Aulu trees are somewhat shorter than the soapberry (Sapindus saponaria), reaching heights of about 15m tall.
Aulu leaves are simple and elliptical, 7.5-27 x 3-14.5 cm. The silky brown flowers are single sexed, with both sexes occurring on the same tree. The flowers are produced in panicles up to 10-20 cm long. Aulu fruits are brown to black and round when ripe, about 2-3 cm in diameter. The single large seed is 1.2-2 cm long and dark brown.
(Staples, G. W. and D. R. Herbst. 2005. A Tropical Garden Flora: Plants cultivated in the Hawaiian Islands and other tropical places. Bishop Museum Press, Honolulu, Hawai`i.)
(Wagner, W. L., D. R. Herbst, and S. H. Sohmer. 1990. Manual of the flowering plants of Hawai'i, Bishop Museum Press, Honolulu, Hawai`i)