Phormiums are beautiful plants cultivated mainly for their large, sword-shaped, spiky foliage. They have the potential to grow into very huge plants, so you will find that these plants need to be cut back, pruned, and/or divided to maintain healthy growth and continuously add a beautiful ornamental touch to your garden.

How can you prune an overgrown phormium? 

Phormium tenax variegata - New Zealand Flax - EXTRA LARGE SPECIMEN - 150-200cm tall

Phormium tenax variegata – New Zealand Flax

One of the drawbacks (haha yeah right) of phormium plants is the large sizes they can attain so to maintain overgrown plants, cut the tough older leaves with a sharp knife near the base to encourage new growth. 

How do I keep my phormium small?

The first way to keep your phormium plant small is to grow a variety that doesn’t grow too large or to continuously prune a large variety. The cultivation method also matters when trying to keep your phormium small.

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Regardless of the variety, a flax plant cultivated in a container will be smaller than one cultivated directly in the ground. Many container plants grow 1 to 4 feet tall, but Phormium Tenax can grow to be 10 feet tall in ideal conditions. In all, keeping this plant small is not a problem. 

Phormium with frost damage, or dead leaves – what can I do?

The best way to solve dead leaves damaged by frost and cold winters is to just leave them until the spring, and then use a sharp knife to cut them off. New leaves will grow again soon enough. 

Can you cut Phormium to the ground?

If almost all leaves have been frost damaged, and the whole plant is looking pretty sad, then cutting a phormium to the ground can be a viable option, even if just aesthetically. It will grow back eventually, but do expect 2 seasons before it’s back to full speed. 

What’s the Difference Between Phormium And Cordyline?

The main difference between them is that Cordyline forms a tall stem and can reach heights of over 16 feet, whereas Phormium forms clumps of strap-shaped leaves and can reach heights of up to 6.5 feet (depending on variety).

Another distinction between Cordyline and Phormium is that Cordyline is a genus of 15 plant species in the Asparagaceae family, whereas Phormium is a genus of two plant species in the Asphodelaceae family. 

Is It Possible To Trim A Flax Plant?

It is relatively easy to cut back on New Zealand flax. Due to the plant’s tough leaves, gardeners will need gloves and a strong pair of garden shears to trim New Zealand flax. Determine which leaves must be removed, then follow the leaf to the plant’s base and cut at that point. Cutting the leaves halfway down will give the plant a hacked, unappealing profile.

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 can I buy Phormiums? 


Last Modified: April 21, 2023