The affinity is with L. myrtoides from which it differs in the calyx-lobes being more united and the petals less united. In this and other species of the genus Lonchostoma the ovary is incompletely bilocular; the loculi being incompletely closed on the adaxial face. This is best seen on separating the loculi.
Like B. pentandra but leaves leathery, flowers pink to purple, petals fused for up to one-quarter their length, style ± 6 mm, longer than petal tube.
Usually 60-90 cm high, much branched. Branchlets villous. Leaves mostly 6-7 mm long, erect-spreading or ascending, obovate or oblanceolate, subacute, obtuse or acute, rounded-convex and villous beneath, becoming glabrous, deeply concave and glabrous above. Flowers in the axils of very slightly reduced leaves, in rotund inflorescences about 1 cm wide. Bracteoles 2-5 mm long, oblong-lanceolate, subacute, navicular, villous and minutely ciliate on the upper half of the dorsal face. Calyx 3-3.5 mm long, entirely free from the ovary: tube about 2 mm long: calyx-lobes ovate-deltoid, subacute or obtuse, ciliate, glabrous elsewhere. Corolla about 9 mm long, glabrous, purple: petals connate in a tube 1-2 mm long (occasionally apparently free); the free portion linear in the lower half, thence gradually widening into an obovate obtuse lamina. Stamens adnate to the lower margins of the petals, reaching to shortly above the middle: anthers 1-5 mm long, oblong: thecae free in the lower half. Ovary entirely superior, obovate-oblong, glabrous on the lower half, villous on the upper, imperfectly bilocular, with 1 or 2 ovules in each chamber: styles free, very slender, reaching to the anthers. Fruit obovate, apparently 2-seeded, dehiscent.