Gardeners and plants alike love Minnesota for the cool summers and fertile soil, and roses are no exception. Floribunda, miniature, grandiflora and tea roses grow well in the state's temperate summers, but the severe winters soon end their blooms permanently. These roses, perfectly hardy in other states, need heavy winter protection. Fortunately, Minnesota gardeners are a resourceful breed and have devised methods to care for roses year-round.
Prune roses in spring while they are still dormant, making cuts ¼ inch above a leaf bud and at a 45-degree angle. Remove any canes that are crossed, old or too large. Cover the cuts with white glue to prevent cane borers from entering and damaging the plant. Water well. Actively growing rose plants need 1 inch of water per week.
Fertilize roses in early spring, after pruning. The University of Minnesota Extension recommends aged compost or manure for a steady, slow release of nutrients. Work it into the first 2 inches of soil around the rose but at least 6 inches away from the base. Supplement this with a balanced fertilizer, such as a 10-10-10 mix. The extension office also warns against fertilizing after August 1st; oncoming frosts damage the tender new growth.
Prepare roses for Minnesota winters around October 7th. The best method, suggests the Minnesota Rose Society, is to lift and tie rose canes until they form an upright column and allow the bush to rest this way for a week.
Dig a trench, starting at the base of the shrub, as long as the rose. Loosen the soil at the base of the rose and gently tip the rose into the trench. Do not allow the rose to bend above the grafting bud; you want the rose to bend at the roots, below the bud and the shank below the bud. Continue to loosen the soil around the rose if it is difficult to bend.
Spray the rose to wet it, then bury the entire plant under two to three inches of dirt. After the soil freezes, cover it with mulch to insulate the rose from temperature changes, essentially refrigerating the rose.
Remove thawed dirt gradually from tipped roses in spring as temperatures warm, usually around April 1st. Do not pull roses up through the dirt, as this may break the canes. Instead, wash or carefully shovel the loose dirt away from the canes until frozen dirt is uncovered.
When the insulating dirt is entirely thawed, gently lift the rose back into an upright position, pack the soil firmly around the base and water well. Until the canes begin growing again, water them multiple times a day to keep the bush from drying out.