Cyanea duvalliorum is a tree species growing 4–6 meters tall, notable for its distinctive juveniles that do not flower precociously. Juvenile stems are unbranched, about 0.7–1.2 cm in diameter, covered with numerous prickles, while adult stems are thicker, 1.6–2 cm in diameter, branching about a meter above the ground and becoming smoother at the apex. The leaves are simple and alternate, with juveniles featuring elliptic or oblanceolate blades, 13–27 cm long and 7–17 cm wide, whereas adults have larger, elliptic or oblanceolate blades, 31–53 cm long and 10–20 cm wide. Juvenile leaves are dark green, glabrous on the upper surfaces, and light green with prickles on the lower surfaces. Adult leaves are also dark green and glabrous on the upper surface but have pubescent veins on the light green lower surface. Leaf margins vary from pinnately divided in juveniles to pinnately parted or divided in adults. The flowers are arranged in racemes of 6–10, located below the leaf rosette, with a horizontal peduncle and rachis. The calyx is 5-lobed with narrowly oblong lobes, while the corolla is zygomorphic (bilaterally symmetric), white, and arcuate. The stamens are five in number, forming a pubescent filament tube with anthers that are coherent but separate post-anthesis. The fruits are bright orange, ellipsoid berries, 17–21 mm long, with numerous small, brown, ellipsoid seeds, ca. 0.7 mm long, with a smooth, shiny, straight, short to spatulate dicotyledonous embryo embedded in oily endosperm. It is found in mesic forests and grows at elevations of 855–1,522 meters.