Phormium Cookianum – Learn, Buy & Grow


Phormium cookianium is synonymous with Phormium colensoi but is most commonly called mountain flax. It is the less popular specie of phormium, though with similar features and growing habits it can easily be differentiated from phormium tenax by the colours of flowers that are produced. Phormium cookianum subsp. hookeri Tricolor

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While Phormium Tenax produces different shades of orange to red flowers on tall flower spikes, phormium cookianum produces green, yellow, or orange flowers on twisted flower pods.

Phormium cookianum subsp. hookeri Tricolor

Phormium cookianum subsp. hookeri Tricolor

How to grow phormium cookianum

Phormium cookianum is easy to grow when propagated by division in spring. It can be grown in a wide variety of soil and environmental conditions including hotter, drier coastal regions.

Plant it in organically rich, consistently, moist, and well-draining soil. When planting, dig a hole that is wider than the root mass you want to plant, mix the soil at the planting site will well-rotted garden compost before placing the root ball in the hole, then backfill with the dug-up sand and step around it to firm up the soil and water generously for the first growing season.

Phormium cookianum is generally low-maintenance but will need some care and attention in its first growing year.

Where should I position phormium cookianum in my garden?

Though mountain flax can tolerate partial shade, it grows better when exposed to the full sun. Exposure to the sun will keep its foliage looking vibrant and encourage faster growth.

How tall does phormium cookianum grow?

Phormium cookianum is generally smaller than its more popular counterpart, phormium tenax. Its leaves are about 2 metres long and sometimes shorter. The flower stalks holding the twisted flower pods rise directly from the root of the plant to a height of 2 metres only.

How much does phormium cookianum spread?

Phormium cookianum grows more in diameter than in height and spreads about 2.4 to 3 metres.

What kind of soil does phormium cookianum need?

Phormium cookianum or mountain flax is not fussy when it comes to soil types but will generally grow better in an organically rich loamy soil. It can also tolerate peat moss for growth and will survive in boggy planting sites. An important feature of any soil you are using to grow your phormium is to ensure that it is well-draining.

Other types of Phormium we cover:

Phormium Black Adder, Black Velvet, Bronze Baby, Colensoi, Cookianum, Evening Glow, Golden Ray,  Jester, Maori Queen, Pink Stripe, Platts Black, Rainbow Queen / Maiden, Phormium Sundowner, Phormium Tenax, Phormium Tenax Variegatum, Yellow Wave.

Further reading:

Where to buy Phormium Cookianum?

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