A flock of evening grosbeaks has been seen at a feeder in Highland Park. The first snow buntings have arrived from the tundra, juncos have joined the house sparrows feeding in our backyard, and the leaves on the huge old cottonwood across the alley are turning from green to gold. You don’t need to be Tom Skilling to notice that fall is here and winter is just behind it.
The reproductive strategy of the eastern cottonwood fits its way of life. It has the live-fast, die-young habits of a pioneering species. Borne aloft on cottony parachutes, its tiny seeds carry little stored energy. They have to land in just the right sort of place to have a chance at survival. For a cottonwood, the right sort of place is a spot where the plant can enjoy full sun. Even a little bit of shade is too much for a newly sprouted seedling. Cottonwoods cannot survive in the shade of their parents, and they quickly die in woodlands. In the Illinois of 200 years ago they would have been confined to open wet areas where fires–they are very fire sensitive–could not reach them. With fire removed from the landscape and treeless vacant lots available everywhere the eastern cottonwood has become the most abundant naturally planted tree in the city.
Best of Chicago voting is live now. Vote for your favorites »
Nonetheless the tree looks healthy. Its crown is broad and leafy. It was a rich green all summer. Cottonwood leaves are glossy and rather stiff, and when the wind blows they clatter instead of rustling. The green is fading now, revealing a bright yellow.
Before long the red and yellow pigments in the leaves will break down, and everything will turn a dull brown. The brown leaves will drop to the ground–and into our gutters–and for the next several months photosynthesis will essentially cease in our part of the world.
