Melicope hiiakae, a member of the Rutaceae (rue) family, is a small tree 2 to 7 m (6.6 to 23 ft) tall, new growth with densely white to pale brown hairs, becoming smooth. The opposite leaves are glossy, thin, leathery, and elliptic to obovate, 4 to 20 cm (1.6 to 8 in) long and 2 to 9 cm (0.8 to 3.5 in) wide. Five to 15 separate finely haired male or female flowers occur in cymes arising between the stem and leaf or branch. Capsules (fruit composed of two or more carpels) are dark green, with fine hairs, 6 to 7 mm (0.2 to 0.3 in) long, 11 to 20 mm (0.4 to 0.8 in) wide, with 1 to 2 seeds per carpel.