The simple, alternate leaves of Cullumia aculeata are sessile, their stem attachments extending below the leaves, while the blades ascend up the stems.
The leaf-shape is oblong to oblanceolate, the margins rolled under. A few thin, marginal spines are present. The dark-green, initially soft and later leathery blade surfaces are cobwebby when young, losing the hairy covering with age. The leaf midribs in picture are conspicuously white in the lower blade halves.
Leaf dimensions are 3 cm long and 1,5 cm wide (Vlok and Schutte-Vlok, 2015; Moriarty, 1997; Bond and Goldblatt, 1984; iNaturalist; www.worldfloraonline.org).