The leaves are under 2 metres in length while those of P. tenax range from 1 to 3 metres in length. The scape is much shorter than that of P. tenax, rising up to 2 metres in height while that of P. tenax is around 5 metres in height. The colour of the inner tepals is green while the outer tepals are yellow to red. In contrast the tepals of P. tenax are a dull red, with the tips of the inner tepals being less strongly recurved. The capsules of P. colensoi, unlike those of P. tenax are twisted and pendulous, and may be twice as long. Phormium colensoi has two distinct geographic forms, one occurring in lowland parts of the North Island, and the other in the southern and mountainous areas of the South Island as well as ranges in the North Island. The lowland form has green or yellow tepals and the mountain form has red tepals. In the Cook Strait area, both forms and intermediates can be found.
Taxonomy
The species was originally mentioned without description by William Colenso, the name being given as Phormium forsterianum. It was later known as P. colensoi, a name that was listed without description in 1846 by J. D. Hooker. The name became better known from J. D. Hooker's 1864 publication in Handbook of the New Zealand Flora. However, previously, in 1848, Auguste François Le Jolis had described the species under the name P. cookianum, and for many years this name was thought to have priority over Hooker's name P. colensoi. The latter is now regarded as the accepted name, based on a brief description of the species in a quotation from J.D. Hooker in an article by Auguste Le Jolis in the Revue Horticole of 1 January 1848. Another specimen, believed to be identical to a plant found by Ronald Gunn at the Whanganui River in 1864, was described from a plant growing in a garden in Torquay, England in 1888 and given the name P. hookeri. This name is also now regarded as a synonym of P. colensoi.
Cultivars
Numerous cultivars of this species have been selected for cultivation :-
'Black Adder'
'Cream Delight'
'Dark Delight' has deep-red leaves up to 1.2 metres in length
'Maori Maiden', an erect growing cultivar with leaves to 1 metre in length with bronze stripes
'Sundowner', a cultivar with very long leaves which are up to 1.8 metres long. These have a purple centre and cream edges.
'Tricolor', an upright cultivar that has leaves with red, yellow and green stripes. The flowers are pale yellowish-green.
There is also a dwarf cultivar, and hybrid cultivars have been selected from crosses with Phormium tenax. P. colensoi cultivars are regarded as less hardy than other Phormium cultivars.
Uses
Numerous traditional cultivars have been used by the Māori people for various purposes:
Wharariki - a variety from Urewera has a superior fibre quality that may be woven into a soft kete. It has a slight yellow colouration when dried. Another variety from Tairāwhiti is suitable for soft baskets, rorou and toys.
Whakaari - a variety with leaves suitable for weaving ketes, but less suitable than other cultivars for piupiu. The leaves have strong blades and dry naturally to a deep green colour, or to a pale greenish-fawn after being boiled for a minute.
