Know your fall foliage

#Middlebury

On the western side of the trail around Lake Elise, the yellow leaves with touches of orange in the foreground are on an American Beech. Above and behind them, hanging over the trail, the bright red leaves are on a Red Maple. Among the many other species on this trail are witch hazel and several types of oaks. (Curtiss Clark photo)

By JANINE SULLIVAN-WILEY

While out walking with my husband a couple of weeks ago, I noted how some trees were dropping their leaves, even before they changed color. I said, “I think they’re just fed up with the weather this year, and saying ‘I’m done. The heat waves, the drought … I give up. I’m just gonna try again next year.’” He laughed and replied “It’s been that kind of year.” It has been that kind of year for a lot of us.

Have you ever wondered about the science behind the when and how of leaf color changes? The when of the leaves changing color depends on sunlight, which is needed for photosynthesis. As the daylight wanes, and the trees’ source of energy is being lost, the tree begins to seal off its leaves with a corky barrier between leaf stem and branch. Without a flow of water and nutrients, the green chlorophyll in the leaves breaks down, revealing the pigments that remain: the yellows and oranges (carotenoids). Then, in some trees, colors such as red and purple (anthocyanins) accumulate. In the best of years, there is a spectacular progression of vivid colors, even with different colors on the same tree. At the tail end of the process, when all of the pigments have broken down, all that is left is brown (tannins).

The intensity of the color is largely determined by the weather each year. This includes a moist growing season. Without sufficient water, that sealing off process can begin prematurely, resulting in poor color or simply dropped leaves before the color forms (as in my “fed up tree” scenario above).

When this is followed by a dry, sunny fall, with warm days and cool (but frost-free) nights, the chlorophyll will tend to break down more quickly, enabling the underlying colors to show better. We did have a good spring, but the drought and heat waves of this summer were far from ideal. We can hope to salvage what color we can this year with no early frosts or huge storms that will strip the trees bare.

Why don’t you go on a leaf scavenger hunt? Following trails on Middlebury Land Trust properties, see how many of the trees/leaves mentioned below you can find. You can send your findings (a picture to go with it would be great) to this writer or the Middlebury Bee. To make matters interesting, several trees’ leaves can be a variety of colors as they go through phases each fall.

Red leaves include the Eastern flowering dogwood, sassafras (may be yellow), scarlet or red oak, sugar maple (also can be orange) and red maples. Orange leaves can be found on serviceberry (aka shadblow), hornbeam, white oak, silver maple and gray birch. Yellow leaves are found on witch hazel, American beech, hickory, eastern cottonwood, American basswood (aka linden), striped maple, yellow or tulip poplar, yellow and paper birch trees. The Middlebury Public Library has several good reference books available to help you identify trees and leaves.

If you’d prefer a more active experience on the trails and preserves, the MLT has scheduled a second Trails Work day for Saturday, October 17, from 9 a.m. to noon with a rain date of Saturday, October 24. If you joined us in June – please come again! If you missed it, here’s your chance. We will be observing safety precautions including for COVID, and pre-registration is required (jswspotlight@gmail.com).

You can contact this writer at jswspotlight@gmail.com. Visit the MLT on Facebook or the website at middleburylandtrust.org.