Bidens hillebrandiana ssp. hillebrandiana (kookoolau), is a short-lived perennial herb in the Asteraceae (sunflower) family, 20 to 30 cm (8 to 12 in) tall. Leaves rarely simple, usually pinnately or bipinnately compound, 3.5 to 8 cm (1 to 3 in) long including petiole, leaflets 3 to 9, fleshy, ovate, usually 5 to 25 mm (0.2 to 1 in) long, 2 to 15 mm (0.1 to 0.6 in) wide, glabrous or sparsely pubescent, margins crenately (rounded) toothed or lobed. Flower heads solitary or 1 to 3, sometimes 4, per inflorescence on stalks 2 to 8.5 cm (0.8 to 3.3 in) long in simple or compound cymes terminating main stem and lateral branches. Achenes gray to grayish black, straight, wingless, 6 to 8 mm (0.2 to 0.3 in) long, 0.8 to 1.2 mm (0.03 to 0.05 in) wide, and bristly.