The flowers of Xenostegia tridentata subsp. angustifolia grow solitary or in clusters of up to three on long, often reddish stalks from leaf axils. The flower stalks may be as long as 6 cm. The oblong sepal lobes are unequal and acutely pointed.

The erect flower has a funnel-shaped tube, the joined corolla lobes widen in trumpet-shape to a diameter slightly over 2 cm. The corolla is lemon-yellow, sometimes with a maroon eye in the corolla base. The stigma is presented well above the pale yellow anthers. Flowering happens from spring to autumn.

An ovoid, four-valved fruit is produced, about 1 cm long (Pooley, 1998; iNaturalist; www.zambiaflora.com).