The leaves are really beginning to change here in Philadelphia.
The leaves of most trees are green during the growing seasons of
spring and summer. During this season, they change from light to dark
green. The green color comes from a substance called chlorophyll.
Chlorophyll absorbs light energy for use in photosynthesis, a
food-making process that occurs in green plants.
The shorter days
and cooler nights of fall signal the end of the growing season. Shorter
days mean less sunlight is available and trees shut down their food
making processes. The chlorophyll breaks down and the green pigment is
no longer seen. But before the they die, the pigments that were hidden
by the abundance of green, show themselves.
The sequence of color
Fall leaf color changes begins at the higher altitudes and progresses to lower altitudes. This is due to the cooler temperatures of higher latitudes and elevations. Trees begin to change along the Canadian border (above this boundary is coniferor evergreen forests) and progresses downward. Leaves change color first in the mountains and move down the mountains into the valleys and coastal areas.
The color changes in predictable order. It begins with the red maples and progresses to aspens to sugar maples to oaks.
The best fall color conditions
Leaf color varies depending on temperature and and other factors. Lack of enough water from droughts and insect eating can case poor foliage display. Warmer than normal October nights are also bad for fall color display. During the warm nights the trees use the sugar produced in their leaves, so not enough sugar is left for color to develop.
Early cool weather brings early fall colors.
The best color displays are developed during sunny fall days and cold, frost-free nights.
If you would like to know when fall foliage colors are at their peak, most Northern and Mid-Atlantic states have hotlines and tourism websites for information.
Brilliant eye-popping colors
The uniform greens give way to the
golds, oranges, reds, purples and bronzes. These pigments are caused by
the following substances.
- yellow color by the pigment xanthophyll
- orange-red tones by the carotene pigments.
- red and purple by pigments called anthocyanins
The
autumn color depends on which of the pigments is most plentiful. As the
chlorophyll and other colorful pigments breakdown, all leaves become
brownish.
Each species of plant has their characteristic fall colors.
Red
and yellow are the main colors of autumn foliage in the east, and
yellow and dark green are the main colors of autumn in the mountains
and hills of the West. The dark green colors are from the numerous
evergreen (conifer) trees.
In the north there are more
deciduous trees and therefore more trees which change color. In the
south are more evergreen species.
In the west, on mountains
and hillsides, the bright yellow quaking aspens are vivid against a
forest of dark green evergreens, such as spruce and fir trees.
In
the east, the predominant colors are the browns of oaks, golds and
yellows of the hickories, sycamores and other species. The reds of red
maples and sumacs typify the October displays and draw many foliage
watching visitors each year.
Falling Leaves
After the it dies the tiny pipelines that carried water and food between the leaf and the rest of the tree become plugged. The cells which held the it to the stem dissolve and separate. The dying leaf hangs by a few strands. These strands dry and twist in the wind. When the strands finally break, it falls to the ground.
Once on the ground, the it is broken down by tiny organisms in the soil. These tiny organisms (bacteria and fungi), convert the leaf into simple substances used for food. These substances are also absorbed by plant roots and provide food for new growth.
The endless circle of life continues .
This year peak foliage is estimated period of full color between October 18 thru 31.
Fall in PA (Pennsylvania Foliage Watch)
