Phormium tenax has stiff parallel sided leaves, up to 9 ft (2.7 m) long and 2–5 in (5–13 cm) wide. The flowers are usually dark red and are borne on spikes up to 15 ft (5 m) high. Hardy in the UK.
Phormium tenax is found from coast to lower mountain areas, in swamps or hillsides, throughout the North and South Islands of New Zealand. It is known as New Zealand flax, although it is not related to the true flax, Linum. Many forms are in cultivation, and some are hybrids with Phormium cookianum.