These trees can grow to be very old, some specimens found in the United States believed to have started in the late 1300’s. Though the Blackgum grows to be centuries old, they are surprisingly small for their age. There is a 700-year-old champion that is just over 30 inches in diameter and about 60 feet tall -- smaller than a 100-year-old white pine. While white pine grow so rapidly that they eventually keel over in high winds, Blackgum grow relatively low to the ground and sticks around for centuries.
Living in zones 4B to 9, the Blackgum is native from east Texas to the east coast and up to central Michigan and Maine. It can grow on moist sites along streams and in the uplands, but it grows best on well drained, light-textured soils. It is tolerant of shade, and seems to grow more with the oak types than with the maples. The Blackgum's unusual root system, similar to a multiple taproot, probably explains why the tree does better in deep, moist soils.
Blackgum usually grows to a height of 50 to 75 feet although in rare situations it can grow to almost 150 feet high. It is most often less than 25 feet across. It should be spaced about thirty feet from other trees of similar growth patterns. It has a single, straight trunk with branches that emerge at right angles like those of pine trees. Young trees are often pyramidal, like a pin oak, while older trees may be more columnar or round-headed. The ends of the branches often droop, giving the tree a distinctive winter silhouette. Tkhe bark is dark gray with rectangular fissures that give a blocky appearance.
The branches are alternate with simple 5 inch long leaves that are shiny green above and paler and hairy underneath. One of the most outstanding attributes of the Blackgum is its glossy, brilliant red leaf color in the early fall. The leaves are oval shaped and are thin enough to let light shine through so that the tree appears to glow red as if it is lighted. In the fall it is generally the first tree to turn red, but it does it slowly over a six-week period. In the beginning, only a few leaves turn a bright red, but by early October, the tree is a landscape standout.
Blackgum flowers are borne singly or in clusters high in the branches. In the Midwest they bloom during May and June. The minute, greenish-white flowers may be perfect (containing both sexes), or staminate and pistillate flowers may be borne separately on different trees. While the female trees show their flowers, the male trees are producing pollen in large quantities. This pollen unfortunately can be very irritating to anyone with serious allergy problems. The problem disappears as soon as the flowers are gone.
The flowers are followed in the fall by blue-black berries about the size of a peanut. The berries are edible, but if you eat one, you will quickly learn why it is called a the tree is sometimes call Sourgum. These fruits may be considered a litter nuisance in urban/suburban plantings but are quite popular with many birds and mammals, and they wash away quickly without staining.