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Cannon: Checking out the science behind the beautiful foliage of fall

POSTED: September 21, 2012 1:00 a.m.

Have you ever wondered why leaves change color in the fall? It is a simple answer that might amaze you.

Folklore has it that Jack Frost has something to do with it, but in reality, shorter periods of daylight influence the color change.

Leaves change color due to physiological and chemical changes taking place in the plant. Various colors are already present in the plant, but they are hidden by chlorophyll, which gives leaves their green color in the spring and summer months. Chlorophyll must be present in leaves in order for photosynthesis to occur.

What is photosynthesis? That is simply the chemical reaction that enables plants to make food for the plant (glucose, a form of sugar).

There are three other main pigment colors in leaves: carotene (yellow and orange colors), tannin (brown) and anthocyanin (red and purple colors). These beautiful colors shine through as the chlorophyll disappears.

Shorter, cooler days of autumn trigger an end to this process, and the green color of the leaves that is present begins to disintegrate, allowing the fall colors to show through.

The brilliance of the colors then depends on weather conditions, like temperature and moisture. For example, a series of warm, sunny days and cool nights can bring about the best of color display.

Consider your favorite colors when choosing trees and shrubs for their fall color beauty.

If you like red leaves for example, plant flowering dogwood, white oak or red maple. some shrubs that produce red foliage are nandina, fothergilla, oakleaf hydrangea and many types of viburnums.

If bright and golden yellows are your favorite, plant trees like serviceberry, yellow poplar, Japanese maple and river birch. Yellow to orange shrubs include summersweet, witch hazel, fringetree and spice bush.

Of course, there are many other trees and shrubs to choose for their fall color. Remember to look at their growing conditions. Do they like sunny or shady areas? Will the plant have enough growing room?

Planting the right plant in the right space is always a consideration. Autumn-planted trees and shrubs undergo less transplant stress than those planted during the hotter, drier months.

Fall is definitely in the air. Days are shorter, temperatures are cooler and the changing leaves are on the horizon. Look for those patches of reds and yellows dotted among the green landscapes.

Make plans to plant a few of the many types of trees and shrubs that will add colorful fall foliage to your landscape. And don’t forget that drive up into the higher elevations soon to see autumn’s lovely display.

Wanda Cannon serves as Master Gardener coordinator and horticulture assistant for the Hall County Extension office. Phone: 770-535-8293. Her column appears biweekly and on


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