New Zealand flax

Sun

Full sun to partial shade; foliage is usually strongest and most upright in good light.

Water

Water regularly while establishing. Established plants tolerate dry spells but grow better with occasional deep watering; avoid stagnant winter wet.

Soil

Adaptable to clay, loam or sandy soil, provided drainage is adequate. Moist but well-drained soil gives the best growth.

Height

6-10 ft (1.8-3 m) in leaf; flower stems can reach 12-15 ft (3.7-4.6 m)

Spread

6-10 ft (1.8-3 m)

Flowers

Summer: tall, branching stems carry tubular, dull red to reddish-brown flowers. Flowering can be irregular, especially in cool climates.

Foliage

Evergreen. Long, leathery, green to grey-green leaves with narrow reddish margins, held in upright or arching fans. Named cultivars may have bronze, purple or striped foliage and can be much smaller than the species.

Growth

Moderate; forms a substantial clump over several years.

Care needed

Low

• Water deeply during dry weather through the first growing season.
• Give established plants a deep soak during prolonged drought, especially in containers.
• Apply a light dressing of balanced fertiliser in spring if growth is weak; avoid heavy feeding.
• Mulch around the clump, keeping mulch clear of the leaf bases.
• In colder areas, choose a sheltered site and protect the crown during severe freezes; move containers to a bright, frost-free place where winters exceed its tolerance.

Pruning. In spring, cut dead, frost-damaged or badly split leaves individually at their base, wearing gloves. Remove spent flower stems at the base unless you want seed; do not shear across healthy leaves.

Early spring

Remove winter-damaged leaves once the risk of severe frost has passed.

Spring

Plant or divide clumps as growth starts, allowing room for their mature width.

Late spring

Refresh mulch and feed lightly if the plant is growing poorly.

Summer

Water new plants during dry spells and check leaf bases for mealybugs.

Late summer

Cut off fading flower stems before seeds ripen where unwanted seedlings are a concern.

Late autumn

Move vulnerable container plants under cover and check that pots and planting sites drain freely.

• Use a single clump as an architectural focal point in a generous gravel bed or courtyard.
• Combine with ornamental grasses and rounded shrubs to contrast upright leaves with softer shapes.
• Plant in coastal borders with salt-tolerant shrubs, leaving enough space for the broad clump.
• Place beside a pond for bold foliage and reflections, keeping the crown out of standing water.
• Use a large container on a terrace, choosing a genuinely compact cultivar where space is limited.

Garden styles it suits: Architectural minimal, Contemporary minimal, Coastal, Modern Mediterranean, Pacific Northwest woodland and Winter interest.

Plant it with: Agapanthus, Kōhūhū, Hebes, Lomandra, Japanese silver grass and Sea lavender.

Wildlife: The nectar-rich flowers feed birds in New Zealand, particularly tūī and bellbirds, and may attract nectar-feeding birds and insects elsewhere. Dense clumps provide shelter for small animals.

• Mealybugs can hide deep between leaf bases, leaving white waxy deposits. Inspect the fans, remove accessible colonies by hand and use a locally approved treatment if the infestation persists.
• Crown or root rot can develop in cold, poorly drained soil. Improve drainage, reduce watering and remove badly rotted plants.
• Hard frost can brown or collapse leaves. Leave damaged foliage until severe frosts have passed, then remove it; protect the crown during future cold spells.
• Leaf spots and streaks may disfigure foliage. Remove badly affected leaves, clear dead material from the clump and avoid overhead watering.

Not known to be toxic to cats, dogs, horses or people. No part is generally recognised as poisonous, but the tough, fibrous leaves are unsuitable to eat and may cause choking or digestive upset if swallowed; leaf edges can also cut skin.

Where it spreads. Reported invasive on Saint Helena and in the Azores. It has also escaped cultivation in coastal California and parts of Australia; local status varies. Remove seed stems near natural areas and check local weed guidance before planting.

• Mountain flax (Phormium cookianum)

  Usually has softer, more arching leaves and hanging, often twisted seed capsules; New Zealand flax generally has stiffer leaves and upright capsules. Garden hybrids can be difficult to identify.

• Cabbage tree (Cordyline australis)

  Develops a woody trunk topped with leaf rosettes and produces sprays of small, pale flowers; New Zealand flax keeps its leaves in basal fans.

• Spanish dagger (Yucca gloriosa)

  Has rigid leaves with sharp terminal spines and conspicuous creamy bell-shaped flowers; New Zealand flax lacks the hard terminal spine and has narrow tubular flowers.

Phormium comes from the Greek word for a basket and tenax means tough or tenacious, referring to the strong leaf fibres traditionally used by Māori for weaving and cordage.

Propagation. Divide established clumps in spring, keeping roots and several healthy leaf fans on each division. Sow ripe seed in spring for species plants; seedlings from named cultivars may not resemble the parent.

Accepted botanical name

Phormium tenax

In the US and Canada

Introduced in Hawaii.

Native range

Antipodean Is., Chatham Is., New Zealand North, New Zealand South and Norfolk Is..

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.