Fall Color Report: Week of August 31, 2009

Howie Neufeld, Ph.D.
Professor of Plant Physiology
Appalachian State University
http://www.appstate.edu/~neufeldhs

Greetings again to everyone in the High Country who is interested in leaf color for the fall of 2009. As I have mentioned in a few radio and newspaper interviews already, it is very difficult to predict how the fall colors will be this year. In part, this is because there is no established science to follow, and as a practicing scientist, this is where I would look first for rationale explanations about fall color quality. However, a search of the peer-reviewed scientific literature finds not a single paper devoted to the factors responsible for good fall color. Instead, fall color predictions in the past have relied mostly on anecdotal accounts, wive's tales, and folk myths, all of which may be popular with the public, but are not that all reliable, nor do they reveal anything about the physiological causes of good fall color. I see the need for a detailed (and funded!) study of the causes of good fall color! Anyone want to sponsor some great research?

Some people think that what happens early in the season determines fall color quality, while others consider mid-summer the key. Yet others (me, for example) think that the four to six weeks prior to mid-October are the most crucial. There is even the idea that if the previous season was excellent, then no matter what happens in the next season, the fall colors simply won't be as good. Kind of like oak trees that produce acorns abundantly in a mast year, and then nearly nothing in the next, even if the weather conditions are identical. And we still don't know the proximate causes of masting in these trees, just as we don't know what factors are really responsible for good fall color.

Unfortunately, we have a better idea of what results in poor fall color than good fall color. If it is a rainy summer or fall, if it is overly warm, or if we have a severe drought, then the color experience won't be as good. Interestingly, the lack of any of these conditions does not necessarily or automatically result in good fall colors! It remains a mystery still!

So, what am I predicting for this fall? This has been one of the coolest summers in recent years. In fact, the upper midwest experienced record cold temperatures in July! Such conditions might contribute to an early fall, and in fact, I have noticed (as of Sep 3rd) that trees on Howard's Knob, just outside Boone, are already beginning to change! So, my first prediction is that fall colors might peak earlier this year than normal. Normal for Boone is about mid-October. This year it might be week or two earlier if present conditions keep up.

However, good fall color, in my humble opinion, will depend heavily on how it goes in September. If September has clear, cool sunny days and cool nights, then my second prediction is that there will be good fall color this year (maybe an 8 or so out of a scale of 10, with 10 being as good as it gets!). If on the other hand, September has a majority of cloudy, rainy days, or, it gets unusually warm, then fall color will be muted (maybe only a 5 or 6). Lastly, if we get near the fall color peak and then get a severe wind or rain storm, that could knock the leaves off the trees, essentially eliminating the fall color season (this happened a few years ago, but not last year, which I rated as a very good/excellent season, or 8.5 out of 10).

Since no one can accurately predict the weather more than a days in advance (sorry, Raysweather!), neither can I accurately predict the quality of the fall color for this year six weeks ahead of time. However, should conditions continue as they have been for these last two days, I am very hopeful!

In future weeks, I will include additional essays about the causes and consequences of fall color, the potential impacts of global climate change on fall color, as well as other tidbits of information about trees (ideas are welcome from readers also, so please send them in and I will compose an essay on that topic for you!). In addition, if you happen to have great digital photos of fall color (particularly single leaves of trees) and would be willing to share them with our readers, do send them in, and if they are of high enough quality, we will post them on our website for everyone to see.

Here's to good fall color for 2009!