The simple, opposite leaves of Lippia rehmannii are short-stalked and lance-shaped, round-based ending in pointed tips. In the photo of a stem-tip the blades are fairly flat, while lateral margins may curve up, and the blades either slightly curving down to their tips or straight. The leaves are rough from sunken venation on their upper surfaces, consisting of midribs, ascending and incurving lateral veins, as well as finer net-veining. The blades are said to be hairy, particularly along the veins, but this is not evident in the photo. The leaf margins are finely toothed.
The small, white flowers grow in compact, conical, head-like spikes from leaf axils on faintly hairy peduncles that are up to 5 cm long. Each tiny, spreading corolla is two-lipped and round-lobed. There are four stamens in two unequal pairs in a flower, visible in the small but open corolla mouth.
In picture only few first flowers at the bottom edges of the spikes have opened yet. From below each bud in the compact head arrangement a pointed pale green bract covers or partly covers its bud (Germishuizen and Clarke, 2003; Leistner, (Ed.), 2000; Van Wyk and Malan, 1997; iNaturalist).