I had it all wrong about cottonwoods.
I love the sound of the wind in their leaves, a sound that mimics flowing water in the way a rainstick echoes rain. I thought they made that sound because they had double-jointed leaves.
It’s one of those things that stuck in my head – wrong, as it turns out. So when I got next to a cottonwood, and started looking at where the petiole meets the branch, and I couldn’t figure out what makes it different. (The petiole is the part that connects the leaf to the stem. In some plants, like willows, it’s very short. In others, such as cottonwoods, it’s extended.) Since I couldn’t make head or tail out of what I was seeing, I went to my old reliable Sierra Nevada Natural History, and looked it up.
I found the clue under aspen (Populus tremuloides). From its species name, tremuloides, it’s easy to guess what trait is being described. From the genus name (Populus), it’s easy to guess that both aspens and cottonwoods are related to poplars, which have the same trembling leaves. The reason for that, my Sierra Nevada Natural History told me, is that “the leaves, having vertically flat petioles, quiver in any breeze.”
“Vertically flat petioles, vertically flat petioles,” I muttered to myself, unable to configure vertically flat in my mind. So I went out to look.
Vertically flat petioles look like this:
And in action, they look like this:
The wide flat edge acts like a miniature sail, so that the least breeze causes leaves to move, and gives them that unique sound.It could be that this allows their seeds – little bits of white fluff that give cottonwood its name – to be scattered farther, increasing their tribe. In any case the sound of the poplar family is unlike any other, a restful sound, as if I were listening to a brook made of air. Some cottonwoods grow straight up, like their poplar relatives, and others branch out into several trunks. Unlike poplars, however, their crowns are broad and flat.
The bark of the Fremont cottonwood that I was looking at (there are other kinds) is rough and fibrous, a clue to the kind of wood within. A source who knows his firewood told me that it’s next to useless for burning. Since cottonwoods grow only where there’s a high water table, every one of those fibers is filled with water.
So first you have to really dry them out. Then, when you get the into the stove, they burn quickly and dirtily, without much heat, and leave a lot of ash. If you’re looking for firewood, best look elsewhere. But if you’re looking for a sign – and a sound – of water, cottonwoods will take you there.
Leaf buds for next year