How Weather Affects Fall Foliage

Only a few days into fall and I've already spotted some red leaves in our backyard. However, this is only the very beginning of fall foliage here in the North Georgia Mountains. My first fall in the south since moving from Connecticut nine months ago, I'll have to wait a few weeks before the hills will ablaze with glorious reds, yellows, oranges, and other fall colors.

Will we here in the North Georgia enjoy a spectacular fall? I'm hoping we will. It was about 11 months ago when we came down here to buy a home in Dahlonega, Georgia. Coming from New England, I didn't expect the brilliant colors I saw last fall (although I do have to admit New England is still the best place for fall foliage.)

But what about this year? We've had a long drought here in Georgia, as well as the rest of the southeast.

Just how much does weather affect fall foliage? And, why do leaves change colors in the fall?

Botanists tell us that plants change as the earth tilts on its axis. This causes reduced light concentration. In addition, the days begin to grow shorter and darker, and the weather grows cooler from about mid-September to mid-October (unless you live in sunny Florida.)

Normally, during the warmer months of spring and summer, plants convert water and carbon dioxide into sugar. This process, called "photosynthesis", simply means that a chemical known as chlorophyll gives plants their green color during spring and summer. Therefore, when temperatures cool and days grow shorter, leaves start to change.

Why are there several colors when leaves change? Let's examine a few fall colors....

Reds---If you notice the progression of colors, you find that red often appears first. That's because cooler nights change the sugars inside leaves to a red pigment, as cooler evening temperatures prohibit sugars from moving out of the leaves. For example, in trees such as maples, sugar (or glucose) is ensnared in the leaves because the process of making plant food (known as photosynthesis) stops.

Oranges and Yellows---Because the days become shorter and drier, as well as the fact that plants discontinue manufacturing food in the fall, the chlorophyll in leaves also disappears. That's when we admire the rich yellows and oranges in place of green leaves. In reality, these colors were inside the leaves in the warmer months of spring and summer, but you couldn't see them as the green from chlorophyll covered them up.

Browns---On the other hand, the brown leaves we see in trees such as oaks are a result of wastes left in the leaves.

What determines whether we'll a spectacular fall?

Fall foliage is different every year, due to weather. When a drought has continued through spring and summer, it's not so much that the leaves won't give a colorful fall foliage. It's just that the health of trees suffers, so the leaves probably won't be as brilliant. In reality, the best fall foliage occurs when dry sunny days of an Indian summer are followed by cool, dry nights.