Last fall when we planted the Phormium in the ground, it was 5' and stunning, but now it is flat, gray, and bedraggled.
How far down should I prune it?
I don't know how much to leave above ground, so will let others address that.
But...speaking of phormium...has anyone ever seen it bloom in the PNW?
I had one bloom a few years back. It was 'Pink Stripe' and the bloom occurred after a hard winter when it was fairly heavily damaged. I wondered if it bloomed because it "thought it was dying". The base was about 2.5" wide and it threw up 3 bloom stalks. The hummers like it. It has not bloomed for the last 3 years and like yours the blades turned to mush this winter and I cut it back. jwww
I heard the best way to deal with this situation is to cut the plant back in spring, give it some fertilizer. Then dig a large hole next to it. Then go buy another five gallon Phormium and plant it in the hole right next to the Phormium you cut back. As for blooming, there is a large green species Phormium where I work that blooms every year. The plant is enormous, but it took a huge hit this year too. It is not dead but it looks awful and it will be a while before it re-gains it's handsome looks! I have cut most of my phormiums at home back that look like they have a chance. I dug up a few that I know were terminal.... I may do the five gallon solution in a few spots but I can't afford to replace all of them this year....sigh.
It should not be hard to tell the good from the bad leaves right now.
Save the best leaves - if any.
Cut the rest to, say, 10 inch stubs. Watch out for young healthy ones at the base of ones being cut.
Mine looks lame, but will come back for sure.
My P. cookianum are at mature size and bloom occasionally, but not every year. They weren't damaged by the freeze. I've also seen P. tenax bloom in Seattle, but again it's not a regular occurrence.
See the response to this same posting on the Ornamental Grass forum. FWIW, even though it looks a lot like a grass-type plant, flax is not a true 'grass', but related to agaves and yuccas.
Blooming is by no means a sure thing in our area but it happens often enough to be somewhat common. It doesn't even have to be an established, mature specimen to do so - I've seen it bloom in 5G nursery containers.
If you're having it freeze down your garden may be too cold for it. I've had a purple one planted on Camano Island several years ago at most go down twice already. It seems to be affecting its vigor.
Bamboo Mary - were you listening to the garden show on NPR this morning? Your answer is word for word what they said to do - but then I think they had heard it from someone else as well. I have to cut my flax down and I just hate to do it. We had unusually cold weather this year so I am willing to try it again and this next winter I will be ready to cover it if we get a warning of below freezing temperatures. I am more interested in my heucheras. The ones it pots look pretty bad, but the ones in the ground seem to be okay
Most of those are very hardy.
devorah, I heard Shon Hogan talk about Phormiums at the NWFGS. I had heard that story before but I can't remember from who. The phormium I have that survived the best was in a container of mostly sand and gravel with a little potting soil. It got flattened but it will be ok. Next year I'm going to try some sort of tent. ALL of my Heucheras look bad! Lots of vole problems this year! Grrrrr, it's always something.
Weevils may get into heucheras during summer. Those and Poyanthus primroses are the two I have sometimes had spoiled by weevils in summer. You have a plant that keeps wilting despite watering, eventually discover the roots have been eaten away, leaving a sort of husk on top of the ground.