How much to cut back maiden grass?
 

I planted a maiden grass (miscanthus sinensis gracillimus) in my front
bed last spring, and it was absolutely the star of the garden.
Beautiful growth all summer, great flowers in the fall, and it even
looked cool during our 3 months of snowy winter.

In doing some early spring cleanup a few weeks ago, I pulled out all
the loose dead plumes, probably about a third of the plant's volume.
But I'm hesitant to "cut back" the whole thing, because I'm not sure
what that really means. The middle plumes with the flower remnants are
about 5-6 feet tall, with a lot of curly wispy plumes around it. But
it's clearly all dead.

Do I really just cut it right back down to the nubs and wait for new
growth? I just don't want to do the wrong thing, since it looked so
good anchoring the flower bed.

Prune to the ground in late winter before new growth begins.
http://www.ag.auburn.edu/hf/landscape/dbpages/531.html

Newt