Dear Dolores, Ornamental grasses can be cut back to four to six inches once they are completely dormant if you want a clean looking bed or they can be left alone to enjoy the winter interest. Since yours are recent transplants and may not be that showy, there would be no harm in pruning them down. Ornamental grasses are typically a warm season plant, so do not expect to see them early spring, they will wait until the soil warms before they begin to grow.
Sincerely, Richard Hentschel
