By Diane Sommers, ARS Vice President
As colder temperatures arrive, our garden work transitions to clean up and getting our plants ready for the colder temperatures that will soon arrive. Of course winter protection requirements are dependent on the hardiness zone in which you live. The U.S. Department of Agriculture established 13 hardiness zones, which consist of geographical areas defined to encompass a certain range of climatic conditions relevant to plant growth and survival. While my experience is based upon the zone 5 in which I live, the concepts are consistent in areas experiencing cold, winter weather. Success in overwintering your rose bushes is not for fall only, and general horticultural practices can improve your success rate overall.
• When planting your rose bush, make sure the graft is 2 - 3 inches below the soil line. If you need to cut the plant down in spring to close to the soil line, you have a better chance of your rose coming back.
• Healthy bushes have a higher probability of making it through winter (keep your roses free of diseases such as blackspot). This enables the plant to continue to create those sugars that help with cold hardiness.
• Stop fertilizing near end of August; encouraging continued growth with fertilizers reduces the ability of roses to create the sugars that are important for cell survival in the winter.
• If you need to cut down your rose bush to cover it, don’t cut too soon or you will stimulate more growth. I typically cut my roses down end of November or early December. Depending on the method of protection used, you can actually wait until spring to cut them down.
• Don’t cover your plants too soon. Let the critters find their homes first. In my area, I typically cover roses in early December, but of course this is weather dependent.
• Roses in pots will not survive in the pot outdoors during winter. You can bring them into the garage or remove the plant from the pot and bury in the ground for winter. Roses overwintered in the garage require a cup of water every three weeks.
• No matter what method of protection is used, be careful when uncovering in the spring. Early new growth needs to be protected. The concepts of winter protection is as important to plant success in the spring as in the fall!
• Each year will be different - the weather will dictate what you do and when you do it.
No matter what method is used, the goal is to protect the plant from extreme cold temperatures and desiccating winds that destroy the plant cells. The number of rose bushes you have may play into what works best for you. Here are a few of the most common methods:
• Do Nothing: Of course this is the easiest, but you may loose some roses. Plant hardy roses to ensure success and be sure the graft is under the soil. Gather the canes and tie together to prevent plant damage from winter winds.
• Gather dry leaves around the plant. It is best to use some sort of “collar” to keep the leaves in place for the winter. Something as simple as a newspaper folded and stapled can work. Oak leaves work great, as they don’t mat down and allow air to continue to circulate.
• Fir Branches: Cut the branches off of your Christmas tree after the season and place over your rose bush. You will be amazed at how well this protects the plant. I have been known to gather branches from the neighbor trees that have been left at the end of their driveways for pickup.
• Rose Cones: When using rose cones, be sure to cut some holes (2” - 3” inches) throughout the cone, to enable air to flow through the cone and prevent mold from forming. Also, placing a brick on top of the cone will help keep the cone in place all winter. I typically cut open the top to also enable air flow.
• Concrete Blankets: This is a relatively new technique used in our District with great success. Concrete blankets are actually used in construction, typically for pouring concrete, to keep the ground or newly poured concrete from freezing. They are typically 1.5 inches thick and come in various sizes. The R values relate to insulation ability and the higher the R value, the more protection will be provided and the higher the cost. One member even had them custom made for her garden, but that is not necessary. Concrete blankets are easy to find at home improvement or building stores. An R value of 7.1 - 7.5 is ideal, however, I have used R value of 5 with success. Be sure to anchor with bricks or something similar and include plenty of mice poison under the blanket. You will need to cut down your bushes, so wait until temperatures are cold enough before laying down.
Photo shows a concrete blanket used for
winter protection in a bed of miniature roses
Hopefully this helps you with some ideas on how to protect your roses through your winter and spring weather. The good news is that hybridizers continue to develop roses that are hardy with little to no protection. A few of those in my garden include: ‘Golden Unicorn’, ‘South Africa’, ‘All the Rage’, ‘Olivia Rose Austin’, ‘Violet Hour’, ‘Above and Beyond’, ‘Quietness’, ‘The Fairy’, ‘Erin Alonso’, and ‘Jasmina’. And don’t forget that Consulting Rosarians and your Local Rose Society are great resources for identifying hardy roses and winter protection options in your climate!