Friday, September 16, 2016

Will fall foliage be a washout?

            It’s almost time to start paying attention to the emerging signs that our foliage is about to burst into its fall colors – what one friend refers to as “the hunt for red October.” But this year brings with it great uncertainty. 
The massive defoliation throughout the region by winter moth and gypsy moth caterpillars put great stresses on our trees, as has the considerable drought we have experienced. Both of these factors have made the always difficult job of predicting the timing and brilliance of the fall foliage display even more difficult.
            Local experts tell me that their best guess is that we may experience a slightly muted display this year, and the caterpillars are mostly to blame.

The trees that were defoliated in May and June – mostly in western and southern Rhode Island, and to a lesser degree in the East Bay – produced what botanist Keith Killingbeck calls “a second flush of leaves” in July. Most deciduous plants can do this if the first batch of leaves becomes defoliated early in the season.
But from what Killingbeck has observed, the new leaves appear to be much smaller in size than the mature leaves that were consumed by the caterpillars. And there may even be fewer leaves per tree compared to normal years. This means there is less surface area to magnify the colors. So even if the individual leaves are as beautiful as ever, the trees may not look as stunning.
Killingbeck, a retired professor at the University of Rhode Island, also worries that the process of producing that second flush of leaves required so much energy that the trees may be too exhausted to complete the metabolic processes that produce the colors. In a typical year, the trees suck nutrients stored in the leaves back into the branches and root system before the leaves fall. That, in a nutshell, is what causes the leaves to turn colors. But the trees may not have the energy to go through that process, meaning the leaves may still be partly green when they drop from the trees.
On the other hand, many oak trees appear to have aborted the process of producing acorns this year, which may be a strategy to conserve energy so they can experience a normal fall foliage season.
And if that’s not enough, the severe drought that much of the region experienced might disrupt our fall colors, too.
“What normally happens in drought years is that the leaves are lost earlier than normal, and sometimes if there’s been a severe drought, they turn brown and drop rather than turning brilliant yellow or red,” explained Killingbeck.
The effect of the drought could be reversed, however, if we get a good dose of rain in the weeks leading up to the change of colors. If we do, then the timing of the change and the brilliance of the colors may be unaffected.
Too much rain at the wrong time, though, could also quash the fall colors. Heavy rains during the peak of the foliage season could leach out the compounds that provide the color through tiny fissures in the leaves.
All of which explains why it’s so difficult to predict what to expect from our fall foliage. There are just too many competing factors to take into consideration. So instead of worrying that this year’s colors will be a disappointment, I’m just going to appreciate whatever we get and know that we’ve got another shot at a spectacular display next year.

This article first appeared in the Independent on September 15, 2016.

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