Winterizing Modern Roses
If you grow grafted, modern bush roses such as hybrid teas, floribundas and grandifloras in USDA Hardiness Zone 6 and colder, you must provide winter protection to ensure their survival. The first step is to wait until the roses are dormant, an event usually signaled by leaf drop in November or December. At that point, the sap in the stems has returned to the roots, and you can safely prune the canes, if necessary.
On grafted roses, the most important area to protect is the graft union, that swollen, knobby area usually near the soil line. Cover the crown with a 1-foot-deep layer of bark mulch. Bark mulch protects the crown and allows air to circulate, but soil, leaves, and grass clippings tend to hold too much water, which can cause rot.
Cut back canes to 2 to 3 feet tall after they're dormant to prevent canes from wind damage. If a deep cover of snow is reliable, pruning is less necessary. Canes die not only from cold temperatures, but also from temperature fluctuation and drying winds, conditions that snow (or some other covering) can prevent. Wrap the canes with burlap to protect roses. You can also use rose cones, a sort of Styrofoam bucket placed over the plant, but they cost more and can (sometimes) blow away unless anchored properly in the garden.
Charlie Nardozzi is the senior horticulturist at National Gardening.
Photography by Suzanne DeJohn/National Gardening Association