Cyanea solanacea is a shrub that grows 2–5 meters tall with muricate to aculeate branched stems, which are densely covered in juveniles. The leaves are simple and alternate with dimorphic blades; juvenile leaves are pinnately cleft to divided, measuring 20–40 cm long and 6–13 cm wide, with 9–13 segments per side that are oblong, oblanceolate, or triangular. Adult leaves are elliptic to oblanceolate or obovate, 16–36 cm long and 4–14 cm wide, with an acuminate or acute apex and cuneate base. Juvenile leaves have green, papillose to aculeate upper surfaces and pale green, pubescent, and muricate to aculeate lower surfaces. Adult leaves have green, glabrous, or papillose upper surfaces and pale green, pubescent lower surfaces. The margins vary from irregularly lobed to divided in juveniles to irregularly callose–dentate, lobed, or cleft in adults. The inflorescence comprises 5–10–flowers with peduncles 20–50 mm long and pedicels 8–12 mm long. The flowers are bisexual and perfect, with an oblong to obconical hypanthium 8–10 mm long and 3–4 mm wide, which can be glabrous, pubescent, or muricate. The calyx lobes are oblong or ovate, 4–15 mm long and 3–6 mm wide, with an obtuse to truncate or emarginate apex. The corolla is white-tinged with pale lilac, 48–60 mm long and 4–5 mm wide, pubescent or rarely subglabrous, and the tube is suberect to gently curved. The staminal column is pubescent, and the anthers, especially the lower two, have apical tufts of white hairs. The fruit is an orange, ellipsoid berry, 11–16 mm long, topped with persistent calyx lobes, and produces numerous seeds. It is found in the wet forests of Moloka’i and possibly West Maui at elevations of 1,080–1,190 meters.