Gardening Matters

My neighbor’s beautiful Japanese maple tree had me thinking about fall colors and how trees add to the beauty of our homes and neighborhoods. I live in the Heathwood subdivision off Chamblee-Dunwoody Road. Most of our homes were built in the mid-1960s and are around 50 years old. This apparently qualifies us to be considered an “old shade” neighborhood in realtor-speak. (I like the sound of that). And we do have some nice old shade along our streets. Most of our trees are pines and oaks. We also have a nice array of maples, tulip poplars, beech, magnolias and decorative trees like dogwoods, redbuds and cherry.

The last time I had any formal biology lessons was back in the years when John Kennedy was President. It’s been a while. But I do remember the basics lessons about how trees change colors. The short version of those lessons is as follows.

As the summer fades, the days get shorter and the temperature cools down. This signals the trees that it is time to wind down their internal food production process known as photosynthesis. Photosynthesis utilizes sunlight and the green chlorophyll in the tree’s leaves to convert carbon dioxide to oxygen and sugars. The oxygen is given off as a by-product and the sugars are used by the tree to sustain itself. As the photosynthesis process slows down and ends, the tree no longer produces the green chlorophyll in the leaves and the natural color of the leaves can show through.

The yellows and oranges are usually present in leaves all year long, but they are masked by the green chlorophyll. The many shades of red we see are often the result of sunlight converting residual sugars in the leaves to these stunning colors after photosynthesis has dwindled.

Maples are especially known for their range of reddish colors from rusty orange to crimson red.

Oaks usually give us a range of brown shades from taupe to chocolate.

Beech trees hold their parchment colored fall leaves on their branches all winter.

One of my personal favorites, gingkoes, turn a spectacular rich yellow. Even trees such as magnolias add their green color to the broad palette that makes fall trees so beautiful.

I am certainly no whiz at all the science that brings us such wonderful displays as we see in our fall trees. Thus I rely on the comments of experts. According to Wayne K. Clatterbuck, assistant professor in the University of Tennessee’s Division of Forestry, Wildlife and Fisheries, “The amount, duration and brilliance of autumn color depend on weather conditions that occur before and during the time chlorophyll in the leaves is declining. Temperature, light and water supply are the primary factors that influence…bright fall color.”

Given our wet and relatively cool summer this year, we can perhaps expect some changes in the leaf colors this year. My neighbor noted that in previous years her tree produced rich red fall leaves. This year it seems that yellow will be the dominant color of her tree. All of this begs the question of what on-going climate change (regardless of cause) might do to our fall displays. Most of the experts I consulted on the internet seem to feel that they don’t yet really have a clear idea of what might happen in coming years. They generally suggest a wait-and-see regarding any possible changes.

Meanwhile, I plan to enjoy the colors in my ‘old shade’ neighborhood. I hope you can do the same wherever you live.

Jeff Coghill has been gardening in DeKalb County for more than 30 years and has probably killed at least one of each kind of plant he has tried before getting another one to thrive. He is a gardening volunteer at the Dunwoody Nature Center and works closely with members of the DeKalb Master Gardeners group. He can be reached at gardeningmatters@hotmail.com.

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