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

Written by Tom Ogren

Avoiding Allergies by Use ofrepparttar Right Native Plants inrepparttar 110108 Landscape

Many of our most allergenic plants commonly used in landscaping inrepparttar 110109 United States and Canada are indeed natives. However, it isrepparttar 110110 manipulation of these plants by commercial horticulture that has, and is, causing most ofrepparttar 110111 huge increases we are now experiencing with allergy problems. Thirty years ago fewer than 10 percent of Americans had allergies. The official figure today is that a whopping 38 percent of us now suffer from allergies.(December 99, American College of Asthma, Allergy, and Immunology) Not too many years ago death from asthma was fairly rare. Today it is all too common and is considered epidemic. Asthma has now becomerepparttar 110112 number one chronic childhood disease in America. Furthermore, there is new data coming in recently 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.

American Elms The landscape tree in most of America for many years wasrepparttar 110113 tall, stately American Elm. The American Elm used to gracerepparttar 110114 streets of thousands of towns and cities and when DED, Dutch Elm Disease, started to spread and kill off these native elms,repparttar 110115 insect-pollinated, perfect-flowered elms were most often replaced with wind-pollinated, unisexual-flowered, street trees. Many things happened because ofrepparttar 110116 big switch fromrepparttar 110117 elms to these other tree species. First,repparttar 110118 elm flowers had a rich nectar source and since these trees bloomed very early inrepparttar 110119 season, at a time when insect food sources were severely limited urban honeybees and butterflies depended on this food source. Sincerepparttar 110120 majority ofrepparttar 110121 street trees used to replacerepparttar 110122 elms were wind-pollinated, they often lacked these nectaries and supplied no early-season food source. Soon we started to see a rapid decline inrepparttar 110123 total numbers of urban honeybees and butterflies. There were other factors as well behind this decline, pollution, insecticides, and disease, butrepparttar 110124 loss ofrepparttar 110125 crucial early-season food sources should not be underestimated. DED spread mostly from East to West acrossrepparttar 110126 US and so hasrepparttar 110127 rise in allergy rates. You can actually trackrepparttar 110128 spread of allergy fromrepparttar 110129 decline ofrepparttar 110130 elms. The American Elms, Ulmus americana, did cause a certain amount of low-level, early spring allergy, simply because they were so very common. The over-planting of elms resulted in a lack of biodiversity and setrepparttar 110131 stage forrepparttar 110132 massive kill fromrepparttar 110133 DED. We now know that it is always a mistake to use a monoculture, to plant too much of just one species. Diversity is always a good idea in horticulture.

Diversity Biodiversity isrepparttar 110134 way to go when we are creating landscapes that will limit allergenic exposure. Almost any species of plants can eventually cause allergies if it is over-planted enough. All to often in our urban landscapes of today we see that landscapers have usedrepparttar 110135 same old plants over and over again. This overly simplistic approach to landscaping results in landscapes that lack originality and produce a numbing “sameness” to far too much of our urbanscape. When residential houses are professionally landscaped withrepparttar 110136 exact same plant materials used to landscape banks, real estate offices, and dentist’s shops, we all lose. Allergy rates today are far worse in urban areas than they are out inrepparttar 110137 country. Pollen allergies are worse in cities than inrepparttar 110138 country, despiterepparttar 110139 fact that there is much more total green matter inrepparttar 110140 countryside than inrepparttar 110141 city. Plant selection has beenrepparttar 110142 main problem.

Allergies, Asthma and City Trees

Written by Thomas Ogren

Allergies, Asthma and City Trees

Thomas Leo Ogren

Some urban tree species cause an inordinate amount of asthma and allergy problems, while other tree species cause little or no health problems. A large part ofrepparttar problem is thatrepparttar 110107 arborists and landscape professionals, who plant these trees, often don’t knowrepparttar 110108 difference. The type of trees (and shrubs) used in modern city landscapes has changed dramatically inrepparttar 110109 past three decades. Inrepparttar 110110 past,repparttar 110111 majority of street trees used were perfect-flowered, insect-pollinated trees, such asrepparttar 110112 once so common American elm tree. Today though, many ofrepparttar 110113 most widely used city trees are wind-pollinated species. Most of these species are unisexually flowered (dioecious and/or monoecious) and further compoundingrepparttar 110114 problem, thousands of popular cultivars sold today are touted to be “seedless,” “low-maintenance,” “pod-free” or “litter-free.” These fruitless, seedless trees are male plants, all male, and male trees produce prodigious amounts of allergenic pollen. Female trees produce NO pollen what so ever. In dioecious-flowered trees such as most ash, willow and poplars, it is easy to propagate male only trees because they are separate-sexed. Monoecious trees, which in Nature always have both sexes (male and female flowers) onrepparttar 110115 same tree, also usually produce abundant pollen. It is possible to have all-male trees fromrepparttar 110116 monoecious species. On many speciesrepparttar 110117 sexes will be born on separate branches, such as on a Honey Locust tree. If you take cuttings, or budwood, only fromrepparttar 110118 branches with male flowers, then, you'll get an all-male tree. Lots of monoecious Acer spp. cultivars are male-only plants. In a somewhat different way, there are also numerous monoecious species where onlyrepparttar 110119 top or onlyrepparttar 110120 bottom will have either male or female flowers. For example,repparttar 110121 bottom half of a mature Italian Cypress for example is all-male. Female wood is found only atrepparttar 110122 top ofrepparttar 110123 plant. Thus, scion wood taken fromrepparttar 110124 bottom usually produces "seedless" plants. The terms “dioecious,” and “monoecious,” are botanical terms, not horticultural terms. We could perhaps say that a manipulated, asexually propagated all-male cultivar, taken from a monoecious species, is now “dioecious,” but this is not quite correct. A proper dioecious tree is one that in Nature is separate-sexed. These modern engineered trees are never found in Nature. Interestingly,repparttar 110125 first reference in print I ever found to this single sexing-out with monoecious street trees, was in a USDA booklet, from 1982, called “Genetic Improvement of Urban Street Trees.” How Bad Is Allergy Now? In 1959repparttar 110126 official rate of allergy inrepparttar 110127 U.S. was between 2 to 5% ofrepparttar 110128 public. By 1999repparttar 110129 official rate of allergy had increased to an incredible 38% of Americans. Asthma, which was once considered rare, is nowrepparttar 110130 number one chronic childhood disease inrepparttar 110131 US.

Where are Allergies and Asthmarepparttar 110132 Worst? The most common allergen of all is pollen and since there are so many more plants growing inrepparttar 110133 country than inrepparttar 110134 city, it would make sense then that there is more allergy and asthma inrepparttar 110135 countryside. Right? No, wrong! Allergies and asthma are far worse inrepparttar 110136 city than they are inrepparttar 110137 country.

Several things contribute to this: 1.Pavement makes a poor pollen trap. Pollen inrepparttar 110138 city often lands on pavement where wind can cause it to become airborne again. In naturally vegetated areas where there is much more vegetation, pollen often lands on and becomes stuck in grasses, shrubs and vines or in trees. 2.Cities have more air pollution, which weakensrepparttar 110139 immune system and lung function. 3.Stress, which is generally higher in cities, can contribute to both asthma and allergy development. 4.Increased carbon dioxide levels within cities causes pollen-forming plants to produce more pollen with each bloom cycle, and also often causes urban plants to bloom more often. 5.Pollen loads are actually far greater in cities because there is a sexual imbalance withinrepparttar 110140 plant community. Inrepparttar 110141 city there is a preponderance of male trees and shrubs, while inrepparttar 110142 rural areas there is almost always a complete balance of plant sexuality. The excess of male plants inrepparttar 110143 city results in an excess of pollen. 6.The very lack of female plant materials inrepparttar 110144 urban environment also is a prime factor inrepparttar 110145 epidemic of allergy and asthma. Female flowers carry an electrical negative (-) charge (the trees are grounded with their roots) and airborne pollen holds a positive (+) charge. The tree andrepparttar 110146 pollen are mutually attractive; thus a female plant becomes a very effective pollen trap for pollen of its own species. But with almost no female trees and shrubs in modern landscapes, most ofrepparttar 110147 pollen remains airborne.

Cont'd on page 2 ==>
ImproveHomeLife.com © 2005
Terms of Use