How to…prune a Phormium (New Zealand flax, harakeke and wharariki )

Like many people I always assumed that the only way to prune this beast (Phormium tenax) was to hack down unwanted growth.

However, on a trip to New Zealand the country of origin for this plant I discovered first hand how to prune phormiums. The phormium (new Zealand Flax) is a very sacred plant to the Maori people historically it has and continues to be used for weaving. In fact there is such a thing as the ‘Maori police” The new Zealand flax is so sacred that in one botanical garden which I visited “Maori police” would check on these plants to make sure they had not been pruned incorrectly and often they would supervise the pruning on designated days. Of course here in the UK we don’t need to worry about the plant police, but you may want to follow a similar rule. The general rule is to prune in late spring and remove any dead or damaged leaves all the way to the base. In fact, you will usually find large, linear leaves, each folded into a V-shape with 5-7 shoots on each leaf. To reduce in size remove several of the outer shoots on either side of the main ‘V’ leaf leaving the 3 central shoots. Do this on many of the outer V-shaped leaves as desired all over the Phormium. The same rule can be applied to the species cookianum. Never "top" flax as the leaves will never grow back into a point again.

Things to remember – Phormium tenax can grow very big so why not choose the smaller species ‘cookianum’. In addition to this, if you choose a cookianum, look for a clump forming one as this will be grow slower and smaller. A good example of this is my favourite Phormium, ‘jester’ - which grows no bigger than one metre in size.

Above -A picture of a New Zealand field filled with young Phormium tenax