Luma is an evergreen tree that measures up to 25 m (80 ft) tall and up to 50 cm (25 in) in diameter, with smooth bark, decorticant, reddish to brown.

New shoots are hairy, which distinguishes it from Amomyrtus meli, a species that it strongly resembles.

The flowers are hermaphroditic, with 5 fused sepals and 5 free white petals about 4 mm long.

The fruit is a black to purplish-black berry when mature, 1–1.5 cm in diameter, generally with 3 seeds, about 3–4.5 mm.

[2] The name Amomyrtus comes from the Greek Amos (fragrant) and the family name Myrtus, and Luma is the Mapuche name for the tree.