Hi Heather,
I too am in zone 5. My clumps of Miscanthus sinensis 'Variegatus' look like they are just beginning to get ready to bloom. Could be a week or two at this rate.

As for trimming, go for it! I often trim back any leaning grasses, especially those that grow along pathways. Unless the shoot has broken or bent right over at the base you can often cut it off at about 2 or 3 feet and then it (they) can act as a natural girdle.
A.