large myrtle

Hypocalymma puniceum is a spreading shrub that typically grows up to 0.1–1 m (3.9 in – 3 ft 3.4 in), high and wide, its young stems four ridged to slightly four-winged. Its leaves are arranged in opposite pairs, linear, 8–16 mm (0.31–0.63 in) long and 0.5–1.1 mm (0.020–0.043 in) wide and sessile or on a petiole up to 1 mm (0.039 in) long. The leaves have 15 to 25 oil glands in two rows. The flowers are mostly borne singly in up to five leaf axils on a peduncle 4–6 mm (0.16–0.24 in) long with bracteoles 1.5–3 mm (0.059–0.118 in) long. The sepal lobes are egg-shaped to almost round, 2.5–3.5 mm (0.098–0.138 in) long and 3.0–4.5 mm (0.12–0.18 in) wide. The petals are bright pink, 8–13 mm (0.31–0.51 in) long and there are 35 to 55 stamens in two rows, the longest filaments 3.5–5 mm (0.14–0.20 in) long and joined at the base. Flowering occurs throughout the year, with a peak in the summer months, and the fruit is 2.5–3.5 mm (0.098–0.138 in) long and 3.5–4.5 mm (0.14–0.18 in) wide.

This species of Hypocalymma is found from Ballidu to near Lake Grace in the Avon Wheatbelt and Mallee bioregions of south-western Western Australia, where it grows in lateritic sand or gravel in mallee shrubland, shrubland or heath.