I have the same question. Mine are actually looking great right now while in January as it's 75 degrees here. I wonder if pruning is even still necessary?

The reason for trimming them down to the ground is to remove last years dead growth for visual reasons, its not necessary, it just makes them look more attractive if they've gone dormant. If you don't have dead leaves, there is no need to cut them down. I'm only just now starting to grow purchased carex plants this year but I read it is combed out rather than cut back to remove any thatch. I have had a local type for several years that stays evergreen and I've never trimmed it. Same with blue fescue, mine is green over winter and I plan to use a hair pick or rake them out with a gloved hand in spring.

I don't cut back the muhly grasses after a mild winter, I have several varieties and I only trim if they have gone mostly brown and dormant. My grass book says they can be left alone and cut back if necessary for visual reasons every three years to renew the clump, its up to the person. I wouldn't cut back any green grasses, if they are actively growing you'll end up with new leaves having flat tops.

Brett, about dividing your fountain grass, a 4" pot usually grows into a gallon sized plant fairly quickly so if you did find some small ones for sale they would grow into nice clumps fairly fast. I have found purchasing smaller sized 4" plugs grow into nice specimens more successfully than when buying large sizes which are often root bound and difficult to get going in the surrounding soil, the small ones grow right away and fill in faster. That fountain grass you posted looks like a fairly small clump but you could divide it up to get more plants.

It is very simple. Evergreen grasses - those that hold their leaves (blades) and color all year long - are not cut back. All deciduous grasses - any that lose color and look like straw in winter and become dry and shriveled - should be cut back close to the ground in late winter/early spring. Cool season grasses can be divided in fall or mild winters; warm season grasses should wait for division until active growth commences in late spring.