Okay, ladies & gentlemen, today you're going to let Uncle Mark take on you on some motherfucking Adventures in motherfucking Botany. As the subject of this entry suggests, this is going to be a weekly installment, for your edification and viewing pleasure. Every week, I will pick out some kind of tree and write up a little essay about it. And remember, kids: Learning is Fun!
This week's tree is the Eastern Cottonwood, Populus deltoides, and were I in a position where I had the authority to do such a thing, I would choose it as the national tree of the United States of America. It is the dominant, indeed nearly the only, tree species throughout much of the traditional American heartland, from the Dakotas down through Nebraska and Kansas and Illinois and into Texas. It is also physically one of the greatest broadleaf trees in North America, a member of that elite club of temperate flowering trees which can regularly grow to heights of more than 100 feet and breadths of more than 4 feet. Furthermore, it is almost a uniquely American tree. Though there are other members of genus Populus spread throughout the globe, P. deltoides has a native range confined almost entirely to the U.S., only peaking into the southernmost reaches of Canada and the very northermonst reaches of Mexico. And the Cottonwood is an incredibly quickly growing tree, capable of shooting up four feet in a single year of growth, a capacity that suits a national symbol of such a great commericial empire as the U.S. well. The cottonwood is also one of those trees that is of more use to Mankind alive than it is dead - which, again, is a nice quality for a national symbol to have. Alive, it has a long history of serving as an excellent windbreak for farms throughout the Great Plains, and a fast-growing tree for urban and suburban streets. Dead, its timber is of low quality and doesn't even burn well. Finally, the cottonwood is an almost perfect aesthetic match for the great plains states. The pale color of its leaves, and the greyish quality its bark possesses, pair well with the tan brown of the plains grasses and the clear unblemished blue of a Dakota sky, creating an atmosphere that is at once terrifyingly harsh and very subdued.
Moving on to more technical matters, the cottonwood is a member of the willow family, the exotically named Salicaceae. Which fact I have always found amusing, because it is among the least "willowy" of trees, instead growing, as I've already mentioned, quite tall and vigorously. In general, it is instantly recognizable by its large, triangular leaves that, like those of many other members of the genus Populus, flutter characteristically (and dramatically!) in the wind, and also by its deeply fissured and cracked bark. P. deltoides is dioecious, which means that it bears male (staminate) and female (pistilate) flowers on entirely seperate plants. Which means that it is entirely legitimate to call any cottonwoods you meet "him" or "her". The flowers come out in the early spring, when the leaves still haven't emerged. Then, later on, in early June, the female trees begin to bear fruit, in one of the more impressive displays of fertility in the vegetable world. They release thousands upon thousands of the cottony-white tufted seeds that give the plant its common name. So productive can they be that, in an area near a large, old cottonwood Madam, the ground may be covered in a snow-like blanket of the seeds, making it look like winter has come six months early.
It was these seeds that made the cottonwood one of the first tree species I ever developed a relationship. When I was in elementary school, the house my family lived in was near several large cottonwoods, and so every year we would get quite an impressive show, made all the more dramatic by the fact that my mother, brother, and I were all allergic to the downy substance that surrounds the seeds. This made the early June a time of sneezing and runny noses in our household, and gave the three of us ample reason to curse those cottonwoods with the worst language we knew. But it also gave us a magnificent spectacle, for those same downy coverings that we cursed are also rather flammable. So my father would find a large pile of seeds and set a match to them, while the rest of the family "ooh'd" and "aah'd" as the entire pile went up in a sudden, brief burst of flame that died down almost as soon as it began.
Ecologically, P. deltoides is, like many members of the Salicaceae, a water-thirsty tree of river banks, stream banks, and wetlands. It is this water that it sucks up like a sponge that fuels its fantastic growth rate. But it can be found in any sufficiently wet woodland environment, and its prodigious growth and equally prodigious seed production allow it to be a major player in the great temperate forests of the East, holding its own against oaks and maples (see this map for the species' range). It is an exceptionally hardy tree, too, tolerant of very poor soils - which is one of the reason why it will thrive in the Great Plains states where few other trees can - and, as befits a water-loving tree of river banks, it has a very strong root system which makes it very resistant to the effects of flooding and erosion. This vigorous root system also makes it great for stream and river restoration projects, while making it a terrible thing to plant in your front yard (as the roots are capable of cracking house foundations and pipes during their insatiable quest for water). All of this toughness also means that it is an exceptional survivor in urban environments, and one will frequently find cottonwoods growing as weed trees in abandoned lots. And, despite its messiness and invasive roots, its rapid growth occasionally makes it attractive as a street tree in areas where a new tree is needed, and quick. Of course, all of this incredible vim and virility comes with a price: cottonwoods are, despite their huge size, seldom very long-lived, as far as trees go, burning themselves out often well before they finish their first century.
Now, if you, my dear, sweet Gentle Readers, will forgive me, I'm going to babble briefly about a subject which I fear everyone besides me will find even more boring than the preceding: taxonomy. P. deltoides is, as I've already mentioned, a member of the willow family, the Salicaceae. Its genus, Populus, is a very complicated one, with several different subgenera. P. deltoides is, according to the latest classification scheme, a member of the subgenus Aegiros, along with the Black Poplar (P. nigra, which gave birth to the famed Lombardy Poplar, about which more in a later entry) of Europe and Fremont's Cottonwood (P. fremontii) of California. The species itself is a conglomeration of what once were several distinct species, such as the Plains cottonwood and the Rio Grande cottonwood, which are still treated as subspecies. The three subspecies are distinguished on such minute criteria as the precise size of the leaves, and so I doubt it will ever be of much importance for anyone other than a professional forester or botanist to distinguish one kind from another. I have, very rarely, seen P. fremontii classified as a fourth subspecies of P. deltoides, but I don't believe that this is currently accepted.
So, there you have it! More information about cottonwoods then I'm sure any of you ever wanted to know. I hope that I haven't bored y'all stiff and you're looking forward to next week's exciting installment of Adventures in Botany.
Exciting your installment since 1986,
--mark
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