Astelia menziesiana is a terrestrial or epiphytic, sub-acaulescent (having almost no stem), rhizomatous perennial herb. The leaves of this plant are simple and arranged in a 3-ranked manner. They are long, measuring 30 to 160 cm, and narrow, about 1 to 7 cm wide. The upper surfaces of the leaves are covered with scales that peel off in skin-like pieces as the leaf ages, often leaving old leaves completely bare, while the lower surfaces are densely covered with closely appressed scales. Beneath these scales, the leaves are densely woolly pubescent, but this pubescence tends to fall off with age, leaving some leaves essentially glabrous. The base of the leaves is densely white to brownish shaggy pubescent. The margins of the leaves are entire, with parallel, conspicuous veins and a sheathing formation. Stipules are absent. The flowers are on scapes (leafless stalks from roots) 10 to 120 cm long, usually densely shaggy pubescent. The staminate (male) flowers form racemes 3 to 20 cm long, pedicels 3 to 10 mm long, and bracts 4 to 11 mm long. The pistillate (female) flowers also form racemes 3 to 18 cm long, with shorter pedicels and bracts. The flowers are unisexual, and the plant is dioecious, meaning individual plants produce either male or female flowers. The tepals are variously colored – green, brownish maroon, or occasionally white – and can be densely pubescent or glabrous. The staminate flowers have six stamens with anthers 1 to 4.2 mm long, while the pistillate flowers have non-fertile anthers and a superior ovary 4 to 6 mm long. The fruit is an orange berry, sub-globose to ellipsoid, measuring 5 to 9 mm long and 4 to 6 mm in diameter. The seeds are black, irregularly ovoid to fusiform (spindle-shaped), and measure 1.7 to 2.5 mm long. It occurs in mesic to wet forests and bogs, typically at 610-2,230 meters.