, but the scale actually takes into consideration more than 120 individual values. Thomas [Ogren] says male trees are a ‘surefire recipe for huge amounts of urban pollen, allergy, asthma,’ and in some cities, the male to female ratio of separate-sexed landscape plants runs to more than 95% male. The biggest allergy culprits: male mulberry, male juniper, male yew, male ash, male poplars, male willows, male box elder, male-only honey locust, male red maple and male maple hybrids.”
Allergy and asthma sufferers are on the rise. Planting a female plant to capture as much of the male pollen as possible is one way to mitigate some air borne pollen, but making choices based on pollen count and other factors might make gardening more enjoyable for the whole neighborhood. The complete OPALS™ scale is in the book, Allergy-Free Gardening, published by Random House Publishers. Over 5,000 plants are individually allergy-ranked. Visit www.allergyfree-gardening.com for more information.
Have you chosen plants based on pollen count or other allergy factors?