The sweet gum tree is a medium sized tree that grows to a max height of 40m. It has very straight stems at almost 90-degree angles when it is a sapling. These branches will then turn upwards with age as the tree becomes fuller. The species is generally considered to be deciduous although occasionally, particularly in the southern part of its range, it may be semi-evergreen with little leaf fall. The bark is a grey-brown color. Once the tree gets to be about 25 years old, the bark becomes deeply ridged and fissured.

The leaves are arranged oppositely and have the star-like appearance as mentioned earlier. When they are crushed they release a pleasant sweet aroma. Some refer to the aroma as somewhat cinnamon-like, in combination with the sweet resin. Something interesting about the sweet gum leaves is that each twig produces two types of leaves. The first leaves to form in the early spring are relatively shallow lobed. The late leaves are more deeply lobed and generally have shorter petioles than the first leaves. In the fall, most of the leaves turn deep purple and add a unique tone to fall foliage. The pigment for this deep red/purple color is anthocyanin. This pigment hides under the green chlorophyll in the spring. In the fall when the weather cools down and the connections of the leaf stems to tree seal off, the purple color blazes through. Leaves that have less of the anthocyanin pigment and more carotenoid turn yellow and red adding to the warm hues of trees like the oak and maple.

The sweet gum is a monoecious tree, meaning it has both male and female reproductive parts. It has wind-pollinated flower production in mid-to-late spring and fruit production in late fall. One of the most distinguishing characteristics of the sweet gum tree would be the prickly round fruits it produces, which are held individually, rather than in bunches. They are popularly nicknamed a "space bug", "monkey ball", and “bommyknocker” because of its spiky appearance. The ball is about 1-2 inches in diameter and houses about 50 capsules. Each of these capsules contains 1-2 seeds. The fruits open to release wind-dispersed seeds, which are eaten by birds, squirrels, and chipmunks .