The flowers of Aptosimum lineare var. lineare grow solitary from leaf axils near the base of the plant. The trumpet-shaped flower has a five-lobed calyx and no flower stalk to speak of.
The five spreading corolla lobes are velvety, royal-blue to bluish purple in their upper parts, (sometimes) with dark blue to black patches in the flower throat. The inside of the broadly cylindrical corolla tube is white. The hairy green anthers are included, out of sight in the tube. There are four stamens in two unequal pairs.
Flowering follows summer or early autumn rain (iNaturalist; JSTOR; www.zimbabweflora.co.zw).