How to grow phormium
All you need to know about growing phormium, or New Zealand flax, in our Grow Guide.
New Zealand Flax, or Phormium, is a handsome long-lived evergreen shrub that forms bold clumps of elongated sword-shaped leaves. The attractive, often colourful foliage looks good all-year round and makes the perfect foil for other plants in borders, raised beds, gravel gardens and pots. Leaf colour is extremely varied and includes olive-green, purple, yellow, cream, red and apricot variegations, in wide or fine stripes. Occasionally phormiums produce flower stems in summer, which are tall and branching with yellow-green, reddish or brown flowers. Plant height and leaf length varies considerably according to the variety of phormium you're growing, from as little as a metre up to several metres. Phormiums originate from New Zealand, where their tough fibrous leaves were traditionally used in weaving and basket making. Phormiums are moderately hardy once established, although not suitable for cold exposed sites.
How to grow phormiums
Plant phormiums in spring or early summer in a sunny spot in fertile well-drained soil. Keep moist during dry spells for the first growing season, but after that phormiums growing in the ground need little care, and pot-grown plants need only watering.
Growing phormium: jump links
- Planting phormium
- Caring for phormium
- Propagating phormiun
- Growing phormium: pests and problem-solving
- Phormium varieties to grow
Where to grow phormiums
Phormiums are suitable for a wide variety of situations around the garden, including coastal locations in milder parts of the country. Plant in beds and borders, on banks, as screen plants, and the smaller varieties are ideal for pots. Site phormiums in full sun. Cutting back phormiums to reduce their height isn’t possible without spoiling their attractive shape, so choosing the right variety for the site is especially important. Phormiums can survive winter temperatures down to around -5 to 10°C if given a sheltered site, although they’re not suited to areas that regularly suffer from long cold spells in winter.
How to plant phormiums
The ideal soil for phormiums is fertile and moisture-retentive yet well-drained. Dig in organic matter such as well-rotted garden compost or soil conditioner before planting, unless the soil is already in good condition. Dig a hole larger than the roots; remove the pot and unwind any congested roots, spreading them out in the planting hole. Plant so the top of the root ball is at ground level; backfill with excavated soil and firm in using the heel of your boot. Water well to settle the soil around the roots and keep moist during dry spells for the first growing season. To grow phormiums in pots, use a soil-based potting compost.
How to care for phormiums
Phormiums growing in the ground need little care once established. Mulch the soil annually with composted bark or garden compost to protect the roots from frost and improve the soil, and apply a general fertilizer every spring. Choose a fertilizer high in potash to encourage flowering.
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Water pot-grown phormiums regularly to keep the soil evenly moist but take care not to over-water. Feed each spring with a controlled release fertilizer, and pot on into a larger container if the roots are congested.
Keep phormiums looking smart by removing dead leaves and flower stems 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 to leave a short section that can be pulled off at a later date.
Mature phormiums can’t be pruned as this would spoil their shape but can be reduced in bulk by dividing up clumps.
How to propagate phormiums
Divide phormiums in spring, either by digging up and splitting plants that are several years old and have formed good-sized clumps, or if the phormium is too large to handle easily, by removing outer sections along with plenty of both leaves and 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.
Growing phormium: problem solving
Given the right growing conditions, phormiums are trouble-free. Mealy bug may occur at the base of leaves, particularly on older plants, but is usually controlled by birds. If over-exposed on very windy sites, the leaves can be damaged by wind, shredding at the tips, and then splitting. Waterlogged soil is liable to cause rotting and plants may die.
Advice on buying phormiums
- There are two main types of phormium – Phormium tenax and Phormium cookianum. Phormium tenax (and its cultivars) are quite compact and grow well in pots. Phormium cookianum is large and makes a huge statement in the garden
- While phormiums are readily available from garden centres, you may find more choice at specialist nursery
- Always choose healthy and robust plants, checking them over for signs of pests, damage and disease
Where to buy phormium
Phormium varieties to grow
- 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