Cottonwood “cotton” is flying/ Bad CompanyWritten by Thomas Ogren
Cottonwood “cotton” is flying/ Bad Company
Ó Thomas Leo Ogren
I originally saw question below posted in an Internet gardening forum and decided to answer it. It was a question I’d been asked many times before and I knew my answer would be useful in an article on springtime allergies caused by city trees. So I saved it to share with you here.
“Does anyone else here really suffer from allergies when seeds of Cottonwood are flying? I KNOW it is not cottonwood but I am really curious as to what is pollinating at same time.” Diana Pederson, Ingham County, Michigan, Zone 5, United States, author of Landscaping With Bible Plants:
That’s a very good question. Around here, as “cotton” (the seeds) of female poplars (cottonwoods and aspens) and willows is flying about, so is a good deal of pollen from different, unrelated species of trees. It is very common at this precise time that many people are suffering from extreme bouts of hay fever and often it is this “cotton” that gets blame. Some city arborists refuse to plant female willows or poplars because of their firm (if mistaken) belief that this “cotton” is really some kind of pollen. But it isn’t pollen; it is seed. It is NOT what is causing allergies at that time. By time seeds of female willow and cottonwoods are flying, pollen from males of these two species is already spent. However this flying of seed coincides with pollen release of many allergenic plants. Out West this is same time that millions of urban “fruitless” male mulberry trees are shedding their highly allergenic pollen. It is also time that olive trees are starting to release pollen. The cypress trees and shrubs are releasing very large amounts of pollen at this time too, as are many male Ailanthus trees. At or about same time walnut trees are releasing a large amount of pollen, as are many species of hickory, butternut, and pecan. Perhaps most pervasive at this point are oaks, many species of which are still at this time covered with staminate flowers and just loaded with pollen. At same time that female willows and cottonwoods are releasing all that harmless fluff into air, birch trees have just finished shedding large amounts of pollen, much of which is still lying around on ground. In southern areas alders often bloom twice (as will many birch and junipers) and second bloom of alders sometimes will coincide precisely with flying of “cotton.”
CO2, Global Warming, and Pollen-AllergiesWritten by Thomas Ogren
CO2, Global Warming, and Pollen-Allergies
The benefits of added organic matter to soil have long been known and are usually attributed to increased nitrogen, greater water-holding capacity and an increase in activity of soil earthworms and microbes. But experiments have shown that increase in carbon dioxide (CO2) release that accompanies added organic matter is certainly one of main reasons why adding organic matter to soil increases plant growth. Greenhouse owners have long understood that plants consume CO2 and release oxygen. In a greenhouse packed full of plants, through process of photosynthesis, plants can quickly use up most of available CO2 and then their growth slows down or stops. To compensate for this, old time growers used to place boxes or flats of fresh manure underneath their greenhouse benches. As manure decomposed it released CO2 into greenhouse air and plants grew faster as a result. In today’s modern greenhouses, especially those with concrete floors, lack of CO2 is always a concern. Most of newer greenhouse ranges are now equipped with automatic CO2 regulators that monitor amount of CO2 in air inside greenhouse and then release more as needed. In these greenhouses with their gas growth CO2 generators plants don’t just grow bigger-- they also mature earlier.
So, what has all this to do with global warming and allergies?
As we become more and more reliant on burning petroleum products and as our global temperatures continue to rise, carbon dioxide levels in our air are rising. Before last election we in US had assumed, incorrectly, that no matter which candidate won election, new controls were going to be placed on CO2 emissions. We know better now. The US with its huge consumption of fossil fuels, (the U.S. produces nearly 25 percent of man-made carbon dioxide emissions worldwide). also is experiencing greatest increase in CO2. Actually, CO2 accounts for 80-85 percent of heat trapping (greenhouse) gases contributing to global warming. The idea that is now called “Greening Theory” holds that all this extra CO2 is good. It will result in increased plant growth and thus in resulting increases in food supplies. There is some merit to this theory but there are numerous downsides too.
Pollen-Allergies There are many negative effects from global warming but let’s just consider one here, pollen production and it’s affect on allergies. Since 1959 allergies have dramatically increased in US from 2 to 5 percent of population affected, to a whopping 38 percent now. Largely because of huge horticultural “success” of much over-simplified theory of “litter-free” landscaping we already have vast urban landscapes that are heavily loaded with wind-pollinated dioecious male cultivars (clones) of trees and shrubs. These modern landscape trees result in surrounding air with unnaturally large amounts of allergenic pollen. Because “messy” urban female trees are now so rare, almost none of this pollen is now trapped, removed from air and turned into seed. (Female trees produce no pollen, ever, but they do make seeds, pods, and fruit.) We have tidy sidewalks but pollen-filled air. Under normal carbon dioxide levels these male cloned trees will always produce abundant amounts of pollen. Under increased levels of carbon dioxide, they produce considerably more. The increase in temperature itself also results in increased pollen production, and in pollen production that starts earlier in spring and lasts further into fall. There is research that shows that under stress conditions male plants are able to take up more water than are females. Under stress conditions, such as drought, male trees are also able to hold onto water they already have better than are female plants. Where there are abundant water and soil nutrient sources increases in carbon dioxide levels in our air will result in larger urban trees, which if they’re allergy trees, will be capable of producing ever more pollen. Increases in carbon dioxide increase plant growth but only if there is enough available extra water and nitrogen in soil to support this additional growth. When supplies of water and nutrients are not adequate to support this added CO2-induced growth interesting physiological things happen in plants. Foremost, it is an added stress on plants and stress often results in an increase in unusual reproduction factors.