Whether you're looking for a tropical touch or a dramatic focal point, tall, attractive Phormium makes a strong architectural statement in any garden. Although they'll grow taller than three metres under ideal conditions, in most Canadian gardens Phormium will likely not reach more than one metre by one metre (excluding flower spikes, which will be 60 to 90 centimetres higher) and are best treated as annuals.
Native to New Zealand, the two species of large, clumping plants are members of the Agavaceae family and have leathery, sword-like leaves in various shades of green, pink, cream, bronze and red, and are either striped or variegated. Although the species do produce blooms, they are primarily valued for the dramatic effect of their foliage, which grows in V-shaped fans from the base.
New Zealand flax (P. tenax), harakeke in Maori, is the larger and more common of the two species. It has long, strap-like leaves in shades of green, bronze and maroon, and orange-red flowers that bloom in July, reaching heights of up to four metres, and eventually developing into erect seed pods.
Mountain flax (P. cookianum), wharariki in Maori, grows to two metres tall in its native habitat, with narrow leaves that are arching rather than erect. Its flowers, which appear in midsummer, are greenish yellow.
In addition to hybrids, there are many cultivars of both species in a broad range of leaf colours from red to orange, yellow, pink and cream, as well as various combinations.
Excellent in the ground or in containers, Phormium like rich soil and need lots of moisture during their active growth cycles in late spring and summer. Considered hardy only in Zone 8 and higher, they grow best in full sun but will tolerate some shade. In summer, when mature, they produce panicles of flowers in orange-red or yellow-green that attract nectar-loving birds.
It's possible to overwinter Phormium outdoors in a sheltered spot, but most varieties are best brought indoors in winter and will do well in a cool room with a lot of light.
Phormium are propagated by division in spring. Healthy plants will soon grow into clumps as fans of new foliage develop around the older leaves. These will eventually send out their own roots, which can then be detached from the parent plant. To preserve most of the roots from the cutting, dig up the whole plant and divide it into several pieces using a sharp spade or knife.