The sweet gum tree has a moderate growth rate, and is used as a shade tree or specimen planting. It requires a large planting site such as parks, campus settings, or on large residential properties. This lovely pyramid-shaped deciduous tree is native to North America, and is hardy in zones 5B through 10A. It is susceptible to canker diseases, leaf spots, and leader dieback.
The scientific name for sweet gum is Liquidambar styraciflua. A mature sweet gum tree can reach a height of 60 to 75 feet, and a width or spread of 35 to 50 feet. The foliage is star-shaped-leaves, which reach 4 to 8 inches in length. Leaf color is green during the growing season, turning orange, purple, red or yellow depending upon the variety/cultivar of sweet gum tree. Spring flowers are inconspicuous. The fruit of the sweet gum tree is round and from 1 to 3 inches in size with a brown color. This tree will grow in full sun, partial sun or partial shade.
There are several cultivars of sweet gum available. Two cultivars that are found in southern regions are Burgundy (glossy green leaves turning burgundy in the fall), and Festival (peach fall color). Of the various cultivars, the most cold hardy is Moraine. Palo Alto is known for its colorful orange foliage in the fall. There is also a cultivar that is fruitless, and that is Rotundiloba.
Root Problems and Fruit Litter
The sweet gum tree has a large, aggressive root system, and its roots can lift up curbs, sidewalks, patios or driveways. They should be planted at least 8 to 10 feet away from those areas to avoid any problems with their root structure. Fruit litter can also be a problem, not only for clean-up but for safety reasons. (Pedestrians can slip and fall when walking on the fruit.)
Sweet gum trees are susceptible to canker diseases. Canker diseases are serious as there are no chemical controls for the disease. Signs of canker disease are found on the trunk. You will notice sunken areas on the trunk, and possibly bleeding as well. The bark on the infected area will be brown and dead, as well as the sapwood. If the tree is only lightly infected, you can try pruning out the infected area. A severe case of canker disease will lead to death of the tree. The best defense against canker diseases is to maintain a healthy tree through a program of watering and fertilization. (Stress-free trees are able to withstand/fight off disease.)
Leaf Spots and Leader Dieback
Leaf spots are a common disease and are more unsightly than they are serious. Sweet gum is susceptible to various types of leaf spot. Spots appear on the leaves and eventually cause the leaves to fall off of the tree prematurely. You should rake up the diseased leaves and dispose of them; do not put them in your compost bin. Established sweet gum trees growing in the southern region of the United States are susceptible to leader dieback. Leader dieback is when the upper portion of the tree or leader dies. It is believed that this occurs due to a lack of moisture and/or construction injury as stated by the U.S. Department of Agriculture Forest Service.