Phormiums can vary in height Janpled, it depends which one you have there !

There are two types sold in the garden centres a 'tenax' (up to 6' i think) which has stiff upright leaves or a 'cookianum' (2-3')which has softer floppier leaves.
Your picture shows stiff upright ones so presume it to be a tenax type, do you remember the name of this Phormium, from when you bought it ?

It shouldn't get much taller than that, though it does appear to be P. tenax of some description - it will, though, want to continue to broaden at the base. Best thing is to dig it out, split it in half and replant half of it. It's classed as a perennial rather than a shrub, and as such, increases sideways in the soil. If you do as I suggest, it'll be a good workout, save on going to the gym....;-)

Bamboo isn't joking about the workout!
I love phormiums and have quite a few but only one tenax because of the size.Once it got to a similar size to yours, I couldn't face digging it up and splitting it. Firstly, I cut out all the damaged leaves, including bent,disfigured leaves, right at the bottom. I find a carving knife the easiest thing. Some years this is enough. When it isn't, I get an old saw and launch into it at the bottom, just above ground level. The leaves grow in fans and I just remove as many fans as is necessary to reduce it to the width I am happy with. You can't reduce the height without spoiling the look of the leaves but I think yours looks quite mature, so shouldn't get higher.

I take the cut off leaves to the council green skip because they seem to take forever to decompose on my compost tip.

I am not saying that this is the correct way of dealing with them, just what I do. I have been doing it for about eight years now and unlike many perrenials, the middle still looks strong and healthy. The whole plant looks really good and is the size I want.

Best of luck ! if you can shift one that size by hand. A few years ago I removed from my garden the cultivar 'Bronze Baby' ...had only been in the ground 2 years or so, the root mass was absolutely solid, you would need a chain saw to divide it, and probably a mechanical mini digger to take it out :0)

Oh, thanks for that Bs !!!
I have 3 Bronze Babys, one in the back and two in the front, they must love this soil because they're romping away and when i read this question i started wondering when it will be that time for me and these !!!

Hi Louise, I found it very difficult to shift once established, and one of the hardest plants I have ever had to remove.

Let's hope i can give the room they need :-/

Thank you all for your words of advice. Louise aparently it is a Tenax so maybe it has reached its full height, I hope so. Bamboo, I am already hacking away at the base to keep my path walkable, maybe I shall go it it with a little more gusto as it sounds like it is indestructable. Jan

Jan, I think it's beautiful just the way it is! You certainly seem to have the room for it. If it was mine I'd leave it alone. Do you know if all types of phormium grow flowers? I've had mine for about 6 years and it has never grown any flowers!

they all flower eventually, Skillen - you just don't know when, might be years

Yes Skillen it is a beauty and it will have to stay. The fronds are quite sharp at eye level so they are the ones that will get the chop. This is the first year that it has flowered and speaking to other gardeners in my area, Herts/Essex/Cambs border all our phoriums have flowered this year, they dont always.

Some flowered every year with me but one I have just removed after 13 years only flowered once - in the very hot summer of 2006. The flower spike was fifteen feet tall!