Plant in full sun to shade. It can tolerate fairly dry conditions (coastal) but looks best with occasional to regular irrigation. Hardy to 15-20° F and possibly root hardy below these temperatures but does suffer severe foliage damage unless protected. This is a very nice large understory shade plant, and its flowers and seed pods are useful in large flower arrangements. In our garden is even grows well under the heavy shade of a large Citrus Tree. This plant is relatively pest free except for harboring snails that can damage new leaves and mealybugs. Though this straight species is durable enough to thrive if infested with the New Zealand Flax Mealybug (Balanococcus diminutus), this pest is particularly damaging to some of the weaker growing hybrids.

Phormium cookianum is less common than the other species of New Zealand Flax, Phormium tenax and has two distinct forms originating in different locations with one from the lower elevations of the North Island and the other from the more mountainous regions in the North and South Island with natural intermediates found between them. The genus was first described by the German naturalists Johann Reinhold Forster and his son Georg in 1775 from specimens they and the Swedish naturalist Anders Erikson Sparrman collected of Phormium tenax while on the second expedition aboard the Resolution with Captain James Cook from 1772 to 1775. The name Phormium comes from Ancient Greek word 'phormion' or 'phormos' meaning "mat," "basket," or "frail" (a wicker basket for dried fruit) in reference to the fibrous, plaited, or woven nature of mats and baskets the Maori people often made from the leaves of the plant. The specific epithet honors the British explorer Captain James Cook. Long called New Zealand Flax by the English and Harakeke by the Maori, by the settlers in New Zealand it is usually just called Flax.

This species was originally mentioned without a proper description by William Colenso in a letter he sent in 1844 to Sir William Jackson Hooker, the English botanist, botanical illustrator and the first director of the Royal Botanic Gardens, Kew. Colenso then called this plant Phormium forsterianum and later, in 1846 it was given the name Phormium colensoi to honor him by William's son Joseph Dalton Hooker, who became the second director of Kew. Though this name was listed without a proper description, it became better known from its listing as such in Joseph Hooker's Handbook of the New Zealand Flora, published in 1864. However, in 1848 the French merchant, judge and botanist Auguste François Le Jolis had described the species as Phormium cookianum and for many years this name has been thought to have priority over Hooker's name Phormium colensoi and this naming confusion has persisted ever since. The Royal Botanic Gardens, Kew does currently list Phormium colensoi as the currently accepted name but since we long grew this plant as Phormium cookianum, we continue to list it under this name. This is the parent species that gives the arch to many of the hybrid New Zealand Flax varieties. For more information on the history of cultivation of New Zealand Flax and the story of our introduction of the cultivars in the US, see our New Zealand Flax Page. 

The information displayed on this page about Phormium cookianum is based on our research conducted about this plant from books in our nursery library as well as from information that is provided by reliable online resources. We also have included our own observations made about it as it grew in the nursery gardens and other gardens visited, as well how the crops of this plant performed in the containers when we had them in our nursery field. We also include comments received from others and welcome hearing from anyone who has information about this plant, particularly if it includes cultural information aiding others to better grow it.