By Tsb
United Kingdom 
I have several ridiculously large flax plants (phormium) at a new house which I need to reduce radically in size. Great that they are healthy but they've gone mad! How can I prune them back properly - ie also pruning the healthy leaves. Should I pick out the longest leaves, and cut them as near to the base as possible? Can I hack away a whole part of the root? Also when is the best time of year to do so?
18 Feb, 2013
Answers
My phormium grew out of control. I have been very hard on it and chopped away at the base to remove many of the outer root systems. Finally i was able to lift the whole thing out of the ground and pull off all uneccessay leaves and detritus it was then replaced and seems to have taken very well indeed. I have potted on many of the root clumps that I pulled off.
18 Feb, 2013
The best time for a general tidy up which involves removing damaged and unattractive leaves at the base is around April, or when spring is here. As for reducing the size, there's only one way I'm afraid, and that is to dig each one out, split it so you've got good root sections on each piece, and replant the part/s you want.
18 Feb, 2013