Allergy problems are worse today than ever before in our lives. Deaths from asthma continue to climb each year at an alarming epidemic rate.
In our urban landscapes we now have the most manipulated kind of city forest ever seen. In the past twenty years landscapers have grown inordinately fond of using male trees. In dioecious species (separate-sexed) there are separate male trees and separate female ones.
Female trees and shrubs do not produce any pollen, ever, but they do produce messy seeds, fruits, old flowers, and seedpods. Landscapers and city arborists consider this female byproduct to be “litter,” and they don’t like to see it lying on our sidewalks.
As a result we now have huge tracts of these litter-free or “seedless” landscapes in our cities. What these actually are, of course, are male clones. As males their job is to produce pollen, and that they do! Even though in many cities we have less total vegetation than we used to, we have more pollen in our air now than ever before.
In nature separate-sexed plants are usually about 50/50. Half of them are male and half are female. The female plants catch pollen from the air, remove it from circulation, and turn it into seed. Female trees are nature’s pollen traps, natural air-scrubbers.
In our modern cities though, female trees and shrubs are rarely used any longer. Of the five most available street trees for sale now, four of the top five are male clones.
Because no one bothered to consider the effect of the pollen from these male trees, we now have many elementary schools, ringed with male shade trees, and full of asthmatic children. Pollen counts exceeding sixty thousand grains of tree pollen per cubic yard of airspace have been found in elementary school yards. What does this mean? Simply, it means that on these playgrounds, every child there is inhaling several thousand grains of allergenic pollen with each breath of air they take! And people are surprised that childhood asthma is so common now?
In the past “experts” have criticized the concepts of allergy-free landscaping by saying that, “It doesn’t matter what you plant in your own yard. Pollen will just blow in from somewhere else.”
What these so-called experts failed to mention is that the closer you are to the source of the pollen, the more you get. In some ways it is quite similar to second-hand smoke: If someone is smoking a block away from you, yes, some of that smoke might reach you. However, simple common sense tells us that this isn’t at all the same as having someone smoking right next to you. A large male tree in your own yard will expose you to more than ten times the amount of pollen as would a similar tree just down the block.
So what are we to do? In my book, Allergy-Free Gardening, July 2000, Ten Speed Press, I strongly suggest we embrace the politics of pollen. At least five cities in the US now have some form of pollen control ordinance: Tucson, Phoenix, Las Vegas, El Paso, and Albuquerque. We need to do several things and we need to do them quickly.
1. We need city-by-city local ordinances that forbid the further sale and planting of wind-pollinated male clones of trees and shrubs. Enough already!
2. We need to train people in tree grafting so that they can get started changing the multitude of male trees into female trees. Yes, we can give these trees much-needed sex changes and we ought to get with it. This is surprisingly effective and quite easy to do.
3. All landscape plants for sale in nurseries should be required to have a numerical allergy rating on each container. OPALSä already exists and needs to be used. With this system: 1 = least allergenic, and 10 = most allergenic.
4. We need to ask ourselves and our elected representatives these two questions: How much more allergy is acceptable? How many more children need to die from asthma each year before we decide to put an end to these destructive landscape practices?
5. I think the answer is obvious. We need to get started now.