|
FORESTRY FOCUS: Fall Colors |
|
by Jim Willis |
| Natural Resource Agent |
| Virginia Cooperative Extension Service |
|
September 15, 2000 |
|
It is that time of year again.
Across the state, reporters and reporterettes begin calling
foresters about autumn leaf color.
“What are your predictions for this year?”
“What causes leaves to change color?”
“When will colors be at their peak?”
Invariably, communications get mixed up and some error gets in
the resulting article (Intensity of leaf coloration is not
related to the length of possum toenails).
Consequently, this year, I’ve decided to get a jump on things
and write my own article. First, the predictions. In
2000, yellow-poplar leaves will have a distinct yellow tinge, sugar
maple will show varying degrees of orange and red, and sumac will be
red. Colors will be at
their peak of intensity sometime between October 1 and November 15.
And colors will vary by species and across the region. If all of this seems a tad bit wishy-washy, it is intentional.
Autumn leaf coloration is a complex chemical process.
It begins when nights become long enough to signal the trees
that it is time to start getting ready for winter.
They do this by growing cells, which shut off food and water to
the leaves. As the leaves
die, the green color fades and other colors, which were there all
along become more visible. Eventually,
the leaves die completely and fall to the ground. A number of factors determine the intensity of fall color and
when it will reach its peak. A
hard, early freeze will kill the leaves quickly and result in very
little fall color. Cloudy
days and warm nights keep the green pigment (chlorophyll) from
breaking down and red pigments are not formed very quickly.
Consequently, colors will be “faded” and not very intense.
Wet, windy weather causes leaves to fall early, thus reducing
the show. Dry weather
causes colors to be very bright. And for the best color of all, look for a fairly dry fall
with sunny days and cool nights after a summer of normal rainfall. |