Well... I will have some experience after this year. I wasn't sure what to do with my 'Frosted Curls' and noticed the same thing you did: The top 2/3 of the plant were pretty dry/crispy, while the lower part seemed okay.

One I cut back very hard (probably too hard, after reading your post), one I cut back about halfway, and one I left alone. So I'll let you know in a month or so how well they rebound... or not. :(

I'll jump in with questions too. My clumps are 3 years old and overwhelming the bed they share with daffodils and coriopsis. I'd read somewhere to leave carex foliage alone, but they are totally shaggy. I love the way they look with snow on in the winter, but now I would like a fresher look. Will they get new blades, or will the old keep coming? should the clumps be divided? thanx

Ok, I can only speak from experience in my zone.

I grow 4 different bronze Carex spp. All but one benefits from cutting back. I usually trim mine back to about 4 inches for the best results. I think the trick is to NOT trim them back to early in the season. As you can see in Donn's photo - there is a dried off portion & a nice fresh looking portion. Cut it back & expose the nice fresh part too early, have a late really cold period and .... opps!
Every so often I loose one but I think this is because they are not long-lived in my zone. Since I grow quite a few I can afford to experiment. Those I don't cut back usually do quite poorly and look dreadful.

Oh yeah, the one that doesn't benefit from cutting back?? Carex buchananii. A little tidying up is about all it seems to tolerate.
A.

Achnatherum, I'm glad you mentioned that about carex buchanii. I have so far resisted pruning mine and will continue to do so. That one did much better for me than the c. comans did anyway... it is said to tolerate drier soils better, and I am finding that to be pretty true.

Donn,
I have been thinking about your Carex comans. I don't think I would wait until May in your zone. A few frosty days with temps 1 or 2 degrees below zero won't hurt it - You really want to have it cut back just before / or just as its starts to make some vigorous growth.

I will probably cut mine back around the beginning of May.

A.

Well, it'll have to wait a couple of days. It's blowing and raining like stink out there right now. We've got a whopper of a nor'easter going on.

I looked at them yesterday, and there doesn't seem to be any new growth yet.

I cut back the guinea-pig potted C. comans 'Bronze' this morning. The three in-ground copies will be left alone this year.

Time will tell.

Donn,
I cut back all my 'ever-brown' carex yesterday. They were starting to put on new growth.
a.