In the early spring the cottonwoods wake slowly. From bare branches and decomposing litter on the ground, grass and buds begin to emerge. When the first leaves are about the size of baby’s hand they allow just enough light in the evening to filter it without blocking it completely. When the light is right, the whole forest glows. And, two weeks later, all the leaves have flushed out and the glow is gone. I watch for that two week window every year.