Pteralyxia kauaiensis, a member of the dogbane family (Apocynaceae), is a long-lived perennial tree 3 to 8 m (10 to 26 ft) tall. The leaves are dark green and shiny on the upper surfaces but pale and dull on the lower surfaces. They are generally egg-shaped and usually 11.0 to 22.0 cm (4.3 to 8.7 in) long and 40.0 to 65.0 mm (1.6 to 2.6 in) wide. The pale yellow flowers are trumpet-shaped, 8.0 to 12.0 mm (0.3 to 0.5 in) long, with each of the five lobes 3.0 to 4.0 mm (0.1 to 0.2 in) long. The paired fruits, of which usually only one matures, are drupe-like, bright red, and fleshy. The woody endocarp that encloses the single seed has two prominent central wings and two reduced lateral wings.