I have a few 1st year roses in containers. I have 3 choices to over winter them. Outside in a protected from wind area but they would get snow, in unheated shed where they will get some light from a skylight but where I can’t access them to water them infrequently, or in an unheated garage with no sunlight but where I can give them water if they need it. Which would be best to help them survive?
Different type of roses possess various levels of winter hardiness, and sadly not all of them are winter hardy in Toronto.That being said there is no harm in trying to overwinter your rose in a container. According to the American Rose Society there are three main methods for overwintering;
The first method is planting the container directly in the soil. The soil provides sufficient insulation for the roots and protects the roots from the freeze thaw cycle.
The second method is to bring the potted plant inside an unheated garage once all the leaves have fallen and the rose has gone dormant.
The third and most difficult method is to overwinter the rose in their containers outdoors. With this method, the type of rose you have is one of the most important factor. The rule of thumb for Toronto’s hardiness zone is: zone 6a south of the 401. You need to subtract two full zones to account for the fact that the insulating properties of soil are greatly reduced when a plant is grown in a container. Therefore, to find roses that would reliably overwinter in a container, you should choose from ones that are hardy to Canadian hardiness zone 4.
In general hybrid tea and floribunda roses, and any rose that has significant hybrid tea and/or floribunda parentage, are generally hardy only to zone 5 or 6 and will not survive in a pot in our winters. When you are shopping for roses and reading the plant labels, keep in mind that the hardiness zones listed are almost always USDA zones; to arrive at a rough Canadian equivalent, add one zone. Here are a few of the more compact varieties of roses hardy to zone 4:
- Campfire
- ‘Champlain’
- ‘Cuthbert Grant’ (and almost everything from the Canadian Parkland series!)
- ‘Marie Bugnet’
- ‘Parfum de l’Hay’
- ‘The Fairy’
The choice of container and its size are also an important factor. One should never overwinter ceramic pots outdoors since they crack due to the freeze thaw cycle and the larger the container the better the insulation factor for the roots.
Growing Roses in Pots -Winterizing your roses by the American Rose Society provides detailed instructions on how to properly carry out each of the above methods.
Keep in mind the whatever method you choose it is not perfect, but in the majority of cases if you follow the instructions your rose should come through the winter unscathed.
Good Luck with your roses.
October 27, 2021