Winter Rose Protection in the North Central District
by Diane Sommers, ARS Vice President
I am enjoying a beautiful sunny morning in August as I write this article on protecting our roses for winter. Living in Wisconsin, I know that fall will be here before we know it. Just as people and critters change their habits and plan for colder temperatures, so do plants. Before we talk about “how” to protect our roses, let’s begin by understanding “why”.
Our roses, like many other plants, achieve a degree of “cold hardiness”. In Dr. Gary Ritchie’s book, “Inside Plants”, he provides some great reading on what happens to plants as daylight shortens and cooler temperatures arrive. The hardiness of roses deepens as colder temperatures gradually arrive. The key word here is gradually, because mother nature doesn’t always comply. Dr. Ritchie indicates that this cold hardiness continues to increase until late December - early January, then gradually dissipates, and is generally gone by March. The cold hardiness of plant roots is not as deep as the rose canes, but the roots are protected by the soil from extreme cold temperatures and desiccating winds. During the fall, the plant begins to produce more sugars, altering the cellular structure, and enabling the plant to survive colder temperatures. Gradually cooling temperatures lengthens the hardiness process for plants and results in more success.
Winter protection requirements are dependent on the hardiness zone in which you live. The US 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. In the ARS North Central District, we are primarily in Zones 4-5 and my comments regarding protection are for these zones. When I am asked about winter protection, my response includes the following:
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, 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.
Uncovering your roses too early in the spring can be deadly to your plant. You won’t hurt the plant by uncovering later. If you uncover the plant early and cold temperatures or wind arrives, you do need to recover. Remember the cold hardiness is generally gone by March. I typically uncover my roses about April 15 and prune end of April. This again is weather dependent. Many gardeners wait until the forsythia bloom to begin pruning their roses as Forsythia can be considered an “indicator” plant. As I have landscaped my new home I planted a few forsythia for that very reason.
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.
Rosarians in our North Central District are quite creative in how they protect their roses. 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.
Insulated Boxes: Boxes are relatively easy to make with wood frames and styrofoam and roses survive well. You also don’t have to cut the rose down as far. You do need somewhere to store the materials after winter however.
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 or higher is ideal, however, I have used R value of 5 with success. Be sure to anchor with bricks or something similar and include a deterrent for rodents who could find a home and food in the form of the rose canes. You may need to cut down your bushes, depending on the size of your concrete blanket, so wait until temperatures are cold enough before laying down.
Bury the Rosebush: While this may be a bit of work, roses generally do very well when buried. This is best used when you have a number of roses in pots. Some members have retained their “rose pit” with plywood covering it during other times of the year. It is important that there is good drainage so that the plants are not drowning in water. Also, mice poison is a must or the animals will have a feast all winter and your plants will be dead in spring. Dig your hole about 4 feet deep. Remove the plant from the pot and clean off all the soil. Tag the bush so you retain the name for next season and lay in the pit. Add your poison, and cover the hole with plywood. Place the dirt dug out of the hole on top of the plywood. Placing the dirt on top of plywood makes it far easier to recover the roses in the spring.
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 for your climate!
For more information on Gary Ritchie’s book, “Inside Plants” go to www.insideplantsbook.com
All photos by Diane Sommers