Phormium tenax (New Zealand flax)

Physical characteristics

Phormium tenax develops in dense tufts of rigid, straplike leaves that commonly reach lengths up to about two metres. Leaves arise from a central rootstock and are arranged to form an architectural clump. Flowering follows on stout, erect scapes that may be much taller than the foliage; the nectar-rich flowers attract birds and insects. Cultivars vary in leaf colour — green, bronze, striping or variegation are common — which has increased its popularity in landscape design.

History and cultural significance

For centuries the plant has been an essential resource for the indigenous Māori of New Zealand. Fibres extracted from the leaves were processed and woven into clothing, containers, fishing lines and floor mats. The skills of harvesting, preparing, and weaving harakeke are culturally important and continue to be practised today. In the colonial era the fibres also supported a commercial industry producing ropes and other goods through the 19th and early 20th centuries.

Uses and cultivation

Practical uses of Phormium tenax fall into two broad categories: traditional fibre and modern horticulture. Fibre remains used in artisan weaving and conservation of cultural crafts, while gardeners prize the plant for its bold form, tolerant behaviour in coastal and poor soils, and low maintenance. It is propagated by seed and division; many named cultivars have been selected for leaf colour, size and flower traits, making it a versatile plant for borders, architectural planting, and container culture.

Ecology and invasive behaviour

Outside its native range, Phormium tenax can behave invasively, forming dense stands that outcompete native vegetation and alter habitats. Several regions have reported naturalised populations that spread along coasts, riverbanks and disturbed sites; authorities and ecologists often list it among species that require monitoring or control as an invasive plant in sensitive ecosystems. On some islands the species has had pronounced ecological impact.

Notable cases and distinctions

A specific conservation concern has been recorded on Saint Helena, where Phormium tenax has expanded into areas occupied by rare native plants and contributed to habitat change threatening species such as Elaphoglossum dimorphum. Botanically, Phormium tenax is typically distinguished from its close relative Phormium cookianum (a smaller, more tufted species) by its larger size and robust inflorescences. Management strategies balance its horticultural value and cultural importance with ecological safeguards where it becomes a pest.

• Key traits: evergreen clump, straplike leaves, tall flowering stalks.
• Main uses: traditional weaving fibre, ornamental planting, erosion control in some settings.
• Concerns: invasive potential outside native range; requires monitoring in sensitive habitats.