Depending on climatic conditions, trees may be evergreen or deciduous. In forests it is a straight, slender tree, up to 18 m on forest margins, and in the open it is wider-spreading, sometimes drooping, and in the KwaZulu-Natal bushveld it often grows as a shrub approx. 1.5 m tall. The less water it receives, the shorter it is.

Trema bark is smooth and light grey with conspicuous lenticels (corky spots).

The leaves are simple, alternate, stipulate although the stipules drop early, and usually 3-nerved from the base. It is quite difficult to distinguish its leaves from those of Celtis africana (white stinkwood), but they are usually bigger and more elongated. The leaf base is frequently unequal. Leaves taper from the base to the apex, and vary from 60 to 150 mm long and 25 to 50 mm wide. Leaf margins are finely serrated, and the young leaves are rough and hairy, occasionally becoming smooth when old.

Flowers are small, inconspicuous and greenish, carried in short dense bunches. They are usually unisexual, i.e. male and female are separate, occasionally they are found together. Flowers appear irregularly from late winter to autumn.

Fruits are small, round and green, becoming black when ripe. They are carried on very short stalks - this is the easiest way to tell this tree apart from the white stinkwood whose stalks are up to 13 mm long.