A glimmer of yellow caught my eye. Then another one. And another one. Yes, it was true, those were Aspen leaves I had seen. And they weren’t brown, they were yellow. And yet, it was the first week of August. How could that be?
I already wrote how this past July was one of the driest ones we’ve had in Nederland, well below 50% of normal precipitation. I wondered what this would mean for the Aspens and the fall color change. Well, apparently, I’m getting my answer.
Water is critical to Aspen trees making food for the trees, or producing chlorophyll which is what gives the Aspen leave their green color. Per the Forest Service, “water and nutrients flow from the roots, through the branches, and into the leaves. Photosynthesis produces sugars that flow from the leaves to other tree parts where some of the chemical energy is used for growth and some is stored.” But this year, with so little water, the guess is Aspens would have very little energy left to be stored.
Usually as part of the color changing process, the Aspen will grow a corky membrane between the branch and the leaf stem that stops the flow of nutrients, essentially depriving the tree of food. Once the tree stops getting food, the production of chlorophyll stops which means the end of green leave. In fact the chlorophyll masks the yellows, reds and oranges, so when chlorophyll stops, the beautiful fall colors come out.
I suspect the lack of water is contributing to the Aspen trees losing their nutrient flow earlier, and will prematurely stop photosynthesis and producing chlorophyll. Here in the Colorado Rocky Mountains, we normally expect to see peak fall colors from the third week to September to the first week of October. This year may bring about a very early color change, and in the process disappoint many of our fall visitors who might arrive only to find dead leaves and empty branches.