I have always emphasized that the major factors influencing fall color quality and duration include lack of a severe summer drought (we meet that requirement this year!), cooler temperatures (especially at night) and sunny days beginning in late August and continuing through September. We seem to be on track with respect to temperature and sun here at the end of summer – in fact, here in the mountains it seems as if we’ve gone from a hot July right into a cool September, even though we’re still in August. If we don’t’ get a severe wind storm in early October (which can knock the leaves off the trees) we may be on track for a good fall color season – keep your fingers crossed!
Notwithstanding all these requirements, I’m still a little up in the air about both the timing and duration of fall color this year. Take a look at the photo below, which I took on Sunday, August 26, 2012 of the dogwoods across the road from my home. Note that they are in an advanced state of coloration already! And along Rivers Street on the ASU campus, and even scattered throughout Watauga County, I’m seeing sugar maples already switching over to their orange-yellow fall colors! However, the maples change early every year, so I don’t place much emphasis on their ability to predict the timing of the rest of the trees. A few sumacs have also changed, but again, I don’t know if that is due to some other unknown stress or if that is truly a harbinger of an early fall color season.
Will we have an early fall color season? We do know that trees this spring leafed out maybe one or two weeks ahead of their normal time, but what we don’t know is whether that will also translate into also developing fall color one or two weeks early. Perhaps tree leaves have a definite lifespan no matter then they leaf out, and if so, fall colors may occur sooner this year. On the other hand, there is some evidence that trees take advantage of good weather (and rising carbon dioxide levels!) and extend their lifespans further into the fall, which may either delay or keep the timing of fall colors about the same as in previous years. As hard as this may be for me to admit, I simply don’t know what scenario will prevail. We’ll just have to wait and see.
Here in Watauga County, at elevations between 3,300 to 4,000’, fall colors tend to peak in mid-October (somewhere between October 12-14), occurring sooner at higher elevations and later at lower ones. For instance in Asheville, which is about 1,000’ lower than Boone, the peak tends to occur 7 to 10 days later.
The other big unknown is how long good fall colors will persist. The duration of fall colors depends on many factors, including the weather at the time when color quality peaks, the occurrence of severe storms as mentioned above, but perhaps also the growing conditions in the preceding summer (and winter?). This is because these conditions may affect the amount of sugars trees have available to make anthocyanins, the red pigments that most people consider a marker for a good fall color year.
A few years ago, colors peaked on a Friday, and were noticeably reduced by Monday, just three days later, a record short duration! In other years, peak coloration seems to persist for at least a week or more. When we have cloudy, warm days, or severe drought, these reduce sugar levels, which limit a tree’s ability to synthesize anthocyanins, and we get duller reds and a shift over to more orange-yellow colors. When that happens, most people consider those fall seasons to be of lower quality. Seems people prefer it when we have brilliant red leaves contrasted against a deep blue sky or the yellow-orange of other leaves. Why that it is is something for the psychologists to ponder.
As in past years, if you have photos of fall color this year that you’d like to share with everyone, post them on Facebook, or send them to me, and I’ll post them on this page (with your permission of course!). I look forward to sending you reports each week, and they will appear on this Facebook page, my ASU fall color page (http://biology.appstate.edu/fall-colors), on Twitter (fallcolorguy), and also on my fall color blog (http://www.fallcolorguy.blogspot.com/). So, happy watching! As we do every year, everyone here in the High Country looks forward to having you up for what we hope will be a great fall color season! Drive safely!!