I have had this plant for a few years in zone 3. I winter protect. In late Oct/early November after I rake and bag leaves I just throw bag on top of the soil (cut miscanthus down to about four inches high first). Remove after snow melts in spring. In good summer (enough rain) it reaches about 8 feet tall. It has never bloomed (probably won't in our zone) though last year has early signs of bloom forming before cold weather came. I have never tried growing without winter protection but my method has changed from overdoing the protection (frame and fill with mulch) to just placing a bag of leaves or wood chip mulch on top - bag and all.