Recent information has shown that certain plants used in landscape plantings may be increasing allergy problems for a home or work place. These plants may be causing allergies due to their pollen production. We need pollen. Our world would have significant problems very quickly if pollen was not produced, and if pollinators no longer transported the pollen from one plant to another. Where things go bad is when commercial manipulation of certain plants, especially trees in urban areas, causes over-exposure to pollen and mold spores in the human population. The result is an increase in allergy-suffering. Thirty years ago fewer than 10 percent of Americans had allergies. The official figure today is that 38 percent of us now suffer from allergies. Not too many years ago, death from asthma was fairly rare. Today it is all too common, and is considered epidemic. Asthma has now become the number one chronic childhood disease in America. Furthermore, there is new data coming in that shows a strong connection between over-exposure to pollen and/or mold spores and increases in other diseases such as heart disease, autism, pneumonia, and reflux disease.
Biodiversity (planting more of a variety of plants in our landscapes) is one way to help solve this problem and help limit allergenic exposure. Almost any species of plants can eventually cause allergies if it is over-planted enough. All too often in the urban landscapes of today, we see that landscapers have used the same old plants over and over again. Pollen allergies are worse in cities than in the country, despite the fact that there is much more total green matter in the countryside than in the city. Plant selection has been a main problem. There are many native trees and shrubs used in our landscapes. Maples, oaks, locusts, poplars, willows, catalpas, birch, junipers, and many more native species are extensively used which is often better than using other more exotic species that are out of place for our particular climate and environments.
Unfortunately, the plant breeders and propagators have discovered how to “sex-out” the trees and shrubs used. They have learned to use only male plants, ironically, as “mother plants,” Many plants for sale now are called “seedless,” and they are in effect, all-male clones. The effect of using all male cloned trees and shrubs in our landscapes simply translates to an excess of allergenic pollen. Only male flowers produce this airborne pollen. Unisexual female flowers produce no pollen. Why the Emphasis on Male Plants? Horticulturists knew that female plants produced seeds, seedpods, and fruit. This “litter” falls on sidewalks and creates a “mess”. By using only asexually (no sex involved) propagated cultivars (cultivated varieties), they were able to create “litter-free” landscapes. These require less maintenance, and are very popular with city arborists and the public. In the U.S. today, four of five of the top-selling street-tree cultivars are male clones.
Tom Ogren, an expert in allergy-free gardening, has provided more details about pollen allergy issues in “The Right Native Plants in the Right Landscape Means Fewer Allergies” article which can be downloaded from a recent Wild Ones Journal at www.for-wild.org/download. For more information about Wild Ones- Natural Landscapers, a voice for the natural landscaping movement visit their web site at www.for-wild.org. They can also be contacted by phone, toll free, at (877) 394-3954. Mr. Ogren does consulting work for the USDA and the American Lung Association. His web site is at www.alletgyfiee-gardening.com. In his article, Tom suggests, “NOW is the time to start working on the pollen allergy issue”.