Saturday is the first day of Autumn. This is the first of a three-part series on Fall Foliage in New England. Today, I take a look at why the leaves change colors and what ingredients are necessary for optimum viewing of Autumn’s splendor. The next installment looks at the when the colors reach their peak in southwestern Connecticut and New England. Finally, I’ll explore the best places to view the wide array of colors locally and across Connecticut.Autumn officially arrives Saturday morning at 10:49 EDT, and it will begin to feel like it later this weekend after a cold front pushes through the region Saturday night. Temperatures have already fallen into the 40s across interior southwestern Connecticut earlier this week, and Monday's forecast high temperature won't escape the 60s. Naturally, it’s time to look ahead to what this year’s Fall foliage may bring. Have you noticed any leaves beginning to change color yet? I have. And have you wondered if our weather has cooperated to give us optimum colors this Fall? You’re certainly not alone.
I’ve only noticed just a few trees beginning to show their Autumn colors so far. I’m sure you’ve wondered why the leaves change color. All leaves contain a green pigment called chlorophyll, which is instrumental in photosysnthesis. That’s the process in which energy from sunlight is used to make the sugars that feed the tree or plant. During the growing season, it is continually replaced, but eventually it breaks down.
As the days continue to get shorter and cooler, the environment is less conducive to growth. Sunset is before 7:00 p.m. now. Photosynthesis, naturally, is suppressed. Chlorophyll continues to deteriorate, and not much is replaced. The rate of breadown increases dramatically after the first frost. The yellow and orange pigments, known as cartenoids, which have been in the leaves all along, become radiant as the chlorophyll levels continue to decline.
Red and purple pigments, called anthocyanins, develop in late Summer and Fall, largely in response to the first frost. These can be seen in some tree species such as red and sugar maples. Leaves with a variety of chlorophyll levels create the colorful landscape that we’ve come to appreciate in the Northeast in the Fall. The shades of color are also influenced by how the pigments interact with other factors in the leaf, including the pH level and what minerals may be present.
What are the weather factors which ultimately hasten the beauty of the fall colors? The most important factors are sunny, warm days and cool nights. Thus far this month, the average temperature 1.5 degrees above normal. The first nine days this month were warmer-than-normal, but the weather pattern has begun to change. Eight of the last 11 days have been cooler-than-normal. The normal high and low temperatures for southwestern Connecticut today are 72 and 56 degrees, respectively.
Another ingredient necessary for the brilliant colors is rain, and we haven’t had much of that this month. In fact, there have been only five days with measured rain this month, and there has been just one day with measured rain since September 8. Thus far, we’ve received just under two inches (1.91″) of rain for September, which is below the 2.29″ normal through today. August featured below-normal precipitation, too, with 3.33" of rain, well below the 3.96" normal for the month. Cumulatively, for the year, we’ve measured 27.12″ of rain, well below the 31.19″ norm.
Too little rain can cause trees to “shut down” early and cause stress for trees. A quick peek at the week ahead shows that some much-needed rain will arrive Sunday. Next Monday, I’ll take a look at the best locations for viewing the Fall foliage in southwestern Connecticut and Southern New England.
Paul
