Post revised 20 September 2019
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 they die, the pigments that were hidden by the abundance of green, show themselves.
The sequence of color
The Best Fall Color Conditions
Early Cool Weather Brings Early Fall Colors
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 break down, all leaves become brownish.
Each Species of a Plant has its 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.
Regions of the World with Colorful Fall Foliage
Only three regions of the world have the deciduous tree cover that supports the spectacular fall foliage color:
Eastern North America
The British Isles and parts of northwestern Europe
Northeastern China and northern Japan
Specific Regions with Fall Foliage
1. most of southern mainland Canada
2. most of eastern part of United States (New England and small areas of the forest further west)
3. Adirondack, Appalachian, Smoky, and the Rocky Mountains
4. Scandinavian, Northern, and Western Europe north of the Alps
5. the Caucasus region near the Black Sea and Eastern Asia, including much of northern and eastern China, as well as Korea and Japan
Specific Places in the World with Autumn Foliage
New England, USA
Green Mountains, Vermont, USA
Nova Scotia and Quebec, Canada
Cascade Mountains, Pacific Northwest, USA
Catskills, Adirondacks, New York State, USA
Great Smoky Mountains, USA
New Mexico (cottonwood, poplar, aspen trees)
Rocky Mountains, Colorado, USA
Lost Maples State Park, Texas, USA
Burgundy, Provence, France
Slovenia, Julian Alps, Eurasia
The Dolomites, Italy
This Video Explains How Leaves Change Colors in the Fall
Fall Foliage Reports
“Pennsylvania has a longer and more varied fall foliage season than any other state in the nation — or anywhere in the world.” (dncr.pa.gov)
Other regions of the world have more conifer or evergreens trees that don’t have the leaf color changing of deciduous trees.
These websites have foliage changing information.