Our annual show of fall foliage colors began a bit later this season as rainy weather and relatively warm temperatures seemed to have slowed down the initial changes. Sadly, once the process begins, it proceeds far too quickly. I expect peak color to happen sometime around mid-October for the mountain regions in Greene, Ulster and Delaware Counties and perhaps a week to two weeks later for the valley towns. It takes only a few short weeks to go from zero color to peak color. The older I get, the quicker this process seems to occur each year. Roadside trees, which are usually under stress to begin with, are often are the first to change leaf color. I have heard that some people are predicting less than an optimal display, since the wet summer caused lots of foliar diseases on trees such as sugar maples and many of our ash trees have already succumbed to the Emerald Ash Borer. There are some conspicuous bare zones in our forests where entire groves of ash trees have succumbed to this pest.
It is true that many sugar maples have already shed their leaves, somewhat prematurely, but there are still many left to display their typical golden/yellow hues. Other yellow colored trees include the birches, aspen, beech and some of the hickories as well as hop hornbeam (ironwood). Some tree species that have predominantly red color, such as red oak, are among the last to change. Staghorn sumac is showing its typical fiery red color and witch hazel is now bright yellow.
Red maples change color a bit earlier than sugar maple and many of them are already near peak. The pigments that cause the red color, as well as various hues of purple, are called anthocyanins and they really need some cooler weather to develop. These pigments are actually formed in leaves at this time of the year for reasons that scientists do not understand. They are unable to determine what function they play in tree physiology. The pigments responsible for yellow/golden hues are called xanthophyll and carotenoids and they are present all season, but are masked by the green pigment, chlorophyll. It is not until the tree begins to form an abscission layer of cells, cutting off water to the chloroplasts, that the yellow color becomes evident.
Exposure to sunlight affects color as well. The common Virginia Creeper vine turns yellow on the shady forest floor, but assumes a vivid red/purple color when the vines are growing in full sun. Poison ivy behaves the same way. My favorite plant, American ginseng, turns a beautiful golden, yellow color that seems to even glow at twilight. Some have speculated that ginseng’s brilliant fall color allows worthy harvesters to find it only when the roots are fully mature and the red berries have already dropped. If you should happen to come upon ginseng in the forest that still has some bright red berries, please remove the seeds (usually two white seeds) that are inside each berry and plant them nearby, no deeper than ¾ inch in the soil beneath the duff layer. When I find ginseng berries I usually eat the berry pulp and spit out the seeds to plant. I cannot suggest that you do the same however, because there is a ginseng “look alike” plant called “Jack in a Pulpit” that also has bright red berries right now. Ingesting any part of this plant, including the berries will burn your mouth and throat severely. It is not a good idea to taste any wild berries you may encounter, unless you are quite certain what species of plant they are.
Left to reproduce on its own, ginseng has pretty poor success, with perhaps less than one to two percent of the seeds growing into mature plants. This process also requires about ten years to happen, but if you carefully replant the seeds, the success rate can rise to as high as 85%. There are some rather beautiful, but also invasive, plants that produce pretty berries at this time of the year. Asiatic bittersweet is one such plant that I struggle to control on my property, where it has become a serious weed. These twining, woody, vines can form dense thickets that crowd out the other plants nearby. The red berries of bittersweet are enclosed in a bright yellow husk that splits open after frost and remains in place framing the bright red berries. It sure is pretty, but it is also a pretty serious weed in our woodlands!
Reach Bob at rlb14@cornell.edu.
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