Mountain Flax

Basic Information

Common Name: Mountain Flax
Scientific Name: Phormium cookianum
Native Habitat: New Zealand

History / Discovery / Cultivator

Phormium cookianum, commonly known as Mountain Flax or Wharariki in Māori, is one of the two native flax species found exclusively in New Zealand. Unlike its close relative, the much taller and more robust Harakeke (Phormium tenax), Phormium cookianum is typically smaller, with drooping leaves, and tends to inhabit higher altitudes, rocky cliffs, and exposed coastal areas, hence its common names.

The genus Phormium itself was first formally described by the German botanist Johann Reinhold Forster and his son Georg Forster, who were naturalists aboard Captain James Cook’s second voyage to the Pacific (1772–1775). They encountered both species in New Zealand and recognized their immense importance to the Māori people. The name Phormium is derived from the Greek word phormos, meaning “basket” or “mat,” reflecting the primary use of the plant’s leaves for weaving by the Māori. The specific epithet cookianum honors Captain James Cook. Georg Forster’s descriptions and illustrations were crucial in bringing this remarkable plant to the attention of the European scientific community.

For centuries before European arrival, the Māori had cultivated and meticulously utilized Phormium species, particularly P. tenax but also P. cookianum, for a vast array of purposes. The tough, fibrous leaves were processed to create highly durable fibers (muka) used for weaving cloaks (korowai), mats (whāriki), baskets (kete), ropes, fishing nets, and even roofing material. Different varieties (cultivars) of flax were recognized and propagated by Māori for specific qualities of fiber or color, reflecting a sophisticated understanding of plant breeding and horticulture long before European scientific classification. Māori cultivation practices involved careful harvesting to ensure plant health and sustainability.

In the 19th and early 20th centuries, New Zealand flax became a significant export commodity. European settlers established mills to process the fiber on an industrial scale, primarily for rope and twine, supplementing or replacing hemp. While P. tenax was the main source for industrial fiber due to its longer leaves, P. cookianum was also used, especially in areas where it was more prevalent. This period saw large-scale harvesting and commercialization.

In modern horticulture, Phormium cookianum has gained popularity globally as an ornamental plant. Its graceful, arching leaves, often in shades of green, bronze, purple, or striking variegated forms, make it a versatile addition to gardens, borders, and containers. Numerous cultivars have been developed and popularized by plant breeders and nurseries worldwide, selected for specific leaf colors, sizes, and growth habits. These cultivars, such as ‘Purpureum’, ‘Emerald Gem’, and various variegated forms like ‘Cream Delight’ or ‘Sundowner’, are now widely available, contributing significantly to the plant’s status as a common and valued landscaping plant outside of its native habitat. The ease of cultivation and tolerance to a range of conditions, including coastal exposure and drought once established, further contribute to its popularity in contemporary gardens.

Plant Care Summary

Botanical Insights

Adaptations

Phormium cookianum exhibits several notable adaptations that allow it to thrive in its often harsh native environments, such as exposed coastal areas, cliffs, and mountainous regions. Its leaves are remarkably tough and fibrous, resisting damage from strong winds and salt spray common in coastal habitats. The plant forms dense clumps from a strong, rhizomatous root system, which helps anchor it firmly in unstable or shallow soils and also provides resilience against drought by storing water and nutrients. The tough structure of the leaves also discourages herbivory. The plant produces tall flower stalks bearing nectar-rich flowers, attracting birds like the Tūī and Korimako (Bellbird) in New Zealand, which are its primary pollinators. The subsequent seed capsules are large and durable, often remaining on the plant for a long time before dispersing seeds, aiding in propagation.

Propagation Methods

The most common and effective propagation method for Phormium cookianum, especially for maintaining specific cultivar characteristics (like variegation or color), is division. Mature clumps can be carefully dug up and separated into smaller sections, each with a portion of the rhizome and healthy leaves, ideally during the cooler months. These divisions can then be replanted directly. Phormium cookianum can also be propagated from seed. Seeds are typically collected from the dry seed capsules, sown in a well-drained seed mix, and kept in a warm, bright location. Seed propagation can result in variation among offspring, particularly with hybrid cultivars, but is a viable method for the species itself.

Toxicology

Phormium cookianum is generally considered non-toxic to humans and common household pets like cats and dogs. There are no widespread reports of toxic effects from ingestion of the leaves, roots, or other parts of the plant. The plant’s primary component is tough, fibrous material, which is unlikely to be appealing or digestible in large quantities. While ingestion of any plant material can potentially cause mild digestive upset in sensitive individuals or pets, Phormium cookianum is not listed as containing known toxins harmful to mammals.

Common Problems

Pests:

• Mealybugs: Can sometimes infest the base of leaves or flower stalks.
• Scale insects: May appear on leaves and stems, feeding on sap.
• Snails and Slugs: Can occasionally nibble on young foliage, especially in damp conditions.

Diseases:

• Root rot: Primarily occurs in poorly drained soils or areas that remain waterlogged, leading to wilting and plant decline.
• Leaf spots: Fungal leaf spots can sometimes appear, usually favored by high humidity and poor air circulation, though generally not severe.

Other:

• Leaf tip browning/browning edges: Often caused by dry conditions, excessive heat, salt spray (in coastal areas), or nutrient deficiencies.
• Lack of vibrant color: Cultivars selected for color may revert or appear dull if not grown in adequate sunlight.
• Poor growth/stuntedness: Can be due to nutrient-poor soil, insufficient water during establishment, or severe root restriction in containers.

Rarity & Value

Rarity:

The species Phormium cookianum itself is not rare in its native New Zealand and is commonly cultivated worldwide. However, specific cultivars developed from P. cookianum, particularly those with striking or unusual variegation patterns (e.g., complex streaks or highly contrasting colors) or compact growth habits, can be less common in general nurseries. The rarity of a specific form is often linked to its stability (how reliably it retains its characteristics), propagation difficulty (some variegated forms are slower or harder to divide/seed), or simply market availability based on demand and grower focus. Naturally occurring rare ecotypes adapted to very specific niches might exist but are not typically encountered in horticulture.

Value:

The market value of a Phormium cookianum specimen is influenced by several factors. The most significant factor is the specific cultivar; rare or highly desirable variegated forms typically command higher prices than the standard green species or common cultivars. Size and maturity also play a role, with larger, well-established clumps being more valuable than small seedlings or divisions. The quality and stability of variegation (for variegated forms) are crucial; plants with clear, stable patterns are worth more. Current horticultural trends and collector demand for specific colors or leaf structures can temporarily impact value. Provenance (where the plant came from, especially for unique cultivars) can sometimes add to its value among enthusiasts, although this is less significant for commonly available types.