Cyanea solenocalyx is a palm-like tree ranging from 1 to 4 meters tall. The stems are either unarmed or muricate, with juveniles presenting aculeate features. The leaves are simple and alternate, with dimorphic blades: juvenile leaves are ovate to broadly elliptic, measuring 8–30 cm long and 6–18 cm wide; adult leaves are oblong to obovate, ranging from 25–60 cm long and 9–20 cm wide. Juvenile leaves have an acute to acuminate apex and a rounded to truncate or subcordate base, with pubescent and muricate to aculeate surfaces. Adult leaves have an acute to obtuse apex and a cuneate to rounded base, with glabrous upper surfaces and pubescent lower surfaces, sometimes muricate along the midrib. Juvenile leaves have irregularly lobed or cleft margins, while adult leaves have callose-denticulate margins, sometimes shallowly lobed. Juvenile petioles are 3.5–11 cm long and muricate to aculeate, whereas adult petioles are 8.5–16 cm long and muricate. The inflorescence comprises 5–10 flowers, with peduncles 30–50 mm long and pedicels 12–24 mm long. The flowers are bisexual and perfect, with an obconical hypanthium 10–15 mm long and 5–10 mm wide at the apex. The calyx lobes are oblong to narrowly oblong, 15–30 mm long and 5–8 mm wide, connate at the base or distinct and narrower, or ovate and shorter. The corolla ranges from white with a median purple stripe to heavily purple-suffused, 34–45 mm long and 5–10 mm wide, with a suberect tube and erect lobes about a quarter the length of the tube. The staminal column is glabrous, with anthers and apical white hairs on the lower two. The ovary is inferior and 2-celled, with a 2-lobed stigma that becomes receptive after the pollen is expelled. The fruits are yellow to yellowish orange, ovoid berries, 16–18 mm long, containing numerous seeds. It is found in the wet forests of eastern Moloka’i at elevations of 900–1,390 meters.