Hibiscus arnottianus is a shrub or small tree generally 8 meters in height, though a few individuals will grow to 10 meters tall.
The leaves are mostly oval with a smooth upper surface and a lower surface with many to no hairs. Leaf margins or edges are smooth or have spreading pointed teeth near the leaf tip. The leaves are 4 to 10 centimeters long and often have red veins and stems. The faintly fragrant flowers have white petals 5 to 13 cm long with the tube-like green calyx being 2 to 3 centimeters long. Anthers are arranged along the upper third of the pinkish to dark red staminal column 8 to 19 cm long. Older flowers may be slightly pink to pale pink. In cultivation, Hibiscus arnottianus blooms almost continuously.
(Wagner,W.L.,Herbst,D.R.,Sohmer,S.H. 1999. Manual of Flowering Plants of Hawai'i.; Criley, R. 1998. 1999; Koob, G. 1998; Rauch. 1997)