Local advice is preferred for this question, but here are some general guidelines for winter care of rose bushes for those living in colder climates. The major dangers to the plant in winter are the drying of the wind, the effect of alternate thawing and freezing cycles on the plant when winter temperatures fluctuate, the inability of the plant to take in water if the soil is frozen, and damage from the cold itself to the canes and bud union.
- If you live in an area with harsh winters, plant cold‑hardy roses. Your choices are more restricted that way, but you will save yourself a lot of work and heartbreak. Many once blooming old roses are very cold‑hardy; of the repeat bloomers, rugosas are rock‑hardy, and many Austins and other shrub roses will do okay. Many yellow and lavender roses are especially tender.
Unfortunately cold‑hardiness is not an exact science; conditions such as wind affect roses severely in cold weather (by drying them out), and so zone ratings are only a first approximation. Beware of books that rate roses ‘cold hardy’ or ‘not cold hardy’ — they are likely referring to conditions in the UK, which has mild winters. Beware also of catalogs that overrate cold‑hardiness because they want to move more product.
- When in doubt, plant own‑root roses. If they die back to the ground in a particularly severe winter, they will grow back from the roots fairly quickly. This advice is not applicable to once‑bloomers, because these usually flower only on the last year’s canes. own‑root Old Roses and English roses are available. Hybrid Teas are almost always sold as grafted plants, and it is difficult to find own‑root plants.
- In the fall, reduce the amount of Nitrogen fertilizer used. This, combined with lower temperatures, will slow the production of new tender growth, and will allow the existing growth to harden off.
- Stop deadheading about September 1 for zones 4 and 5. This will allow the plant to form hips. The formation of hips encourages the plant to slow down growth, slow blooming, and harden the canes, all preparing the plant for dormancy.
- Understanding rose dormancy will help to determine the proper time to prune during the period from late Fall to early Spring. During dormancy, the sap has left the canes and they are simply empty tubes of cellulose. Pruning too early (before the sap runs back) cuts some of the nutrients out, so you must be sure the plant is dormant before fall (winter) pruning. Winter dieback generally occurs from the end of the branches (canes). Pruning removes the available length that can die back before reaching the ground. Also, pruning a semi‑dormant plant stimulates growth and sap flow in the pruned region. For a plant going dormant, this is bad because it inhibits dormancy. For a plant waking up (springtime) it’s good because it stimulates growth. Ideally pruning should occur before sap is fully flowing.
- To prevent disease/fungus from over‑wintering, clean the rose bed by removing leaves and other debris. Spray the bush with dormant oil to kill bacteria on the bush and on the ground.
- Protect the crown of the rose. This is critical since the crown is where you want the new canes to come from. There are several methods of protection to choose from.
- Cover the bed at least a foot deep with tree leaves. Do not use rose leaves as they may harbor disease. Oak leaves are best as they seem to drain better.
- Cover the bed with straw.
- Use rose cones.
- Make a mound with soil or mulch to cover the crown.
- Wrap the whole plant in burlap if necessary, in addition to one of above methods of protecting the crown.
Timing is important. Covering the rose too early is unwise as it may prevent the rose from hardening properly and will slow the onset of dormancy. Covering the rose too late may risk damage from the cold.
- Climbers or long canes may benefit from being tied to avoid thrashing from the wind. Canes may be protected from drying winter winds by wrapping them in burlap with a layer of straw for insulation. In severe climates long canes may need to be tied and buried.
- Keep the soil well‑drained, especially as the spring rains come.