New Zealand Flax (Phormium)

How to choose a New Zealand flax

Size comes first, because flax varies from knee high to well above head height. Phormium tenax, the species, grows two to three metres tall with flower stalks higher again. The named garden forms are much smaller. The Sweet Mist New Zealand Flax is a dwarf bronze selection suited to borders and pots. The Phormium Bronze Baby is a long established compact bronze form with arching leaves, and the Bronze Warrior Flax is another bronze leaved variety.

For a darker accent there is the Black Rage Plant, and for a plain green clump that sets off coloured neighbours, the Green Mist New Zealand Flax. Check the mature height listed for each variety before deciding where it goes.

Where New Zealand flax grows

Flax does well in cool to warm temperate climates: Tasmania, Victoria, the southern tablelands, Adelaide, Perth and the coast up to about Sydney. It takes frost, strong wind and salt spray, and grows in most soils. In tropical and subtropical humidity it sulks: the crown is prone to rot in hot, wet summers, and plants often decline after a few years. North of Sydney, give it an open, airy position with sharp drainage, or choose another strappy plant.

Full sun gives the strongest leaf colour, though flax grows in part shade. It is a natural choice among coastal and salt tolerant plants, and it combines well with other grasses and strappy leaf plants. Compact forms are sound plants for pots.

The plain species can self seed in cool, wet districts. If you garden near bushland or a waterway, cut off the spent flower stalks before the seed ripens.

Planting and spacing

Plant in autumn or spring. Dig a hole twice the width of the pot, set the plant at the same depth it grew, and avoid burying the crown, where the leaves fan out. Space dwarf forms 40 to 60 centimetres apart for a mass planting, and medium forms about a metre apart. In heavy clay, raise the planting area so water drains away from the crown. Mulch, but keep it back from the base of the fan.

Care basics

Water regularly through the first summer. Established clumps are drought hardy in temperate areas, though coloured forms look fresher with an occasional deep soak.

Never shear a flax across the top. Cut leaves do not regrow from the cut, so the brown, blunt ends stay for years. Instead, remove old, split or dead leaves one at a time, cutting each as low as you can at the base of the fan with a sharp knife or secateurs. Do this once a year in late winter. Cut flower stalks off at the base after flowering. If a coloured variety sends up a plain green fan, remove it at the base before it takes over.

Common questions

How big does New Zealand flax grow?

It depends on the variety. The species reaches two to three metres, while dwarf selections stay well under a metre.

Can I cut flax back to the ground?

It is better not to. Remove individual old leaves at the base instead. A hard cut leaves a clump of blunt stubs that takes a long time to recover.

Does New Zealand flax grow in Queensland?

It is unreliable in coastal Queensland because of the summer humidity. It can do well in cooler, elevated districts with good drainage.

Will flax grow near the beach?

Yes. It tolerates salt wind and sandy soil, and is widely used in coastal gardens across southern Australia.