- Helictotrichon - Blue oat grass - just comb through with your fingers to remove the dead leaves
- Luzula - evergreen here, but if the tips look bad you can hold them straight up and give them a hair cut
- Sesleria - evergreen for me, but does have some dead leaves in it, so I gave mine a haircut this year
- Carex* - technically not a grass, but looks like one.
- C. muskingumensis - don't be tempted to leave any green that might be showing. Cut down right back so that you have a sturdy plant when it starts to grow
- C. flagellifera - I know it looks dead, but if the leaves don't pull out easily, just leave them be, because they are alive
- C. caryophyllea - evergreen for me, or nearly so. I trim only if it looks bad.
- Juncus - evergreen for me, but depending on whether or not it looks ratty, I do or do not cut it back.
So a crewcut is not necessary. Just give them a trim, as the new growth will soon hide any of the leftover dead foliage.