Overview

Phormium cookianum is a perennial in the genus Phormium, part of the Asphodelaceae family. It typically grows around 1.2 m tall. Phormium cookianum grows best in full sun, and tolerates most soils. Its UK hardiness is rated H5. It is native to New Zealand.

About

Phormium cookianum is a perennial in the Asphodelaceae family native to New Zealand. It typically reaches about 1.2 m in height. The plant flowers from June to August. It prefers full sun and soils that range from sandy to clay, tolerating moist or wet conditions.

Wikipedia contributors, CC BY-SA 4.0 — Phormium colensoi

About the genus

Phormium is a genus of two plant species in the family Asphodelaceae. One species is endemic to New Zealand and the other is native to New Zealand and Norfolk Island. The two species are widely known in New Zealand as flax or their Māori names wharariki and harakeke respectively, and elsewhere as New Zealand flax or flax lily, but they are not closely related to the Northern Hemisphere's flax, which is native to the region extending from the eastern Mediterranean to India and has been used by humans since 30,000 B.C.

Wikipedia contributors, "Phormium", CC BY-SA 4.0 — Phormium

In the garden

Phormium cookianum is a perennial member of the Asphodelaceae, native to New Zealand and commonly grown for its upright clump form that reaches roughly 1.2 m. It flowers in the UK from June to August. The species carries a hardiness rating of H5 — hardy — and is also rated USDA 7–10, so it can be left outdoors through typical UK winters without routine winter protection in most areas. Site selection should favour full sun. Soil type is flexible: sandy, loamy or clay soils are all acceptable provided the ground does not become bone-dry. This plant tolerates soils described as moist but well-drained through to genuinely wet ground, so it can be used where moisture lingers after rain or where the soil remains damp for extended periods. Avoid planting in dense shade if you want reliable flowering. In a UK garden Phormium cookianum works well where a sun-facing, moisture-retentive spot is available and a distinct, upright planting is required. Its seasonal display of flowers from June to August gives a clear summer flowering window to plan around for companion planting and structural contrast within borders or alongside wetter beds.

Growing conditions

Best soil and position for Phormium

Sunlight

Full sun

Soil type

Sandy, Loamy, Clay

Soil moisture

Moist but well-drained, Wet

UK hardiness

H5

Plant details

Phormium cookianum size, habit and characteristics

Plant type

Perennial

Height

1.2 m

Native to

New Zealand

Frequently asked questions