Cyanea mannii, a member of the Campanulaceae (bellflower) family, is a branched shrub 1.5 to 3 m (5 to 10 ft) tall. The leaves are narrowly elliptic or lance-shaped, 12 to 21 cm (4.7 to 8.3 in) long and 2.5 to 5 cm (1 to 2 in) wide with hardened teeth along the leaf margins. Each flower cluster, arising from the axil of a leaf stalk 20 to 35 mm (0.8 to 1.4 in) long, comprises 6 to 12 flowers. Each flower has a smooth green fused calyx with triangular lobes. The purplish corolla forms a nearly upright tube 30 to 35 mm (1.2 to 1.4 in) long which ends in five spreading lobes. Berries are not described.