Allergy Free Gardening

Editor's note: reprinted with permission. I found this article fascinating .I was blissfully gardening last weekend until I found myself covered in a rash and itching like crazy. It reminded me of some of Tom's wise words of wisdom.
DER SPIEGEL 29/2000, 174-5

An American researcher is examining the allergenic effect of trees and shrubs.His finding: with very little expenditure, city gardeners can alleviate the misery of people who suffer from allergies.

Grey is the city which hay fever sufferers dream about. All grassy places have been cemented over; far and wide no tree, no bush to give off itchy pollen dust. There is a more elegant solution, says American allergy researcher Thomas Ogren. City gardeners must only know what they ought to plant or not plant. Many trees, like chestnuts or lime- trees (linden), only very seldom trigger allergies. But even such notorious pollen-factories as the ash, the poplar, the maple, and the willow are not altogether evil. Some of them will not give off a single grain of pollen in their entire lifetime. Because these types are, as the botanists say, dioecious (zweihausig). Every tree has either male or female blossoms, and only the males produce pollen. So you simply choose the female trees, says Ogren, and people with allergies will be at peace.

Evidently, almost nobody bothers about all this. That astonished the learned agronomist Ogren many years ago--all the more since his wife and his sisters suffered with terrible hay fever. So the researcher took it on himself to begin the work all alone. He resolved to check out the allergenic effect of as many plants as possible. Allergists had for a long time limited themselves to about a dozen plants which cause grief to most of their patients. Among these are alder-trees, grasses and rye. Ogren, on the other hand, studied hundreds of ordinary shrubs, trees and garden flowers. He scratched the skin of all the acquaintenances he could get a hold of, and rubbed them with pollen specimens.

Ogren observed not only how strongly his research subjects reacted to the pollen. He also considered how long the tested plants bloom, and how widely their pollen disperse--how powerfully, therefore, they will affect whole neighborhoods. Each plant finally received a number between 1 and 10:number 1 for "harmless;" number 5 for "of limited duration or only bothersome in the immediate area;" and number 10 for aggressive pollen that torments hay fever sufferers for months at a time.
In a handbook which has just appeared, Ogren presents his value scale. Municipal and private landscape gardeners, Ogren would wish, can henceforth choose their plants from those in the lower register. Here and there a specimen with an index of 5 or 6 might be bearable, but higher than that noone should ever reach.

Luckily, the most compatible plants are usually the most beautiful to behold. Gorgeous flowers entice insects who purposefully carry the pollen further. In contrast, the wind-pollinaters, with their usually tiny, almost invisible, rather greenish blossoms, belong to the arch- enemies of people who suffer from allergies: they scatter their pollen randomly and massively into the winds.The U.S. Department of Agriculture has for many years been using a computer model to explore how vegetation affects the quality of life of inhabitants in cities. The next step ought to be to experimentally build Ogren's Index into that model. In Germany, hardly anyone has cared until now about the allergenic Effect of plants in residential areas. Landscape officials in the cities conform to a generally accepted list of useful street trees, on which one will find a whole multitude of sinners: oaks (8-9 on the Ogren Index), hazel trees (8),alders (9), ash (up to 9, depending on the kind), maples (7-8), and the plane-tree (9), which is always beloved because it makes so little dirt. Chestnuts, on the other hand, which cause allergy sufferers few problems, would not be so ideal, says Hartmut Tauchnitz, spokesman for regional organizations of city landscape gardeners. Chestnut trees let their fruit fall on parked cars. Beech trees, on the other hand, the arch-enemy of runny noses, "now as always belong to the race of beloved street trees," says Tauchnitz. The sand birch has in fact been chosen "Tree of the Year 2000."

Far and wide throughout Germany, birch groves and birch alleys will now be solemnly planted. Only in Freiburg, in the neighborhoods of Rieselfeld and Vauban, is the City Landscape Department willing to forgo, as much as possible, planting trees that can be difficult for the inhabitants. City Gardener Tauchnitz finds this excessive. "I can't be concerned one very street with the three persons with allergies who perhaps live there, "he says. "They're going to suffer in any case." Measurements actutally show that birch pollen often drifts for kilometers in the air. But that doesn't prevent the largest portion of the pollen from falling right around the tree. Researcher Ogren has established that, under birches that stand alone on asphalt surfaces, the ground was golden with pollen at blooming time. A few meters away from the tree, there was hardly a trace of pollen to be found.

The scientific value of this observation may be disputable, but there are hardly any better investigations available. Most of the pollen traps with which the concentration of pollen in the air is measured are usually placed about 15 meters above hospitals and other buildings. They give us very little information about what is happening at the level where breathing is taking place.
Although about 12 million Germans have allergic head colds, it is astonishing how little is known about the circumstances under which this suffering breaks out. What pollen dose triggers it? Is it the sudden gustof wind when a susceptible person passes close to a pollen- bearing birch tree? Or is it rather just the continual haziness which comes from who knows where? The most recent "Special Environmental and Health Assessment" issued by a group of experts appointed by Environmental Minister Trittin laments that there are "considerable gaps in our knowledge."

Only this is clear: the more the pollen which is circulating, the more powerful will be the reactions. When birches blossomed especially luxuriantly this Spring, there appeared "a whole wave of new patients who previously had had no problems," reported the Bochum allergist GerhardSchultze-Werninghaus. However, as long as certain threshold pollen values have not been exceeded, even notorious allergy sufferers have no complaint.

Many professionals are therefore pleading for caution in new plantings. According to the Viennes eallergist Friederich Horak, it would be "absolute imbecillity" to wantonly plant new birch trees. Horak directs the Vienna Allergy Center, where all the measurement data are gathered from the European pollen information agencies. "The principal trigger of allergies in our latitudes is now the birch tree, and nothing else comes even close."

In North America, on the other hand, people with allergies suffer before anything else from a weed called Ragweed. This plant, in German "Traubenkraut," in August and September poisons the air of the whole continent with aggressive pollen--except for a stretch of land in Canada.

The Gaspe Peninsula in the Province of Quebec is free from the burden some growth of the species Ambrosia. In the 1930s, the environmental biologist Elzear Campagna led a successful campaign against the weed there. Hordes of helpers, sometimes armed with flame-throwers, spread out over the narrow tongue of land. Thousands of school children ripped up the ragweed. Today the peninsula is famous as a vacation paradise for tourists with hay-fever.

Germany will soon stand before similar challenges. Allergenic ragweed is spreading throughout Europe. It has already taken root around Lyon, in France. "It is only a question of time until the first plants push over the Danube into Bavaria," says botanist Siegfried Jager, a colleague of Horak in Vienna. Eastern Europe is already as good as conquered. And in Hungary, where more than 20% of the population suffers from hay fever, the dread of a pollen invasion has enkindled a national campaign. The mayor of Budapest lets herds of sheep graze on public lands surrounding the city, so that the animals can chew up the ragweed. And in the whole country a new kind of popular contest has been established: winner is the first one who comes back with 100 ripped up ragweed shrubs.

tr. Thomas E. Ambrogi
29 July 2000