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Allergies, Asthma and City Trees

admin — Wed, 05 Mar 2008 20:21:12 +0000

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 of the problem is that the arborists and landscape professionals, who plant these trees, often dont know the difference.
The type of trees (and shrubs) used in modern city landscapes has changed dramatically in the past three decades. In the past, the majority of street trees used were perfect-flowered, insect-pollinated trees, such as the once so common American elm tree.
Today though, many of the most widely used city trees are wind-pollinated species. Most of these species are unisexually flowered (dioecious and/or monoecious) and further compounding the 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) on the same tree, also usually produce abundant pollen. It is possible to have all-male trees from the monoecious species. On many species the sexes will be born on separate branches, such as on a Honey Locust tree. If you take cuttings, or budwood, only from the 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 only the top or only the bottom will have either male or female flowers. For example, the bottom half of a mature Italian Cypress for example is all-male. Female
wood is found only at the top of the plant. Thus, scion wood taken from the 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, the 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 1959 the official rate of allergy in the U.S. was between 2 to 5% of the public. By 1999 the official rate of allergy had increased to an incredible 38% of Americans. Asthma, which was once considered rare, is now the number one chronic childhood disease in the US.

Where are Allergies and Asthma the Worst?
The most common allergen of all is pollen and since there are so many more plants growing in the country than in the city, it would make sense then that there is more allergy and asthma in the countryside. Right? No, wrong! Allergies and asthma are far worse in the city than they are in the country.

Several things contribute to this:
1.Pavement makes a poor pollen trap. Pollen in the 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 weakens the 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 within the plant community. In the city there is a preponderance of male trees and shrubs, while in the rural areas there is almost always a complete balance of plant sexuality. The excess of male plants in the city results in an excess of pollen.
6.The very lack of female plant materials in the urban environment also is a prime factor in the 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 and the 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 of the pollen remains airborne.

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. In the past few years several books have been written on the subject and interest is growing rapidly.
With the 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 rank the best number one. Trees that have abundant, highly allergenic pollen, especially those with very long bloom periods, are usually ranked the worst in the 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 ranks the individual cultivars. There are often dramatic allergy differences even between two species in the same genus.

How Are Plants Allergy-Ranked?
OPALS was developed based on the 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, the USDA and the American Lung Association have already use the scale to make better landscaping decisions.
Based on the 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 of the 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 in the air, research shows that most often 99% of a tree’s pollen falls out and sticks within fifty feet of the tree. This means that the closer one is to the pollinating tree the greater the exposure. Thus, the job for arborists is to plant trees that will not expose everyone near them to allergenic pollen.

So, How Do You Tell the Boys from the Girls?
It isnt 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, the sex is predetermined. In the book Allergy-Free Gardening, which is the 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 on the books, although most of these could be improved an updated. Albuquerque, New Mexico is particular interesting, since it has attempted to curb allergies by prohibiting the sale and planting of any male cultivars.
As the public grows more knowledgeable about allergy-free landscapes, municipal arborists and landscape specialists will want to be ahead of the curve. They will want to show their clients that they are well-informed on the subject. In the 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 Back the Pollen Clock, New Scientist, London, Pp. 46, 47, June 3rd, 2000.

About the Author

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

Written By: Thomas Ogren

Asthma Friendly Gardens

admin — Thu, 28 Feb 2008 18:42:02 +0000

Recent studies have shown that babies born to mothers who were exposed to high levels of pollen in their last trimester of pregnancy have a much greater chance of developing asthma. One of the main keys with asthma prevention is avoidance.
When you have asthma the typical garden is not a very friendly place at all. There are mold spores to contend with and worst of all is the pollen. Typical gardens have pollen producing male trees and male shrubs and other plants that can provoke asthma attacks. Almost anyone with asthma will tell you that their asthma can be triggered by a good number of things, but pollen is often number one for causing an attack. Garden allergies are common, but they need not be. Allergies from gardening could be largely a thing of the past if were willing to make some simple changes.
In fall of 1999 in Richmond, Virginia the American Lung Association of Virginia (ALAV) built a new Breathe Easy office and headquarters. They had this entire large building constructed with the latest innovations in green construction and sustainable design. No construction materials were used that would off gas any harmful or toxic chemicals, no materials were used that would trigger asthma or allergies. Every attempt was made to build something that would be pleasant and healthy to work in. The people who work in this office now will tell you too, that they all notice what a great improvement it is. Their office is a healthy building.
The ALA decided it would make perfect sense to landscape their new healthy building (in some states these are now called Health Houses) with an allergy free landscape. OPALS (the plant/allergy 1-10 numerical ranking system) was used to select only those plant materials that were either very low pollen, low allergy, or that were totally pollen free, allergy free. In effect they created the first true asthma friendly garden in the US.
Health Houses in other states are now also adding pollen free landscapes to their green construction, green buildings. A new Health House is about to be built in Pennsylvania, and the PA Association of Landscapers and Nurserymen are helping to surround it with an asthma friendly landscape.
Schools too are getting into the clean air act, and in the city of Visalia, California, the Tulare County Asthma Coalition recently directed the asthma friendly landscaping of a newly built elementary school.
Twelve keys to building your own asthma friendly garden:
1.Plant lots of female trees and female shrubs. Not only will these not shed any pollen, they will also trap a good deal of pollen that may stay in from somewhere else. Think of these female plants as natures air cleaners.
2.Use only low pollen or no pollen lawns. There are types of lawns now that are pretty well pollen free and these are a big improvement over some of the older lawn varieties. In southern states, if you have a common Bermuda grass lawn, consider replacing it with a newer, more asthma friendly hybrid Bermuda grass. Princess 77 is a new Bermuda grass hybrid that can be planted from seed. It is next to pollen free, grows very low and tight, and is especially good looking.
3.With OPALS 1 is best, 10 is worst. Use only plants with rankings of 1-5. The more plants in your gardens that have rankings ranging from 1-3, the friendlier your place will be for anyone with allergies or asthma.
4.Remove any trees or shrubs with rankings over OPALS #7. The woody landscape plants with rankings of 8-10 are all sure-fire allergy triggering plants and you can live without them.
5.Replace any removed high pollen, asthma triggering plants with their opposite, female trees or female shrubs. Also good as replacements are perfect flowered plants that are known to be very low pollen producers. These will all have good (low) OPALS rankings.
6.Use only plants that are well adapted to your own area. If you can find natives that have low allergy rankings, consider using them. Look around your own neighborhood, and see for yourself, which kinds of plants seem to be flourishing there already. For almost every kind of plant used in landscaping, there is now a no or low pollen version of it, if you know what to look for.
7.Use a wide variety of plant materials; diversity is good. Biodiversity always makes sense. The more diverse our gardens are he fewer problems well have with insects and molds.
8.Avoid plants with strong fragrances or odors, as they can cause asthma. Dont plant jasmines or similar vines next to entrances or exits and certainly dont use them underneath bedroom windows.
9.For mulch, use rock or gravel instead of bark to cut down on toxic mold spores in the garden. Flat stones or pavers also make good, mold free mulching materials.
10.To further eliminate mold spores, encourage wild birds in your garden. Virtually all wild birds eat insects, and insect damage triggers outbreaks of mold. Even the tiny hummingbirds actually eat a large number of insects. Put up a hummingbird feeder!
11.Keep your plants healthy. This too will cut down on both pollen and mold. When it is hot and windy, do some irrigating. Fertilize everything in the garden spring and fall. If plants are crowding each other too much, thin them out. If tree branches overhead are putting your whole yard in deep shade, consider having the tree thinned to let in more light. Fresh air and light are the enemies of molds.
12.If a tree, shrub, vine or any other plant always looks sickly, looks dirty, or always attracts bugs, then shovel prune it. Dig it up and get rid of it. Replace it with something easier to grow. Dont get caught up in having to spray insecticides all the time, as they too can easily cause asthma and allergies.

Make your garden a fun, stress free zone. Be sure to have a few comfortable garden chairs to sit in, and a little table of some sort is always good too. Wind chimes, bird feeders, and birdbaths can add greatly to your enjoyment and cost little. A beautiful, pollen free, allergy free, asthma friendly garden can be just the place for healthy children, and a great place for anyone to relax and enjoy the great outdoors. For more advice on low allergen gardening, look up allergy free gardening on the Internet, or go to your local library and read some books on this new important subject.

Tom Ogren is the author of five published books, including: Allergy-free Gardening, Safe Sex in the Garden (Ten Speed Press), and What the Experts May NOT Tell You About: Growing the Perfect Lawn (AOL Time Warner Books). Tom has an MS degree in Agriculture-Horticulture, taught landscape gardening for twenty years, owned and operated two wholesale-retail nurseries, and in northern Minnesota was host of the popular Public Radio call-in gardening show, Tom Ogrens Wild World of Plants!
Tom (Thomas Leo Ogren) has published hundreds of articles on health and gardening. His work has appeared in diverse publications such as South Africas Veldt and Field, in Womens Day, Alternative Medicine, the Burpee Seed Catalog, Sunset Magazine, Landscape Architecture, Der Spiegel, The London Times, The Seattle Times, The Washington Post, and even the Jerusalem Post. He has also made numerous appearances on HGTV and his work was the focus of two made for TV documentaries, one by the Canadian Discovery Channel.
Tom has been interviewed on National Public Radios Weekend Edition and his groundbreaking research was featured on The CBS Evening News. He is a frequent lecturer for garden clubs, arboretums, civic groups, hospitals, medical groups, Master Gardeners, and professional associations of landscapers, landscape designers, writers, nursery people, arborists, and urban foresters. He has become well known for his fun, high energy, highly informative, unusual and provocative talks. Tom is a member of the Professional Landscape Designers Association, and the GWA, the Garden Writers of America. Unlike many well-published authors, he still tries to answer all of his own email. You can contact Tom through his website, at: www.allergyfree-gardening.com

Notice of Copyright: Copyright Thomas Leo Ogren

About the Author

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

Written By: Thomas Leo Ogren

A Dozen Tips for Producing Low Allergy Gardens

admin — Sat, 26 Jan 2008 18:28:01 +0000

What we plant often has a direct effect on our own health and the health of those near us. A pollen-producing male tree in our own yard will easily expose us to ten times more pollen than would a similar tree growing just down the block. This can be compared to second-hand smoke. It is possible to inhale some smoke from a person smoking a block or two away from you, but it is hardly the same as someone smoking right next to you. It is the same with plants. If your own yard is full of allergenic plants, then you will be exposed most.
Elementary school landscapes are frequently highly allergenic because all too often they have been landscaped with trees and shrubs that will not produce any seeds, seedpods or fruitwhich the children might want to toss at each other. What is over-looked is that these tidy choices are usually male cultivars (clones) and although they are litter-free, they are prodigious producers of allergenic pollen. I am now involved with a pollen-free landscape planting at a new elementary school in Tulare County, California. This work is being sponsored by their local asthma coalition and it is very encouraging to see preventative measures like this being taken. Children suffer greatly from allergies and asthma, and asthma is now the most common chronic childhood disease in the US.
Another fine example of low-pollen landscaping surrounds the new American Lung Association Regional Headquarters in Richmond, Virginia. With green construction principles a new Breathe Easy allergy-free office was constructed. The allergy-friendly landscape plant materials are predominantly female, and compliment the clean air building. Other Breathe Easy offices are also now using pollen free landscapes, as are numerous Heath Houses.
Twelve tips: Remember, the greater the exposure to pollen, the greater the incidence of pollen-triggered allergy and asthma.

1.Dont plant any male trees or shrubs. These are often sold as “seedless” or “fruitless” varieties but theyre males and they all produce large amounts of allergenic pollen.
2.Do plant female trees and shrubs. Even though these may be messier than males, they produce no pollen, and they actually trap and remove pollen from the air. There is also some very good all-female sod to use for pollen-free lawns. As an added bonus, these female lawns stay low and require less frequent mowing.
3.Plant disease-resistant varieties: mildew, rust, black spot and other plant diseases all reproduce by spores and these spores cause allergies. Disease resistant plants wont get infected as much and the air around them will be healthier.
4.Use only trees and shrubs well adapted for your own climate zone. Plants grown in the wrong zone will often fail to thrive. Because they are not healthy, they will be magnets for insects. Insect residue, “honeydew,” is a prime host for molds and molds produce allergenic mold spores. Often native plants will be the healthiest choices.
5.Be careful with the use of all insecticides, fungicides, and herbicides. Accidental exposure to all of these chemical pesticides has been shown to cause breakdowns in the immune system. Sometimes one single heavy exposure to a pesticide will result in sudden hypersensitivity to pollen, spores, and to other allergens. This is as true for pets as it is for their owners. Go organic as much as possible. Make and use compost!
6.Diversity is good. Dont plant too much of the same thing in your landscapes. Use a wide selection of plants. Lack of diversity often causes over-exposure. Use lots of variety in your gardens.
7.Wild birds are a big plus because they eat so many insects. Plant fruiting trees and shrubs to encourage more birds. Suet also attracts many insect-eating birds. Insect dander causes allergies and birds consume an incredible amount of aphids, whiteflies, scale, and other invertebrate pests.
8.Use pollen-free selections whenever possible. There are many hybrids with highly doubled flowers and in many cases these flowers lack any male, pollen parts. Formal double chrysanthemums, for example, usually have no pollen. Another example would be almost all of the erect tuberous begonias. These have complete female flowers, but their male flowers have nothing but petals, making them pollen-free.
9.If you simply must have some high-allergy potential plants in your yard, just because you love them, then watch where you plant them. Dont use any high-allergy plants near bedroom windows or next to patios, well-used walkways, or by front or back doors. Place the highest allergy plants as far away from the house as possible and downwind of the house too. Remember: the closer you are to the high-allergy tree or shrub, the greater is your exposure.
10.Know the exact cultivar name of a tree or shrub before you buy it. Dont buy any that are not clearly tagged with the correct cultivar (variety) name and the Latin, scientific name. Compare the exact name of the plant with its OPALS/TM allergy ranking. With this scale, 1 is least allergenic, and 10 is the most allergenic. Try to achieve a landscape that averages at OPALS #5, or below.
11.If you have a tree or hedge that has high allergy potential and dont want to remove it, consider keeping it heavily sheared so that it will flower less. Boxwood, for example, has allergenic flowers but if pruned hard each year, it will rarely bloom at all.
12.Get involved with your own citys tree and parks departments, and encourage them to stop planting any more wind-pollinated trees. There are thousands of fine choices of street trees that do not cause any allergies and we should be using these instead. Working together we can make a healthy difference, and well all breathe better for our efforts.

*Note, with the dioecious plants (separate-sexed) males cause pollen-allergy, and females because they are pollen free, do not. Examples of some of these dioecious plants are: red maple, silver maple, box elder, holly, willow, aspen, cottonwood, poplar, fringe tree, pepper tree, carob tree, Osage orange, mulberry, cedar, juniper, podocarpus, yews, ash, date palms, and even asparagus.

About the Author

Thomas Ogren is the author of Allergy-Free Gardening, Ten Speed Press. Tom does consulting work on landscape 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: What the Experts May NOT Tell You About: Growing the Perfect Lawn. His website: www.allergyfree-gardening.com

Written By: Thomas Ogren