They've probably set their flowers this late so chop off everything to the ground. You need to rearrange plants this dormant season for lower mainainence.

Yes, you will lose flowering for this season if you cut back now. But just as with turf grasses, it will not harm the grass to be cut back, even partially. Warm season grasses like Miscanthus will produce new growth, but not produce flowerheads/plumes.

In your zone, the division and/or moving of warm season grasses should be done in late winter or early spring, when you would typically cut back last season's growth.

man am I glad that you are a regular poster, gg.
so, for the future,when or at what height do you think is the latest i could whack miscanthus and still get bloom?thanks so much
mindy

Mindy, I'm not sure I can answer that with any kind of accuracy :-) I have no experience growing warm season grasses in your climate zone so have no idea how they perform. Here, our springs are long and quite cool (this year, downright cold!) and warm season grasses barely start producing top growth much before May and seldom produce flower plumes before September. If I wanted them to develop plumes/flowerheads, I'd be very reluctant to cut them back at all during the growing season.

Like other plants, ornamental grasses don't read the books on how big they are supposed to grow and IME, especially with Miscanthus, can get quite a bit taller than many labels or sources suggest, particularly when well-established or when grown in very good soil conditions. I think relocating to a more suitable position where they can grow unchecked without shading out other, smaller plants will be a more favorable approach than attempting to cut back during the growing season. Afterall, the flowers/seedheads are one of the biggest attractions of these grasses and it would be a shame to lose them.