Pocket BotanistPlant guide
New Zealand Flax.
Phormium tenax
Pronounced FOR-mee-um TEN-aks
Also known as Lowland flax, New Zealand Flax, New Zealand hemp, New Zealand-flax, New Zealand-hemp, Swamp flax, harakeke
New Zealand flax is a striking architectural plant known for its long, sword like leaves that add a bold vertical element to any garden. It thrives in a variety of conditions and is quite popular for its tough, low maintenance nature. You will love how it creates a dramatic focal point in your landscape.
At a glance
- Care level
- Easy
- Plant type
- Evergreen perennial
- Light
- Full sun to partial shade
- Indoor light
- bright-indirect
- Water
- Every 7 to 14 days
- Mature size
- 300 cm tall
- Growth rate
- medium
- Hardiness
- USDA 8 to 11
- Bloom time
- Late spring to summer
Care
Plant in well draining soil and ensure it gets plenty of light to maintain its vibrant color. Watch for signs of root rot if the soil stays soggy for too long. Trim away dead or damaged leaves at the base to keep the plant looking tidy.
- Watering
- Allow the top few centimeters of soil to dry out between waterings.
- Feeding
- Apply a balanced liquid fertilizer during the active growing season.
- Pruning
- Remove old or damaged foliage once a year to encourage fresh growth.
- Repotting
- Repot when the plant becomes root bound or outgrows its container.
- Soil
- Well draining, fertile soil
- Soil pH
- Neutral to slightly acidic
- Temperature
- -5 to 35°C
- Humidity
- 40 to 60%
- Drought tolerance
- moderate
- Lifespan
- Perennial, typically 15 to 20 years.
- Deer and rabbits
- high
Signs it needs repotting
- Roots growing out of the drainage holes.
- The plant pushes itself up and out of the pot.
- Water runs straight through without soaking in.
Safety
- People
- The plant is generally considered non toxic to humans, though the sharp leaf edges can cause physical cuts.
- Pets
- This plant is generally considered non toxic to cats and dogs.
- Children
- Keep children away from the sharp, serrated leaf margins which can easily slice through delicate skin.
- Contact allergens
- The stiff, blade like leaves can cause mechanical skin irritation or cuts if handled without gloves.
- Airborne allergens
- There is no significant evidence that this plant acts as a common respiratory allergen.
- Edibility
- While the nectar is traditionally consumed, the foliage is not considered edible and should be avoided.
How to identify it
- Long sword shaped leathery leaves
- Leaves grow in dense basal clumps
- Tall flower stalks rise above foliage
- Fibrous leaf texture
- Vibrant leaf colors including bronze or variegated
- Height
- 1 to 3m
- Spread
- 1 to 2m
- Leaves
- green, bronze, red, yellow, evergreen
- Flowers
- red, orange, yellow, 2 to 5cm
- Fruit
- black, Autumn
Common problems
- Mealybugs — These small, white, cottony insects hide in the leaf bases and suck sap from the plant.
- Phormium leaf spot — Fungal infections cause unsightly brown or black spots on the foliage, often due to poor air circulation.
Growing it
- Propagation
- division, seed
- When to plant
- spring, autumn
- Overwintering
- In colder regions, tie the leaves together to protect the crown from snow and ice buildup. If you live in a very cold area, move the container into a sheltered, frost free spot for the winter.
- In containers
- It grows very well in containers, but you should use a pot at least 15 to 20 gallons to accommodate its large root system.
Division
- Dig up the entire clump in early spring.
- Use a sharp spade or saw to cut the root mass into smaller sections.
- Ensure each section has a healthy portion of roots and leaves.
- Replant the divisions immediately into well draining soil.
Pair with plants that have similar water needs to ensure everyone stays happy in the same bed.
Grows well with
- Hebe — These shrubs provide a nice textural contrast and share similar coastal growing requirements.
- Carex — Sedges create a soft, grassy base that complements the rigid, upright form of the flax.
Keep away from
- Small delicate flowers — The aggressive root system and large size of the flax can easily crowd out smaller, slower growing perennials.
Similar species
- Mountain Flax — It is a smaller, more arching relative that fits better in tight garden spaces.
Science
- Family
- Asphodelaceae
- Genus
- Phormium
- Order
- Asparagales
- Class
- Liliopsida
- Native range
- New Zealand and Norfolk Island.
- Conservation
- It is not currently threatened, but wild harvesting should be done sustainably to protect local populations.
It grows in diverse habitats from swamps to coastal cliffs, utilizing its deep root system to stabilize soil.
- Value to wildlife
- nectar source
- Pollinators
- bees, birds
- Uses
- architectural accent, coastal landscaping, privacy screening, erosion control
Through the year
Ecological indicators
- Salinity
- 7/9
- Soil reaction
- 5/9
- Light
- 7/9
- Temperature
- 6/9
- Moisture
- 5/9
- Nutrients
- 4/9
Taxonomy resolved against GBIF.
Questions people ask
- Does it need a lot of water?
- It prefers consistent moisture but is quite adaptable once established.
- Can I grow it in a pot?
- Yes, it makes a fantastic container plant if you use a large, heavy pot to prevent tipping.
Where the name comes from
The genus name Phormium comes from the Greek word for a wicker basket, referencing the plant's use in weaving. The species name tenax means tenacious or tough, describing its strong leaf fibers.
Good to know
- It is commonly known as New Zealand flax, though it is not related to true flax.
- The leaves can grow up to 3 meters long in ideal conditions.
- It is incredibly tough and thrives in salty, windy coastal environments.
Is your new zealand flax looking unwell?
This page is a general guide. Pocket Botanist diagnoses problems from a photo of your actual plant, works out watering for your light and conditions, and reminds you when care is due.
This guide was generated with AI and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.