Each year the trees, shrubs, and grasses show off their fall colors that have been hidden all year
long. I'm talking about of course the changing of the leaves. Whether it be the brilliant reds of
a maple or the vibrant yellows of a tulip tree, or deep purples of a sweetgum, the landscape
changes as the cooler, shorter days of autumn arrive. In fact, it’s this time of year when you can
enjoy some of Nature’s best displays painted on a vast outdoor canvas.
|Autumn along the Blue Ridge Parkway in North Carolina
Photo: by David
|A maple tree in brilliant autumn foliage
The timing of the color change varies by the species and location. Sourwood can change to an
eye-catching red in late summer while most other trees are still green. Trees growing at high
elevations will turn color sooner than the same species growing in the low country.
Weather is critical for the fall season of color too. Light, temperature, and water supply have an
influence on the intensity and the duration of fall color. Low temperatures above freezing will
favor anthocyanin formation producing bright reds in maples. An early frost, however, will
weaken the brilliant red color. Rainy and/or overcast days tend to increase the intensity of fall
colors. The best time to enjoy the autumn color would be on a clear, dry, and cool day.
A succession of warm, sunny days and cool, crisp but above freezing nights seems to bring
about the most spectacular color displays. During these days, lots of sugars are produced in the
leaf. A late spring, or a severe summer drought, can delay the onset of fall color by a few weeks.
A warm period during fall will also lower the intensity of autumn colors. A warm wet spring,
favorable summer weather, and warm sunny fall days with cool nights should produce the most
brilliant autumn colors.
|View from Looking Glass Rock
Photo by SCJack
|Whitewater Falls NC
View from lower overlook
Photo by Kelvin Taylor
View from Little Green Mountain
Photo by Rich Stevenson
Autumn is Nature’s last fling before settling down into a winter's sleep. On special years for a
brief time the vivid palette of colors is truly breathtaking.
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The mixture of red, yellow, orange and purple is the result of chemical processes that take place
in the tree as the seasons change from summer to winter. During the spring and summer leaves
produce the food necessary for a tree’s growth. This process takes place inside the leaf with the
aid of a pigment called chlorophyll, which gives the leaf its green color. Chlorophyll is necessary
for photosynthesis, the chemical reaction that enables plants to use sunlight to manufacture
sugars for their food. This extraordinary chemical converts carbon dioxide and water, in the
presence of sunlight, into to carbohydrates, such as sugars and starch.
However, in the fall, because of changes in the length of daylight and changes in temperature,
the leaves stop producing food. The chlorophyll breaks down, the green color disappears, and
the autumn colors become visible to give the leaves their splendor. Red pigments called
anthocyanin give rise to the purplish and reddish fall colors of trees such as sumacs and
dogwoods, while others give the sugar maple its brilliant orange. Anthocyanins give red apples,
concord grapes, blueberries, and, strawberries their color.
The yellow and orange pigments called carotene and xanthophyll give the orange color to
carrots and the yellow color to daffodils and bananas. We don’t see these pigments during the
growing season because they are masked by the abundance of green chlorophyll.
Certain colors are characteristic of particular species. Hickories are golden bronze, dogwoods turn
purplish red and sourwoods and black tupelo gleam with crimson. Maples vary by species: red
maple turns brilliant scarlet; sugar maple, orange-red; and black maple, glowing yellow. Striped
maple becomes almost colorless. The autumn foliage of most oaks turn brown. This is due to
the lack anthocyanin, carotene and xanthophyll.