Schiedea diffusa subsp. macraei is a reclining or weakly climbing vine, woody at the base. Stems are 3 to 6 m (10 to 20 ft) long, with internodes near the inflorescence. Leaves are opposite, one-nerved without parallel nerves. Leaf blades are 6.5 to 9 cm (0.4 to 3.5 in) long, 1.5 to 2.5 cm (0.6 to 1 in) wide, lanceolate to narrowly ovate or sometimes oblong-elliptic; petioles 0.4 to 1 cm (0.2 to 0.4 in) long. Inflorescence is l0 to 50 cm (4 to 20 in) long with 65 to 73 flowers, yellowish green stalks 14 to 24 mm (0.6 to 1 in) long at anthesis, elongating slightly in fruit. Purple-tinged flowers do not open and self-pollinate. Sepals are purple, inner ones tinged green Seed capsules 4.5 to 5 mm (0.17 to 0.2 in) long, ovoid-globose, with numerous 1 mm (0.04 in) long seeds, and have been observed germinating in capsules while still attached to the plant.