What the fluff? Cottonwoods and other tree seeds


Breaking news. The Extension office is having a snowstorm. In summer? Well, not actual snow, but I would take any moisture right now since we need rain so badly.
But the snow I am talking about is seed snow. And those amazing, statuesque trees in the Farm Bureau’s parking lot with the heart-shaped, aspen-looking leaves, are cottonwoods.
And that is how cottonwood (Populus deltoides) trees got their name. It is all about seed dispersal. Seed dispersal is an amazing part of nature. There are unending ways that Mother Nature has devised to help plants not only make more of themselves, but travel great distances.
This year, that cotton is everywhere. I found it humorous when digging around for information on this column, that out west they call the cottonwood snow, “Devil’s dandruff.” And sadly, whenever nature outdoes herself, there are always some wild rumors that accompany the event.
Someone asked me to confirm what they read on the internet, that this snow was actually some type of genetically engineered new pollen. Sigh, giant eye roll. These questions make me realize two things: (1) There is such a need for real agriculture/horticultural teaching now more than ever; and (2) I have job security.
Of course, the internet fear-mongering statement about cottonwood fluff being GMO danger pollen is preposterous. But as with all urban legends, there is a grain of truth to every tale. In this case, a pollen grain — and pollen — is involved in seed production, including seed production of cottonwoods. But that is the only truth there.
Cottonwoods are among a few trees that are separately sexed. Male trees produce the pollen. Female trees have the flowers that are pollinated then produce a green capsule seed, that when ripe, open to expose the new seed with its flight attendant — the cotton. The cotton fluff is the mechanism by which the seeds travel. This is similar to the seed dispersal of milkweed seed flying on their starlike fluff.
But there can be some danger, or at least some increased bills and thermostat temps, associated with this fluff. The danger is to our venting systems, particularly on HVAC unit condensers. I’m no Ms. Fix-It, but be sure to watch and listen to those programs, and the hot topic the last couple of weeks is warning homeowners to inspect their AC and any other vented systems to be sure to clear any of the cottonwood fluff to prevent the ventilation systems from strangling the intake and clogging.
The intake can become so clogged that the AC struggles to keep up and can eventually overheat. So, take heed, and get out that shop vac or garden hose where needed.
If you like the look of the cottonwood but want to avoid the mess, they have developed male-only varieties that are cotton-less. Similarly, the gingko tree, which is also a single-sexed tree, now has trees that are male only. Why would you not want a female gingko? No, they don’t produce any cotton, and their seeds aren’t a problem, but getting to the seed state is. The flowers of the female gingko have been described as having a fragrance … no, check that, an odor like week-old vomit in a teenager’s gym bag.
When I attended the University of Illinois for my undergrad degree in the ‘70s, everyone warned to steer clear of one area between two buildings during the late spring. Yep, the odor from the female gingkoes in bloom was stifling. But what do you expect from a tree that hasn’t really changed much since the time of the dinosaurs? Having a gingko is to plant a truly ancient tree. It will outlast the planter, and they are magnificent, just be sure your tree is a male.
One other seed-dispersal season we just finished is what I call Mother Nature’s helicopter season. You know when the silver maple trees (Acer saccharinum) rain down their winged seeds, called samuras, or as we called them as kids, whirly-gigs.
Except for this year, in all other years without fail, I get calls from homeowners offering to give me free trees. The first year this happened I was amazed, thinking wow, it is really hard to start most trees from seed, nonetheless. But after a short explanation from the caller, I came to realize that they were talking about the “tree nursery” that their gutters had become. Take about a thousand helicopter seeds from a silver maple, clog a gutter, and get some rain. And, yes, you too could start your own silver maple nursery.
Many people despise the silver maple for its short life (60-80 years) and the heavy seed set, but those trees saved us and were intentionally planted when most of the Eastern half of our country was deforested when the elm bark beetle killed all of the American elms due to Dutch elm disease. We needed a tree that could grow 10 to 15 feet a year to get shade for our then-mostly unairconditioned homes. They were literally a lifesaver.
So, the next time you are shopping for a tree, do some research or contact the Extension office to learn more about the whole tree, including the seeds and their method of dispersal.


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