Rosa hybrida L. ‘Peace’ and ‘Garden Party’ plants covered with mulch in October and November for 2 weeks were less cold-hardy, based on laboratory freezing studies, than unmulched plants. Subsequently, field injury of mulched stems was observed in December and January. Plants covered in mid-December were less cold-hardy than unprotected plants but exhibited less field injury in January than October- and November-mulched plants. Plants covered with Styrofoam cones were not injured as early as perlite-covered plants. There was no significant difference in winter injury when stems were covered with perlite, soil, or leaves. Unprotected plants had less winter stem injury than covered plants during the winter of 1978–79, when the plants were covered with snow. The following winter there was little snow cover, and November- and December-covered plants had significantly less winter stem injury in January than plants with no cover.