Q. Dear Horticulture Guy; Several years ago, we planted three New Zealand Flax plants which have done very well. In fact, they have grown so large that they are now crowding the street, the adjacent plantings around them and they’re even crowding each other. How do we control them? Should they be divided, and if they can be, how does a person do this? The flaxes are so large, tough and fibrous, with extremely sharp edges and points on the tips. It seems it would be a daunting task. Your suggestions would be most appreciated. Thank you, Chuck and Linda Price – University Place, WA
A. You are a victim of your success and plant selection. There are two species of New Zealand Flax (or sometimes called Flax Lily) found in cultivation on the west coast of the United States. The one you have selected is Phormium tenax which has leaves that can grow as long as 9 feet long. They can get as wide as 6 feet and have flower stalks 15′ tall. Yes you can divide these plants and it may be daunting to some that are used to more succulent perennials. The proper tools would be a very sturdy shovel or perhaps even better a saw to get through the fibrous root system. But this will only give you a temporary reprieve as they are fast growers and you will likely be back to their full size in a few years. One option is to relocate the divisions to areas that can accommodate their full mature size. The other option is to trade them to a friend who has space for them and get a smaller variety for your own property. Phormium cookianum (also P. cookianum) is a smaller species that has pendulous flower stalks (unlike P. Tenax which has erect flower stalks). There are small selections of this species and its hybrid with P. tenax that which only grows to about 3 feet tall and 4 feet wide. The down side is that they are slightly less hardy than P. tenax.