Hello,
I keep seeing that potted roses still need to be watered in winter if they dry out?
I am wondering a few things and am hoping I might get a answer here:
1) Is the snow not enough to act as a watering method?
2)If I winterize my roses by making a burlap cage and then filling it with straw, how do I water the rose nestled inside?do I water over the straw?won’t that make the straw wet and damp?do I open the burlap cage and then water?I am very confused on this part, hope you can help.
Laslty, 3) Do I close the burlap at the top of the roses so they are fully closed?
Sorry, I would like to know how to prep and be ready for winterizeng.
We are delighted that you have reached out to Toronto Master Gardeners with your winterizing potted roses questions.
Winterizing potted roses is a tricky business. Therefore, rose selection is of the utmost importance. Since plants in pots effectively have their entirety exposed to the elements, roots and all, they tend to freeze easier then plants that are planted in the ground. As such, in our Toronto climate, cold hardiness of the selected rose cultivars is key. Any rose that is planted in a container that you intend to overwinter outdoors, must be hardy to at least 2 zones below the zone in which you live. For example: if you are gardening in Zone 5, that means any rose you expect to survive outdoors for the winter must be cold hardy to Zone 3 and below. Roses that are more cold hardy are better able to survive, and require less protection. Roses planted to 1 zone below our zone, in our example to Zone 4, may still pull though if they are very vigorous varieties, but keep in mind that doing so is a gamble. Lastly, choose large, own-root roses if possible. (Own-root roses are grown from cuttings, and rooted.)
Budded roses (grafted roses that are more mature) should pull through the cold just fine. Likewise, mature, own-root roses have a better chance of surviving an unusually cold winter, as new growth can return from their roots in the event their canes significantly die back. This rule applies not just to roses, but to almost every other woody ornamental plant that is to be overwintered outdoors in a container.
The choice of the container is important. Roses are to never be left outside if planted in ceramic or glass pots, as these can shatter in below-zero conditions, or even suffer damage in the course of moving the plants. Also, choose the largest containers possible for your roses. Not only does this allow their roots more room to grow and expand to produce better quality plants, it also serves to better insulate your plant’s roots in the event of a deep freeze. Lastly, how deep you plant your roses in these containers is of critical importance. The bud union or crown (if planting own-root plants) should be planted at least 6 inches below the soil level, as they would be if planted in the ground in cold climate regions of the world. Never fill your pots with soil flush to the rim! Leave a margin of 6” or more from the soil line to the top of your pots, to be filled with mulch or compost for the winter. This provides greater insulation from freezing and the greatest possible protection of drying out during the winter. Most containers have decorative rings or bands around the pots. Use these as your guide for where your soil level should lie.
The greatest risk your rose has of dying over the winter is actually not freezing, because as you might have guessed, the ground in which your other roses are planted in also freezes. The greatest threat to your roses is desiccation (drying out) over the winter, from a lack of water from rain, or melting snow. Cold drying winds are naturally low in relative humidity. This is true of all woody ornamental plants that are left outdoors in containers, and why many evergreens, such as dwarf pines and rhododendrons do not survive the winter if they are planted in pots, as these plants are not completely dormant and continue to lose water from transpiration and photosynthesis. There are many different methods for preventing desiccation of your container-grown roses over the winter, all of which are described below.
- The first thing you want to do is to pull each container aside and force your roses into dormancy. This is achieved by pruning the canes of your Hybrid Tea, Grandiflora, and Floribunda roses back to about 18 to 24 inches in length, and by cutting back your climbers and large shrubs in half. Then remove all remaining leaves and spray your roses with dormant oil. By the time you are done, all your roses should look like bare-root roses that were just potted.
- The second step is to insulate the pot. First, fill the pot to the brim with mulch or compost. Second, wrap your pots with black plastic. Why black plastic? This is because black plastic (easily obtainable by cutting apart large black contractor-style waste bags) serves a dual function. It not only insulates your pots, but it also draws in heat from the light of the sun’s rays. This helps to prevent desiccation (as mentioned above), especially in the event your roses break dormancy during a winter warm spell. What usually happens during a winter warm spell is that your roses are attempting to grow, and are in dire need of water. However, the soil and water in your roses’ container is still frozen, preventing the rose from up taking the much-needed water. By having your pots wrapped in dark colored materials (and by using dark colored pots for that matter) the pot defrosts at the same time as the plant allowing your plant to remain hydrated.
- Third, once the dormant oil dries on your roses, you want to spray them with an anti-desiccant. These chemicals are made of a wax-like, waterproof resin that prevents your canes from drying out and dying back from the dry winds. This resin is similar to the wax that your bare root roses are covered in when they are shipped to your home. Do not worry about this wax preventing your roses from breaking dormancy in the Spring. It is an all-natural resin, completely biodegradable, and soluble in warm water. As a result, most commercially available anti-desiccants will need to be reapplied in the winter if you experience summer days over ~40 degrees C., with heavy rain, for it to remain effective.
- You may wish to corral your pots to keep them warm and protected from the wind. Place them up against your house, or a wood plank fence or brick wall if possible. If not, as would happen if a deck, porch, or chain link fence is in the way, then we suggest you create a loose wind break. Plastic painter’s tarps tied to the lattice work of a deck, porch, or chain link fence works great for this. Huddle your pots in a circle. The largest and heaviest pots should remain on the outside, and the smallest pots should be on the inside of the circle. If you have any miniature or young rooted cuttings in small pots, these can be inserted into the gaps between where the circles of the tops of the pots touch. Don’t worry about these small roses not getting enough light. They will be just fine, they are dormant.
Lastly, wrap the canes of the outer ring of pots with burlap, because it provides enough wind protection while letting the roses breathe, which prevents them from overheating and breaking dormancy in the winter. What you should now have looks like a holding pen of dormant roses. Do not move the roses from this pen until the last threat of freeze has passed! Prematurely moving roses out of this pen, even if they are breaking dormancy, can result in the death of the plants in the event of a late freeze. Also, do not forget to water your roses! Roses in pots cannot be allowed to have their roots dry out as the plants then run the risk of death from desiccation. If the daytime temperatures are above freezing during the winter, and there is no snow cover on your pots, and it hasn’t rained in a week or more, provide your plants with a through watering.
Below is a link to another article on overwintering roses by one of our Toronto Master Gardeners:
https://www.torontomastergardeners.ca/askagardener/wintering-roses-in-containers/
We wish you every success in your efforts to overwinter your roses, and to enjoy them again in the coming season.