Avoiding Allergies by Use of the Right Native Plants in the Landscape

Written by Tom Ogren

Continued from page 1

Natives and Urban Landscapes There are many native trees and shrubs used in our landscapes. Maples, oaks, locust, poplars, willows, catalpa, birch, junipers, and many more native species are extensively used. Unfortunatelyrepparttar plant breeders and propagators discovered how to “sex-out”repparttar 110108 trees and shrubs. They learned to use only male plants, ironically, as “mother plants,” asrepparttar 110109 source for their scion wood for asexual propagation. First they just used male plants fromrepparttar 110110 dioecious (separate-sexed) species, but later they learned how to produce all-male clones from species that in Nature were never unisexual (the monoecious species). For example, Honey Locust trees, (Gleditsia triacanthos) are native to our Southeastern US. Look at these trees inrepparttar 110111 wild and you will see that all of them are almost always covered with long seedpods. But go to a nursery now and look atrepparttar 110112 Honey Locust trees for sale. The ones on sale now are called “seedless” and they are in effect, all-male clones. What exactly isrepparttar 110113 effect of using all male cloned trees and shrubs in our landscapes? Very simply, this translates to an excess of allergenic pollen. Only male flowers produce this airborne pollen. Unisexual female flowers produce no pollen.

Whyrepparttar 110114 Emphasis on Male Plants? Horticulturists knew that female plants produced seeds, seedpods, and fruit. This “litter” fell onrepparttar 110115 sidewalks and created a “mess.” By using only asexually (no sex involved) propagated cultivars (cultivated varieties), they were able to create “litter-free” landscapes. These required less maintenance and were (and still are) very popular with city arborists andrepparttar 110116 public. Inrepparttar 110117 US today, four of five ofrepparttar 110118 top-selling street tree cultivars are male clones. Female flowers (pistillate) on female trees or shrubs produce an electrical (-) current. Their stigmas are broad and sticky. Airborne pollen from male plants has a negative electrical impulse before release and a positive charge after release, and this pollen is light and dry. Because ofrepparttar 110119 + and – electrical chargesrepparttar 110120 pollen andrepparttar 110121 stigmas are drawn to each other. They are mutually attractive. Mother Nature saw to it that pollen would land, and stick, exactly where it was needed. Female plants are nature’s pollen traps, our natural air-cleaners. Today though, most ofrepparttar 110122 female plants are long gone from our landscapes. The pollen fromrepparttar 110123 males floats about, seeking a moist, sticky, positive-charged target. We humans emit a positive electrical charge, and our mucus membranes, our eyes, skin and especiallyrepparttar 110124 linings of our nose and throat, now trap this wayward pollen. We have becomerepparttar 110125 targets Allergy develops from repeated over-exposure torepparttar 110126 same allergens. If your own yard is full of pollen-pumping trees and shrubs, you and your family arerepparttar 110127 ones who will be exposedrepparttar 110128 most.

Thomas Ogren is the author of Allergy-Free Gardening, Ten Speed Press. Tom does consulting work on for the USDA, county asthma coalitions, and the American Lung Associations. He has appeared on CBS, HGTV and The Discovery Channel. His book, Safe Sex in the Garden, was published 2003. In 2004 Time Warner Books published his latest: What the Experts May NOT Tell You About: Growing the Perfect Lawn. His website: www.allergyfree-gardening.com

Allergies, Asthma and City Trees

Written by Thomas Ogren

Continued from page 1

How to Improve Health and Air Quality through Tree Selection Landscaping to reduce allergies, especially pollen allergies, is an idea that is coming into its own. Inrepparttar past few years several books have been written onrepparttar 110107 subject and interest is growing rapidly. Withrepparttar 110108 addition of OPALS™, (Ogren Plant-Allergy Scale) arborists now have a means to design allergy-free plantings. This scale ranks all landscape plant materials on a simple 1 to 10 allergy basis. Trees that produce zero pollen, e.g., female cultivars, usually rankrepparttar 110109 best – number one. Trees that have abundant, highly allergenic pollen, especially those with very long bloom periods, are usually rankedrepparttar 110110 worst – inrepparttar 110111 9-10 range. There are many trees and shrubs, however, that fall somewhere in between. Using a list of over 100 factors, OPALS™ numerically ranks each species and then further ranksrepparttar 110112 individual cultivars. There are often dramatic allergy differences even between two species inrepparttar 110113 same genus.

How Are Plants Allergy-Ranked? OPALS™ was developed based onrepparttar 110114 following considerations: “What do plants that are well known to cause allergies have in common?” and “What do plants that are well known NOT to cause allergies have in common?” With these two questions it was possible to build two opposing sets of medical-botanical-allergy criteria. One set is positive and one set is negative. Examples of negative criteria: tiny flowers, excerted stamens, small (less than 25 microns in diameter) sized pollen grains, extended bloom period. Examples of positive criteria: complete flowered, sticky, heavy pollen grains, presence of nectaries, brief bloom period. There are now over a hundred criteria used to develop OPALS™ rankings. Individual landscapers, city arborists,repparttar 110115 USDA andrepparttar 110116 American Lung Association have already userepparttar 110117 scale to make better landscaping decisions. Based onrepparttar 110118 plant-allergy scale it is now possible to state, for example, that Acer rubrum – ‘Red Sunset’ maple, is ranked number one and causes no allergies. By comparison, ‘Autumn Spire,’ a male cultivar of red maple does cause allergies and is ranked number nine. Most Pine trees will rank at numbers 4 to 5 and will cause some allergy. Platanus species (sycamore) rank number eight, and cause quite a bit of allergy. A male Canary Island Palm, Phoenix canariensis, which is considered one ofrepparttar 110119 worst at a ranking of 10, will produce an abundance of pollen that will cause severe allergic reactions to many living nearby. Pollen dispersal rates have been measured since 1972 (Gilbert Raynor, NY meteorologist) and although many pollen grains travel far inrepparttar 110120 air, research shows that most often 99% of a tree's pollen falls out and sticks within fifty feet ofrepparttar 110121 tree. This means thatrepparttar 110122 closer one is torepparttar 110123 pollinating treerepparttar 110124 greaterrepparttar 110125 exposure. Thus,repparttar 110126 job for arborists is to plant trees that will not expose everyone near them to allergenic pollen.

So, How Do You Tellrepparttar 110127 Boys fromrepparttar 110128 Girls? It isn’t always that obvious by looking at a tree (especially a young tree) as to whether or not it is a pollen-free female or a pollen-producing male. But since so many city trees are now asexually produced cultivars,repparttar 110129 sex is predetermined. Inrepparttar 110130 book Allergy-Free Gardening, which isrepparttar 110131 result of 15 years of research on this subject, several thousand trees were individually sexed and allergy-ranked. In some cities, pollen control ordinances are already onrepparttar 110132 books, although most of these could be improved an updated. Albuquerque, New Mexico is particular interesting, since it has attempted to curb allergies by prohibitingrepparttar 110133 sale and planting of any male cultivars. Asrepparttar 110134 public grows more knowledgeable about allergy-free landscapes, municipal arborists and landscape specialists will want to be ahead ofrepparttar 110135 curve. They will want to show their clients that they are well-informed onrepparttar 110136 subject. Inrepparttar 110137 future, instead of planting high allergy-trees, they will need to plan and plant ‘healthy’ urban landscapes.

References: 1.Lewis, Walter H., Airborne and Allergenic Pollen of North America, John Hopkins University Press, Baltimore, Maryland, 1976. 2.Jacobson, Arthur Lee, North American Landscape Trees, Ten Speed Press, Berkeley, California, 1996. 3.Koch, Christopher Von, Allergy, Die Woche, pg. 27, July 7, 2000, Hamburg, Germany. 4.Dworschak, Manfred, Der Spiegel, Feind am StraBenrad, Pp. 174, 175, Nr. 29, 2000. 5.Ogren, Thomas Leo, Turn Backrepparttar 110138 Pollen Clock, New Scientist, London, Pp. 46, 47, June 3rd, 2000.

Thomas Ogren is the author of Allergy-Free Gardening, Ten Speed Press. Tom does consulting work on plants and allergies for the USDA, county asthma coalitions, and the Canadian and American Lung Associations. He has appeared on HGTV and The Discovery Channel. His book, Safe Sex in the Garden, was published in 2003. In 2004 Time Warner Books published his latest book: What the Experts May NOT Tell You About: Growing the Perfect Lawn. His website: www.allergyfree-gardening.com

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