How do I know which grasses to cut back now or to wait till spring?
None need to be cut back now and some will definitely resent it. Most deciduous grasses (Miscanthus, panicums, pennisteums, etc.,) develop attractive seedheads that add winter interest to cold climate gardens and attract wildlife, so many (maybe even most) gardeners leave them in place until doing their spring clean up. Contrary to common belief, leaving last season's foliage in place does not add any significant winter protection, so if the grasses are exposed to wind and become too messy you can cut them back at will any time during the winter.
Evergreen grasses like fescues, carex, blue oat grass, etc. should not be cut back - if at all - until new grow begins in spring.
I agree w/ gardengal as I never cut my grasses until spring and generally not until I see some new growth on some if not all.
One thing that I have experienced is that any cut grasses do not make for a good mulch, the shards, cuttings, stems, stalks or whatever the term you use these cut parts take forever to decompse if at all.
Not that anyone would really care but I've eliminated or cut down on my number of grass beds to only take 2 pickup loads of orn grass cuttings to the landfill this past year.
My pink pampass grass bloomed all summer , it is first yr. but 3 years old, it is cut to the ground ever
Feb. It is about 5 ft. tall , not counting the plumbs.
Happy gardening , caroline
When would we ideally cut back our m.sinensis ('Zebrinus') ornamental grass? And if so, how short do we cut it? And we divide it for next spring? If so, how and when?
Jill, the answer to your question is the same as that provided the OP - you don't have to cut it back now, however you can at any time between now and early to midspring if it becomes messy or begins to collapse. Generally, the recommendation is to cut it back to 4-6 inches from the ground when you begin to see new growth emerging. Because Miscanthus is a warm season grass, that could be as late as midspring, when soil and air temperatures warm sufficiently for the plant to resume growth. You would want to divide it at the same time, if dividing is necessary or desired.
I have read not to cut back blue oat grass for the winter, but what is the best way to protect it. I live in zone 5 and it previously hadn't been a problem without protection. But, the 2013 winter killed and damaged so many plants such as peach trees, grapes, knock out roses etc. and some plants had been well covered. Local nurseries have told me they don't carry blue oat grass because it is not really winter hardy in zone 5. I am afraid to damage the plant with mulch or wire filled with leaves by breaking the blades. Should I wrap in burlap?
Not sure what your local nurseries are thinking, as Helictotrichon sempervirens is perfectly hardy down to zone 4! In areas where it is evergreen, no need to cut back. In areas where it is not - most likely yours - trim back in late winter as you would with any other OG.
If root hardiness was a concern, I might consider cutting back earlier, like in late fall, and then mulching well. I wouldn't judge any plant hardiness based on last winter - it was just too out of character for many parts of the country.