Winter protection is essential for Minnesota. It must serve two functions—to keep the tempera- ture high enough to prevent winter kill and low enough to keep the roses dormant. Covering also serves to keep the sun and wind off the bushes. The sun and wind during the colder months can dry and wither canes, a common cause of winter damage.
Winter protection starts with the work you do during the summer to bring your roses into the fall season in the best of health. Here are the steps to follow to protect your roses during the winter and early spring. A good starting date would be around October 7th, and certainly before the temperatures threaten to reach 20° F. A drop below that temperature could kill or severely damage unprotected tender roses.
1. Water generously to keep the soil in good, moist condition.
2. Give your plants a good dormant spray. One of the most popular sprays for this purpose is liquid lime sulfur.
3. Starting around October 7th tie the canes of the bushes together with synthetic twine to make them easier to handle. The synthetic twine will not rot away when buried in the soil. Prune any unwanted growth at this time and remember to seal all the pruned canes.
4. Around October 15th dig a trench, starting away from and working toward the base of the bush. The trench should be as long as the bush is high. Dig it wide enough to accommodate the bush or bushes. (You can put more than one bush in a good sized trench). Use a spading fork to dig the trench and loosen the soil around the roots. Take significant care so as not to damage the roots. Pull the soil away from the shank (the root stock is just below the bud union or graft).
5. When the trench is ready and the roots of the bush are loosened, insert the spading fork behind the bush and push it into the trench. Use the spading fork, or wire loops or weights, to hold the bush down while you cover it with 2 or 3 inches of soil. If the soil you removed in digging the trench is not enough, add soil from your annual garden or other site. REMEMBER: In the tipping method, only the roots bend. Pull away soil from the shank and it will be easy for the roots to bend.
6. After the ground has frozen, cover the soil with about 1-2 feet of loose leaves or a covering such as marsh hay. Bagged leaves may also be used. Place several tins of rodent bait among the leaves to discourage the visit of small, but destructive, field animals.
7. Water the leaves well. The water cuts down on the danger of fire and also helps form ice which helps the plants stay dormant. Use fencing, such as chicken wire, around the rose bed or lay it on top of the leaves, to keep the leaves from blowing ADD away in a strong wind.
In the Spring:
Start removing the covering around April 1st. Continue removing the cover as it thaws. On or about April 15th check to see if the soil is completely thawed. If thawed, raise the plants to an upright position. Water the plants and keep the canes moist by watering them several times a day. Keeping the canes moist will prevent them from drying out until the bush begins to grow.
Feed the plants with a good balanced rose food once buds start to form. Prune the bushes once buds are formed and actively growing. Spray regularly once leaves start to form.
Other Proven Methods of Winter Protection
Note: For each of the methods listed below, follow steps 1,2,3 and 7 described above. Do not prune in fall except as described above.
Variation of the Minnesota Tip
Bend, Hill and Cover
1. Bend the bushes over very gently and carefully in an arch; pin or tie down with wire loops or stakes. Great care must be taken to avoid breaking canes off at the roots. Don’t try to bend short bushes. Mound up base of the bush with soil, (about 9-12 inches).
2. Cover the bushes with about 2 feet of leaves or marsh hay, held place by fencing around the entire bed. Be sure the cover extends out at least 1.5 feet from the center or the bush. Water leaves well.
3. In spring reverse the procedure as described earlier.
Hill and Cover
1. Mound up the base of the bush with 9-12 inches of soil. A wire cylinder may be used to hold the soil in place. Tie very tall canes to a strong stake/pole driven into the ground next to the bush. Do not prune unless necessary. Seal any pruned canes.
2. Cover the entire bed with about 2 feet of leaves or marsh hay held in place by fencing. As above water well.
3. In the spring, gradually remove the cover, starting about April 1. Beginning around April 15th, gently wash the soil off the bushes in stages. If additional soil was brought in to mound in the fall, be sure to remove the excess soil.
Polystyrene Cones are not recommended by the Minnesota Rose Society.