Temperature tolerance refers to a rose bush’s ability to tolerate extreme temperatures both in winter and summer. This article is going to concentrate on how to manage the extremes of winter and the cold. Rose bushes will be able to survive easily in certain temperature ranges.
Gardeners can extend that range by providing some winter rose care that includes mulch and insulation. There are also certain roses that have been bred to withstand extreme low temperatures.
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Determining Your Growing Zone
The first step to successfully maintain your rose bushes through the winter season is knowing the growing zone you live in. This will tell you what the estimated date of the first frost is in fall and the last frost in spring. It also tells you what the average temperature range will be.
Selecting the Optimal Rose Bush for Your Grow Zone
It is estimated that there are over 30,000 varieties of roses worldwide, all of which are descendants of about 150 original plants. Roses continue to be developed to improve their disease and pest resistance, their cold and heat tolerance and their color and bloom. Each year, additional new varieties are introduced.
Knowing your grow zone will help you to select the best roses for your area. So how do you select the best rose for your grow zone? Purchase your plants from a reputable rose grower. Each rose should have its cold tolerance included in the description of the rose. Another source of information is other local gardeners. If they have a rose that has been growing in their garden for several years, it is likely to do well in your garden as well.
Lastly, there are many organizations dedicated to roses and the gardeners who grow them. Check to see if there is a branch in your area. If you can’t consult with a local gardener, follow this guidance for selecting the right rose bush for your grow zone:
Greatest Cold Tolerance
These roses will survive in temperatures down to -30 degrees (zone 4). That doesn’t mean they don’t need help, as you will have to winterize your roses to maintain them through the winter. Generally, varieties of shrub roses and floribunda roses will fall into this category.
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Party Dress, a groundcover rose, and John Cabot, a shrub rose, are cold-tolerant to zone 4. Another choice is the Nootka Rose, a shrub rose developed for Alaska and cold-tolerant to zone 1. This rose is cold-tolerant to -40 degrees.
Mid-Range Cold Tolerance
Most roses in this temperature zone include hybrid tea roses, grandifloras and climbing roses. These roses will tolerate temperatures of zones 5-9. They will need protection from the cold if lows will be below 10-15 degrees. That includes zones 5 and 6. Great choices for mid-range roses include the Iceberg climbing rose, Simplicity roses and the Double Delight tea rose.
Hot Weather Roses
A growing number of areas of the country are suffering the effects of extreme heat and drought due to global warming. If you are in an area that has begun to have regular heat waves for extended time spans, be sure to check the information on the roses you are thinking of purchasing to see if your choice is heat-tolerant.
How to Winterize Your Roses
Winterizing starts when you plant your roses. Healthy plants will be able to survive the stress of cold and winter weather, where weak plants will have a more difficult time. Plant your roses in full sun with well-draining soil.
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Have the soil tested to make sure it contains all the nutrients needed. Add compost each year or more frequently if you have sandy soil. Use a two- to three-inch layer of organic mulch to provide stable soil temperatures and to retain moisture.
When fall arrives, stop deadheading your roses. This will help the rose to enter dormancy and provide you with some beautiful rose hips to add to your fresh wreaths and other décor at Christmas. Discontinue fertilizing but do continue to water as needed until the ground freezes. Remove all plant debris from the ground surrounding the rose plants to prevent disease.
Trim any broken or dead branches. If you feel your plant will be susceptible to breakage due to the weight of snow, you can trim those branches; otherwise, don’t prune at this time. Spray the rose with a dormant spray as this will kill any pests and prevent fungal diseases.
For zones 1-6, take these additional steps with your rose bushes:
- Hybrid Teas and Floribundas — Cover the crowns with six to 12 inches of clean soil. Then, cover the plants and mound with straw or use rose cones.
- Tree Roses — Gently remove the soil from one side of the rose and lower the rose to that side. Cover the tree rose with straw and then soil.
- Climbing and Groundcover Roses — Cover the base with soil as with hybrid tea roses. Gather the branches together and wrap them in burlap. Tie them and, if the weather is severe in the winter, anchor the branches to the ground and cover with straw and then soil.
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- Wait Until the Ground Freezes — Don’t add straw or rose cones until the ground has frozen. If you add too soon, you will insulate the ground and the rose from freezing and the rose will not become dormant. It also could attract four-legged friends looking for a nice warm home for winter.
For zones 7-8, take this additional step with your rose bushes:
- Cover the Crown — Apply mulch over the crown if a colder than usual winter is forecast.
By understanding your growing zone, you can select the optimal rose bush to tolerate your local winter temperatures. Then, just follow these tips and make sure your rose bushes are set up to weather winter temperatures and bring joy and beauty to your gardens for years to come.