Before roses are winterized, they should experience several hard freezes, at least down into the upper 20’s. This “hardens them off” to be certain they’re entirely dormant, and not going into winter too-soft. It’s important not to cover roses too early, before they’ve hardened off. Roses are notorious for they’re leaves clinging to the bush instead of dropping in autumn. Before covering roses, many gardeners hand-strip the leaves from the canes, and sometimes apply fungicide to prevent the still-clinging leaves from molding under winter protective coverings.
Not all roses need covering in the Upper Midwest’s hardiness zones 3 and 4. Whether or not to cover depends on the cultivar (named variety.) Hopefully when roses were planted, they were planted deeply, with the crown (where stems meet roots) located 4 to 6 inches below soil surface. That’s the first line of winter defense. All roses, even the hardiest, can freeze back if winter temperatures are extreme enough. Planting deeply improves the survival of the lowest stem buds. Even if the tops winterkill, the soil-protected stem buds will regenerate the rose bush.
Among the most winter-hardy roses are those developed in Canada such as Hope For Humanity, the Morden series, Campfire, Never Alone, etc. Roses that are often sold as winter-hardy shrub roses, but aren’t necessarily hardy enough for our region are the Easy Elegance series, Knockout series, Meideland series, Carefree series. These benefit from winter protection. Hybrid tea roses, with their near-perfect, florist-quality blooms, should almost always be protected for winter.
Here’s how to winterize roses:
- Nearly all roses, hardiest or tender, grow best if pruned heavily. The more tender types can be pruned in fall to make covering easier. All benefit from heavy pruning in early spring.
- Because the upcoming winter’s temperature extremes are unknown, many gardeners cover roses, regardless of variety, to insure against severe branch dieback. Covering tender varieties is almost always a must.
- Cover roses after multiple hard freezes. The idea is to keep the rose stems and roots comfortably frozen, protected from extreme cold, and protected from damaging freezing/thawing cycles. Covering is usually best done sometime during the first half of November, depending on the autumn weather.
- Material used for protecting roses can be leaves, straw, compost or shredded wood products, mounded up about 24 inches thick. To keep the covering in place, circles of chicken wire or hardware cloth mesh work well, held in place by stakes.
- Styrofoam rose cones alone don’t usually protect roses enough, as they allow too much cold air to freely circulate around the canes. Rose cones are more efficient if filled with leaves or straw. Some cones have a hinged lid to allow easier filling with material. Or you can cut a circle out of the rose cone’s top, fill with leaves or straw, and then re-attach the piece with duct tape.
- Snow is a great insulator, so shoveling extra snow in the direction of rose bushes helps also.
- Rose covering is best removed in spring as temperatures moderate, usually in early April. Keep covering material close by to use if temperatures take an extreme spring dip. Then prune all roses heavily in spring.
Best wishes for a successful rose winter. Happy Gardening!