Phormium cookianum Black adder

The Phormium cookianum 'Black Adder' is a very beautiful architectural plant with a very dark fan-shaped silhouette. Its leaves are like large shiny ribbons, a purple so dark that it almost appears black depending on the lighting. They are gathered in an imposing tuft, with a very slightly trailing habit. This evergreen plant offers a particularly exotic aspect to the garden, throughout the year, including during its summer flowering with upright spikes adorned with nectar-rich tubular flowers. Whether planted alone or in a mass, this highly graphic plant, although not very hardy and preferring humid climates, is ideal for mild oceanic climates. It will also thrive in a large container, to be overwintered in a cool climate. 

The Phormium cookianum or mountain flax belongs to the agavaceae family, just like its cousin the Phormium tenax, both native to New Zealand. However, the former shows less growth, is slightly less hardy, and prefers cooler, fertile soils. The 'Black Adder' cultivar, born in 2009, has very dark foliage. This superb rhizomatous perennial grows in a large non-spreading clump. With an upright and arched habit, it reaches a height of about 1.2 meters depending on the growing conditions, with a spread of 1 to 1.2 meters (3 to 4 feet). The leaves are wide, slightly arched, very long, flexible, pointed, and pendulous at their tips. Their very dark purple-black color is enhanced by a shiny texture. Tall flower stalks, at least 1.7 meters (6 feet) high, appear from May to July, depending on the climate, towering above the foliage clump. They are green tinged with yellow and orange, arranged in curved flower spikes. They are followed by the formation of trailing spiralled fruits. This flowering attracts certain birds and numerous pollinating insects.

This Phormium is a plant of great ornamental value, suitable for large beds or large rockeries in mild climates. It may be disappointing in Mediterranean climates, but splendid on the oceanic side of our country. Whether used alone or planted in groups, it structures the space and adds a very exotic charm to the garden. Like tall grasses, it is a wonderful perennial for a modern garden with clean lines. In colder regions, it can be planted in a very large pot on the terrace or balcony, to admire its presence during the warm season, and overwintered frost-free in a cold greenhouse or a slightly heated conservatory. In an urban garden, it softens concrete structures. For a contrasting and exotic atmosphere, it can be paired, for example, 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', plants also from Oceania, perfect for coastal areas.

The Maoris use Phormiums like we use flax, for its fibers that are exploited in the textile industry. From this ability comes their vernacular name of 'New Zealand Flax' or 'Mountain Flax'.