named after the Rev. William Colenso FRS 1886, FLS 1865 (born 17 November 1811 - died Napier New Zealand 10 February 1899) printer to the Missionary Society who helped J D Hooker with his flora of New Zealand). Not to be confused with the Bishop of Natal John William Colenso (1814-1883).

Apprenticed to a printer; printer to the British and Foreign Bible Society; sent by the Society to New Zealand (1834)and remained there for the rest of his life; established the first printing press in New Zealand; printed the New Testament in the Maori language; became a missionary; ordained to serve a church in Napier; travelled throughout New Zealand; MP for Napier (1861); Honorary Secretary, Hawkes' Bay Philosophical Institute (by 1883); died as a result of a carriage accident Author of numerous Memoirs on the Botany & Zoology of New Zealand, & on the history, language, manners, & Customs of its native race, - published in the London Journal of Botany, Tasmanian Journal of Science & Transactions of the New Zealand Institute; Mr Colenso's labours as a Naturalist, Philologist & Ethnologist in New Zealand commenced half a centuary ago and have continued ever since - He was the first to record the discovery of the Dinornis [an extinct giant Moa over 3 metres tall) remains & he has contributed largely to a knowledge of the Flora & Fauna of the Islands.

P. colensoi(previously P. tenax) has been used in traditional Maori medicine. Flax-gum for healing wounds, chafed areas (Wall, Cranwell 1943). Rhizome, leaf base: - poultice for boils. Decoction used for intestinal worms, constipation. Mixed with juice of kōhia berry, taken internally for flatulence (J. White).

Previously identified as Phormium tenax, a visitor recognised it by its yellow green flowers and pendulous twisted seed pods as being Phormium cookianum. Phormium tenax has red flowers and upright seed pods. However Kew have recently changed the name on the basis of priority to Phormium colensoi (named after the Rev. William Colenso printer to the Missionary Society who helped J D Hooker with his flora of New Zealand) as this name was validly published (but overlooked) on January 1 1848, and it was only given the name Phormium cookianum (named for Captain Cook) a few months later in the same year. Ours appears to be the lowland form from North Island with yellow-green tepals whereas the mountain form from South Island has red tepals