Why Do Leaves Change Color?

leaves

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.

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 treeswhich 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.

Here are the foliage colors of the most common tree species are in the list below.

Oaks

bear oak - yellowish brown
black oak - dull brown
blackjack oak, pin oak, turkey oak - reddish with orange tinge
post oak - brown
red oak - dull brown
scarlet oak - bright scarlet to deep red
Virginia live oak - green this is an evergreen oak)
white oak - orange-brown

Hickories

all hickories have yellow leaves in fall.

Maples

box-elder - yellow, sometimes reddish
red maple - red
silver maple - pale yellow
striped male - yellow
sugar maple - bright orange, turning to yellow

Birches

birches - all turn shades of yellow

Other species

American beech - light yellow and turning brownish tan
American chestnut - brownish yellow
Black tupelo - deep dark red
Bigtooth aspen - orange-yellow, turning pale yellow
Eastern cottonwood - yellow
Eastern sycamore - brown
Flowering Dogwood - deep red
Pin and wild cherries - reddish, turning yellow
Quaking Aspen - yellow varies form pale to deep
Sassafras - reddish becoming yellowish
Sumacs - orange, turning bright red
Sweetgum - orange-red, turing yellow
Tamarack (American Larch) - bright yellow needles
Tuliptree - bright yellow
White ash - maroon, dark reddish green

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.

Fall in PA (Pennsylvania Foliage Watch)

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 .

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