I am a novice gardener in Toronto. I want to try growing roses in containers. Will the roses survive the Toronto winter if I just leave them in the container outside? I don’t have a garage to store them and don’t have space to plant them in the ground. Thanks.
Roses can indeed be grown in containers but you will face some challenges in overwintering them here in Toronto. That being said, your best bet would be to start off with miniature varieties and then experiment with some of the larger varieties depending on the amount of space you have for containers. Here in the city, depending on how close you are to lake Ontario, you could be in either Canadian hardiness zone 5 or zone 6. Choose varieties that are bred to survive in these Canadian zones or in zones with an even lower hardiness number (4 or 3).
Choose a light coloured exterior decorative container but plant the rose in a plastic liner which will fit inside. This will help keep your rose cool in summer, warm in winter and also make moving the pot easier. Also, raise the exterior decorative pot off the ground in order to let excess moisture drain away to prevent fungal diseases and root rot. Pot size is very important too, with miniature roses needing a 12 inch pot, floribundas & hybrid teas needing an 15 inch pot, and larger hybrids & tea roses needing an 18 inch pot. Choosing the right size will give the rose adequate space for root growth, maintain good air circulation and provide enough soil to sustain vigorous growth. Make sure both you decorative exterior container and also the plastic liner have drainage holes in their bottoms.
Soil for your rose must not only provide nutrients but must also have good drainage. A potting soil designed specifically for roses can be purchased at most nurseries but a soil mix can also be made yourself by combining 40% potting soil or topsoil, 30% well aged screened compost and 30% perlite. Adding 1 cup of bonemeal to the mix will add futher nutrients as roses are heavy feeders.
In order for Roses to bloom prolifically, they need 6 hours of direct sunlight per day, so you need to find a good site for your containers. They also need to be watered daily, ideally in the morning so that they have time to dry off well before nightfall. In very hot weather, consider watering them twice a day, morning & early evening as containers dry out very quickly. Watering should continue until freeze up in late fall/early winter. Spreading a 1 inch layer of mulch over the soil surface will help stop water evaporation and will also discourage weed growth. Feed with a rose fertilizer after one month passes and then every two weeks until late August. Transplant your rose into the next size bigger pot after two years.
Ideally, roses in containers should be moved into a protected place for the winter such as a garage, shed or basement. Since you have none of these available, you should move your pots to right up against a side of the house which is protected from the winter elements. A burlap screen erected around the pots will provide extra protcction from wind but if you fill this enclosed space with leaves, it will help insulate the plants too.