Cyanea undulata is an unbranched (or the stem is occasionally forked) short-lived perennial shrub or subshrub 1.8 to 3.6 m (5.9 to 11.8 ft) tall with narrowly elliptic leaves 28 to 36 cm (11 to 14 in) long and 3 to 5 cm (1.2 to 2 in) wide, with wavy margins, a smooth upper surface, and fine rust-colored hairs covering the lower surface. The petiole (leaf stem) may be winged. The inflorescence is unbranched, 8 to 45 cm (3 to 17 in) long, and bears five to six flowers that are slightly curved, hairy, and yellowish. The fruit is a yellow berry about 1.7 cm (0.7 in) long.