New Zealand Flax Plant Profile

Variegated New Zealand flax (Phormium) 'Yellow Wave' in stone planter, September
Ron Evans / Getty Images

Gardeners grow New Zealand flax (Phorium tenex) as a large and often colorful, spiky plant that makes an arresting focal point in the garden or in containers. It has sword-like leaves that shoot up from the base of the plant. New cultivars and hybrids are now available with leaves in bright shades of yellow, pink, red and bronze.

These blade-leafed, evergreen perennials are often used as specimen plants. Some are small enough to use in containers, others can reach several feet in diameter and grow to over 7 feet tall. On mature plants, the flower stalks shoot up above the leaves and produce curving, tubular red or yellow blossoms that are very high in nectar and a hummingbird favorite. Seed pods form after the flowers bloom. The seed pods are attractive in their own right, but you should deadhead them if self-seeding is not desired.

Phormium tenex got the name New Zealand flax because the Maoris of New Zealand actually used it for making a type of linen clothing, similar to flax, as well as for ropes and baskets.

As with most perennials, spring is the traditional time to plant New Zealand flax. If you are dividing or transplanting, make sure to do this before the plant begins to send up new growth shoots in the spring. New Zealand flax is a rather slow-growing species that can take several years before small seedlings mature into full-sized plants.

Botanical Name Phormium tenax (P. colensoi is a second parent to some hybrids)
Common Name New Zealand flax
Plant Type Herbaceous perennial
Mature Size 1 to 6 feet tall; 1- to 3-foot spread
Sun Exposure Full sun to part shade
Soil Type Average, well-drained soil
Soil pH 5.5 to 6.5 (acidic)
Bloom Time Rarely flowers; grown mostly for foliage
Flower Color Red
Hardiness Zones 9 to 11; often grown as a potted plant
Native Area New Zealand, Norfolk Island

How to Grow New Zealand Flax

New Zealand flax prefers a rich, moist soil and a location sheltered from harsh winds, but once established, the plants really aren’t fussy about conditions. This plant is grown mostly for its foliage, but it does send up a nice flower stalk with red or yellow flowers in mid-summer.

The mature size of your New Zealand flax plant will depend on the variety and your growing conditions. Many plants in containers grow 1 to 4 ft. tall, but Phormium tenax can reach 10 feet under ideal conditions.

It is very common to grow these plants in large containers, moving them indoors for the winter in colder climates. In the spring, they need to be gradually reacclimated before moving them back outdoors permanently for the summer.

Light

New Zealand flax prefers a full-sun to part-shade location, but since it is normally grown for its foliage, full sun is not crucial. In fact, in hotter climates, hybrids may do better with afternoon shade, since the leaf colors are often enhanced.

Soil

New Zealand flax is not fussy about soil; it will do well even in poor soil, provided it is well-drained. It prefers slightly acidic soil but is perfectly happy in neutral soil. When grown in containers, a rich potting mix is preferred over a standard potting mix.

Water

New Zealand flax has average water needs. When planted in the garden, about 1 inch of water per week in the form of rainfall and/or irrigation is ideal. Potted plants should be kept consistently moist, but not soggy.

Temperature and Humidity

New Zealand flax is dependably hardy and evergreen in USDA zones 9 to 11, but gardeners in zones 7 and 8 may find that the plants return each spring after dying back if they are heavily mulched for the winter. More often, cold-weather gardeners grow them as potted plants that are moved to shelter for the winter.

Fertilizer

These plants tolerate poor soil and thus don't usually require much in the way of feeding. An annual top-dressing of well-rotted compost can help provide nutrients and retain soil moisture.

Being Grown in Containers

Phormium tenax can easily be grown in containers. Choose a rich, organic mix over a traditional potting soil and keep the plant well-watered in summer’s heat, but don't allow it to sit in wet soil for a prolonged period of time. Don’t allow the plants to experience frost. When wintered indoors, it prefers cool temperatures but lots of sunlight.

Propagating New Zealand Flax

Lift and divide plants in the spring. You can start new plants indoors by potting larger rhizome pieces and allowing them to grow a bit before relocating outdoors. New Zealand flax can also be started from seed, although it needs a warm temperature of over 60 degrees Fahrenheit to germinate.

Common Pests/ Diseases

Mealybugs can infest plants and are hard to eradicate from inside the long leaves. Many times it’s easiest to just dispose of the infested plant. Fungal leaf spots may also mar the leaves.

When grown indoors, these plants are susceptible to many of the common pests affecting other houseplants, including mites and whiteflies. Horticultural soaps and oils are the first options for treating these pests.

Varieties of New Zealand Flax

New varieties of Phormium are introduced just about every year and they get more and more ornamental. Take a look around your local nursery to see what they've come up with this year. Be aware that the cultivars and hybrids are sometimes more temperamental than the pure P. tenax species plant. Established favorites include:

  • Phormium tenax 'Bronze Baby' has bronze foliage and grows to about 2 feet tall with a 2- to 3-foot spread. It is a good choice for containers.
  • Phormium 'Duet' is a dwarf plant (about 1 foot tall). It has green leaves edged in cream, with very stiff leaf blades.
  • Phormium 'Jester' has bronze leaves with green striping. It is about 3 feet tall.
  • Phormium 'Sundowner' has green leaves with rosy-pink margins. It is about 6 feet tall and wide.

New Zealand Flax vs. Lesser New Zealand Flax

A closely related species that also goes by the common name New Zealand flax or lesser New Zealand flax is P. colensoi. This plant is less common than P. tenax, with shorter leaves that have a lesser degree of recurve. The seed pods are twisted and pendulous in shape.

These species readily interbreed, and some of the named cultivars are crosses between the two species.

Landscape Uses

Use New Zealand flax in place of Dracaena or spiky vinca in containers and in place of ornamental grasses in garden beds. Contrast Phormium's dramatic leaves with low-growing, delicate foliage, such as perennial geraniums and coreopsis. New Zealand flax can even be grown successfully in boggy areas. The leaves can also be cut in the fall for use in flower arrangements.