Hibiscadelphus stellatus is a small tree ranging in height from 3 to 6 meters, with trunks up to 30 cm in diameter. The bark is smooth, varying in color from light tan to gray, and the stems are many-branched. The young branchlets are densely covered with white to tan pubescent, 8–12-rayed stellate trichomes, giving the surface a scurfy-waxy appearance that becomes glabrescent with age. The leaves are simple and alternate, with blades broadly ovate to suborbicular or subreniform in outline, measuring 7.5 to 18 cm in length and 9.5 to 18 cm in width. The leaves are chartaceous, with an apex ranging from acute to obtuse or rounded and a cordate base featuring densely stellate-pubescent new growth. The flowers are solitary, axillary, and either erect or spreading, with pedicels densely covered in stellate pubescence similar to the petioles. The calyx is tubular-saccate, primarily 5-lobed, obscured by dense tan stellate pubescence. The corolla is zygomorphic (one plane of symmetry) and adaxially curved, presenting a unique coloration that transitions from purple, purple-green, or purple-yellow on the outer portion to yellow or purple-tinged distally on the inside. The stamens form a monadelphous column, with the style and staminal column’s apex exserted. The fruits are woody capsules, globose-cuboid to ovoid, measuring 2.5 to 4 cm in length and 2.2 to 3.3 cm in diameter, with a rough surface covered in dense tan stellate hair clusters. The seeds are reniform, 10 to 12 mm long, and covered in dense lanate yellowish-tan hairs. It occupies very steep, rocky slopes with a windward aspect, situated mid-slope between the upper rim of a deep valley and a perennial stream below, within lowland mesic forests characterized by a mosaic of trees and shrublands with an open canopy. This habitat, typical of volcanic, basaltic soils from the Wailuku Series of original shield-building flows, receives an average annual rainfall of 1200 to 1400 mm and is well-drained. It occurs at elevations of 800 to 900 meters.