Patterns of Fall Leaf Drop

Patterns of Fall Leaf Drop by Diana Thottungal
Every year we get to see a color show as deciduous trees bed down for the winter. What is less often noticed is that there is a sort of method to the madness. Certain trees have different colors. More surprising, they shed in different ways.
	Left: The photo shows a White Ash that grows near the entrance to the Garden from Wirth Parkway. The inner branches are bare and there is a fringe around the edges. This tree loses its leaves from the inside out. One side is more bare than the other. That’s the side that gets less sunlight and is further along in the shedding process. Right: For contrast, this Maple, shows bare branches at the top. As the season progresses there are more and more branches sticking out as the tree sheds from the top down.
	Left: Yet another variation. This is the exact reciprocal of the Ash. Rather than from inside to out, the American Elm drops its leaves from the outside in, sort of uniformly in all directions. Right: And, yes, there is an exact reciprocal for the Maple. Aspens, and all the Poplars I’ve seen, shed from bottom to top, often with a last leaf or two at the very top, fluttering madly in the November winds.
Right: This Aspen picture was not taken in the Garden or even in Wirth Park, but it shows the Poplar sequence beautifully.
		Left: And, finally, there’s the “You can’t make me” version, in which leaves stay on the tree as long as possible, produce brown tannin pigments and fall off according to no particular pattern. Behold the Oak (and the Beech of eastern forests).
		Diana Thottungal is a naturalist at the Eloise Butler Wildflower Garden. Text and photos copyright © Diana Thottungal 2009. This article was published in The Fringed Gentian™, Vol. 57 #4, Fall, 2009

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