Why Do Leaves Change Color in the Fall?

The Science Behind the Autumn Scenery

Leaves Change Color in Vermont
••• Temperatures, precipitation and even tree genetics play a role in why leaves change color in the fall. Russell Burden / Getty Images

Want to Know Why Leaves Change Color in the Fall?

 

The truth is... leaves don't really turn color. The colors are there all along!

Leaves get their typically green color from chlorophyll, a pigment found in plant leaves that enables them to process sunlight. Fall's shorter days and cooler temperatures cause the chlorophyll to move from the leaves to the branches, trunk and roots of trees, and the yellow and orange pigments that are always present become gradually visible.

Other chemical processes produce the brilliant reds, purples and bronzes of autumn's palette. On warm fall days, sugar is produced in the leaves of some trees and then trapped by the chill of night. As sugar accumulates, the leaves turn brighter red.

Factors that influence the intensity of fall color the leaves will wear each year include:

  • Rain
  • Amount of sugar in the leaves
  • Wind
  • Temperatures

Weeks of cool, bright sunny days and chilly nights (but no frost) create the brightest colors. The side of a tree exposed to bright sunlight might turn red, while the shady side of the same tree may turn yellow. And cool, sunny autumn days produce brighter colors than warm, wet weather.

Here's a quirky fact that may surprise you: Trees "inherit" their fall colors, just as we inherit the color of our hair and eyes. The color depends on how much iron, magnesium, phosphorus or sodium is in the tree and the acidity of the chemicals in the leaves.

Here are the "inherited" colors for some of New England's most common trees:

YELLOW (caused by the chemical xanthophyl)
Ash, basswood, birch, beech, butternut, elm, hickory, mountain ash, poplar, redbud, serviceberry, willow and some maples (boxelder, mountain, silver, striped and sugar).

RED (caused by the chemical anthocyanin)
Some oaks, some maples, sumac and tupelos.

ORANGE (caused by the chemical carotene)
Some oaks and maples.

RED OR YELLOW
Sugar maple, dogwood, sweet gum, black gum and sourwood.

Why is New England So Famous for Fall Foliage?

New England enjoys some of the most saturated fall colors thanks to its almost pure stands of a few types of trees that all change color at the same time. Trees are not the only thing that contribute to a colorful autumn, though. Shrubs like burning bush and sumac, and even weeds like poison ivy, can paint the roadsides brilliant colors in fall. In Maine, the blueberry barrens turn a phenomenal fiery red.

To truly appreciate fall in New England, get in your car and drive out in the country, hike up the nearby mountains and hills, take a cruise down a river or along the coast, or get on your bike and pedal the back roads. The more time you spend in New England and the more mobile you are, the more likely you are to see colors at their peak.

Planning a New England Fall Foliage Trip? Here's advice to help you decide when to visit.