The flowers of Lobostemon marlothii grow stalked from leaf axils near stem-tips. There are leafy bracts below the five-lobed calyces.
The five corolla lobes are nearly equal, round-tipped and curving out slightly, more in the lower ones. The funnel-shaped corolla throats are pinkish red low down, as are the closed, club-shaped buds, partly sepal-covered. The sky-blue upper petal parts have white central lines from the base, abruptly ending where the outcurving begins in some.
The filaments are white and fleshy, curving near their tips. The small anthers are short and dark or partly so.
Flowering happens mostly in the latter half of spring (Vlok and Schutte-Vlok, 2015; Moriarty, 1997; Bond and Goldblatt, 1984; iNaturalist).