Phormium cookianum subsp. hookeri Tricolor

Phormium cookianum 'Tricolor' is a variety of Mountain Flax that is large and beautifully coloured, but also one of the hardiest and easiest to grow, in moist soil. This perennial, with its giant grass-like shape, forms a large erect tuft composed of large, persistent, prickly leaves that are green with cream margins and edged in pink-red. It is ornamental all year round, including during summer, with large panicles of green-yellow tubular flowers. It is both very bright and very impressive in a mass planting or in a large container on the terrace. This phormium appreciates moist soil in summer, drier in winter.

Phormium cookianum or Mountain Flax belongs to the agave family, just like its cousin the Phormium tenax, and both are native to New Zealand. However, the former is smaller and slightly less hardy, and prefers moister, fertile soil. The 'Tricolor' cultivar is a robust variegated foliage form. This robust rhizomatous perennial grows in a large non-spreading clump. Its growth is rather slow, reaching maturity at around 8 years. It has an upright and arching habit, reaching an average height of 1.5 meters (4 feet 11 inches) depending on growing conditions, with a spread of 2 metres (6 feet 7 inches). The leaves are wide, up to 10 cm (3.9 in), slightly arching, very long, flexible, pointed, and trailing at their tips. They are striped with bright green and creamy yellow, finely edged with purple-red. The quite spectacular flowering takes place in June-July. It takes the form of flower stalks at least 3 metres (9 feet 10 inches) high overhanging the foliage clump. The tubular flowers are yellow, tinged with green.

This Phormium is a plant of great ornamental value, suitable for large beds or large rockeries, in mild climates. It may sometimes be disappointing in hot climates if it does not receive regular watering in summer. Used as a specimen or planted in groups, it structures the space like large grasses. It is also a wonderful perennial for a modern garden with clean lines. In cold regions, it can be planted in a very large pot on the terrace or balcony, to admire its presence in the summer and overwinter it frost-free in a cold greenhouse or a slightly heated conservatory. In an urban garden, it softens concrete structures. For an exotic atmosphere, it can be associated with Leptospermum scoparium, a pink to red ball-shaped flower in summer, Helichrysum rosmarinifolium 'Silver Jubilee', Pittosporum tenuifolium Tom Thumb, or even Olearia macrodonta 'Major', also from the coast.

The Maoris use Phormiums as we use flax, for their fibres that are used in the textile industry. This ability probably gave them the vernacular name 'New Zealand Flax' or 'Mountain Flax'.