As the common name of summer impala lily indicates, the flowers of Adenium swazicum appear together with the leaves in summer, unlike those of its taller and more illustrious winter-flowering relative, A. multiflorum with its two-tone flowers.

A. swazicum plants offer a range of flower colours in shades of pink, rose-red and maroon. Five uniformly coloured petal lobes with rounded and sometimes slightly pointed tips spread broadly from the corolla mouth above the long and narrow corolla tube. The outer surfaces of the petals are often much darker than the inner ones, the dark colouring already present on the buds. Flowering happens from midsummer through autumn.

The fruits of A. swazicum are cylindrical follicles from which small seeds with hairy attachments are released, dispersed on the wind (Smith and Crouch, 2009; Onderstall, 1984).