Phormiums are exotic-looking long-lived evergreen perennials, that look good all year-round. Originally from New Zealand, hence their common name, New Zeland Flax, they were grown as a source of fibre for traditional Maori textiles, basket weaving and rope making.
They offer striking, often highly-coloured sword-like leaves ranging in colour from yellow-green to bronze-purple. The leaves are often striped or edged with cream, yellow, pink or red. Mature clumps produce tall stems with curious-looking yellow-green or red flowers that rise above the foliage in summer. Best grown in sunny borders and gravel gardens, they make great focal points in containers, but they’re not suitable for cold, exposed sites.
They are happy in most free-draining soils in a sheltered position in full sun. Phormiums may be slow to establish in very light, dry soils although they are drought tolerant once established. On wet soils, the roots can suffer and you should protect the base with a layer of bark or other dry mulch in the winter months which should be removed in spring.
The leaves can also be severely damage by hard frost, so less hardy types can be wrapped in garden fleece when cold weather is forecast. However, they’re not palatable to deer and rabbits, so you’re unlikely to have the leaves of your favourite Phormium nibbled by Peter Rabbit or Bambi!
You can consider Phormium as two types:
Compact varieties, which grow to around 1.2-1.5m (4-5ft) tall. The height will be influenced by the growing conditions. Plants grown in moister, fertile soil are likely to grow taller. These grow well in pots.
Taller varieties can be very large and make a huge statement in the garden. These will grow typically around 1.5-2.1m (5-7ft) depending on the cultivar and growing conditions. Some such as Phormium tenax can grow well over 2.4m (8ft) tall.
So what makes Phormium the plant of the month in May? Well, although mature plants can’t be pruned (this would ruin their shape), they can be divided, and late spring is the time to do it!
To reduce the size of your Phormium, either dig it up and split a plant that is several years old and has formed good-sized clumps, or if it is too large to handle easily, removing the outer shoots from the side of the main V-shaped leaf along with plenty of roots.
Replant or pot up the divisions at the same depth they were growing previously. As the new divisions can be top-heavy, stake and tie for their first year until the roots have become established.
To maintain your plant, you should remove any dead or damaged leaves from the base two or three times a year. Firmly pull leaves that are completely dead, to separate them from the plant and avoid a build-up of dead growth. If they won’t detach easily, cut them to leave a short section that can be pulled off at a later date.
If you’d like to introduce a Phormium to a sunny, sheltered spot in your garden, Gardener’s World recommends these varieties:
Phormium cookianum has light green leaves, and sometimes bears stems of yellow-green flowers. Height x Spread: 2m x 2m
Phormium tenax is larger and more vigorous, with plain dark green leaves that have blue-green undersides. It sometimes produces tall stems with reddish flowers. H x S: 3m x 2m
Phormium ‘Chocomint’ has green leaves with a broad central chocolate-brown stripe and is compact growing. H x S: 1m x 1m
Phormium ‘Jester’ is compact-growing with striped with apricot-pink and light green leaves. H x S: 1m x 1m
Phormium ‘Maori Queen’ has bronze-green leaves, brightly edged with red and a hint of cream. Sometimes sold as ‘Rainbow Queen’. H x S: 1m x 1.2m
Phormium ‘Platt’s Black’ has dark purple, almost black foliage and a very compact habit. H x S: 60cm x 90cm
Phormium ‘Tricolor’ has light green leaves boldly edged with cream and red. H x S: 1.5m x 1.5m
Phormium ‘Yellow Wave’ is a vigorous phormium, with large leaves striped with light green and yellow, brighter in the spring and maturing to yellow-green in summer. Tall stems of red-brown flowers are often borne, in summer. H x S: 2m x 2m
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