The flowers of Prenia sladeniana grow in clusters on branches that may become 40 cm long.

Prenia flowers have four or five fleshy green sepals. The petal and sepal bases are fused into a short tube. The white petals of P. sladeniana are thin, narrow and oblong, growing in two or three series. Some slight pink in the flowers may occur. Petal tips are rounded and may curve down somewhat.

A large cluster of filamentous staminodes, sterile stamens without anthers, surround the yellow-anthered stamens in the flower centre. There are four grooved nectar glands in the flower base.

Flowering happens from spring to mid-autumn after rain.

The fruit capsule has a funnel-shaped base and four deep locules. The valves open when wet, close when dry, releasing seed in chance batches when germination becomes likely.

Prenia seeds are black with rough, tuberculate surfaces (Le Roux, et al, 2005; Smith, et al, 1998; Herre, 1971; iNaturalist; http://llifle.com).