October 2013
The Magic of Gardening

3 Great Trees for Pleasing Fall Color

  Black Gum tree.

It seems as if every year there is a time when we talk about how unusual the weather has been. As I write this article in mid-August, the temperature was a cool 68 degrees in the morning. Our office has been hosting an intern from Germany who was helping us pick bell peppers this morning at the Cullman Research Station. She commented to me that she wished she had packed warmer clothes because she was getting too cold in the morning air. I will be 53 years old when you read this article and I can honestly say I have never heard anyone say with a straight face in mid-August that they were too cold. We may eventually get a real dose of Alabama heat before our intern heads back to Germany, but I told her today she should feel very fortunate.

Most people assume the cooler temperatures will increase the chances for a beautiful array of fall foliage. Temperatures do play a role, but fall foliage color is really quite complicated and not easy to predict. According to U.S. National Arboretum, a wet growing season followed by a dry autumn filled with sunny days and cool frostless nights result in the brightest palette of fall colors. Changes in weather can speed up, slow down or change the arrival time of fall’s colorful foliage. We have certainly had a wet summer so all we need now is a dry autumn and some bright sunny days.

Sourwood tree
(Credit: statebystategardening.com)

You may think a tree’s true color is green, but actually most deciduous species begin to show their true colors in autumn. According to the United States Weather Service NOAA, here’s why: "The four primary pigments that produce color within a leaf are: chlorophyll (green); xanthophylls (yellow); carotenoids (orange); and anthocyanins (reds and purples). During the warmer growing seasons, leaves produce chlorophyll to help plants create energy from light. The green pigment becomes dominant and masks the other pigments.

"Trees must replenish the chlorophyll because sunlight causes it to fade over time. As days get shorter and nights become longer, trees prepare for winter and the next growing season by blocking off flow to and from a leaf’s stem. This process stops green chlorophyll from being replenished and causes the leaf’s green color to fade.

"The fading green allows a leaf’s true colors to emerge, producing the dazzling array of orange, yellow, red and purple pigments we refer to as fall foliage."

  Southern sugar maple tree.

The other critical factor is the species of tree because it has to have the true colors pleasing to look at. There are many great trees producing consistently pleasing fall colors that should be planted more frequently in Alabama. Listed here are three of my favorites. Why not plant one in your landscape this fall? Remember fall and winter are the best months to plant trees and shrubs.

The Black Gum tree (Nyssa sylvatica) is a wonderful native species that tolerates a wide range of soil types, has beautiful red fall color, provides a good nectar source for bees and the female trees produce a small fruit that birds enjoy.

Southern sugar maple (Acer saccharum var. floridanum)looks similar to sugar maple, but is better suited for smaller spaces, hotter summers and poor soils.

Sourwood (Oxydendrum arboretum) is perhaps most commonly found on rocky wooded slopes in the Appalachian Mountains, often growing in combination with other heath family members (e.g., azaleas and rhododendrons) that share the same acidic soil preferences. In cultivation, it typically grows 20-25 feet tall with a straight, slender trunk and narrow oblong crown. Bees love this native tree and you will too. Plant where they will have afternoon shade and morning sun.

Tony A. Glover is a County Extension Coordinator in Cullman County.