The pink, white or bicoloured flowers of Hallianthus planus grow solitary or in groups of up to three from stem-tips or the leaf axils near them.

The about two whorls of petals spread in sunlight. Numerous, erect or curving, filamentous staminodes with coloured tips surround the stamens in the flower centre, not compressed into a cone. The nectary in the flower base is an uneven ring. Seeds grow on the outer wall of the ovary.

Flowering happens in autumn and winter (Williamson, 2010; Leistner, (Ed.), 2000; Smith, et al, 1998; iNaturalist).