I have a small potted Rose of Sharon, about 1 meter high. I live in Scarborough, Toronto. I moved it to the garage, but I think it may still be too cold for the potted plant. If I moved it to my unheated cold room of my basement, will it get enough cold dormancy period? How cold does the temperature have to be for the Rose of Sharon to bloom well the following season?
Rose of Sharon is a hardy variety of Hibiscus that can usually survive our Toronto winters if it’s grown in the ground. Have you considered planting it directly in your garden and keeping it as a landscape shrub? If this is not possible, an unheated garage should provide enough protection for winter survival. A layer of bubble wrap or burlap around the pot and at the base of the shrub will supply additional protection.
Flowering occurs on new growth from the current season, so winter conditions are less of a factor than the overall health and vigor of the shrub. Keep in mind that, if you wish to prune your Rose of Sharon, you should do so early in the spring. Pruning later in the season will impact the amount of flowering buds.
For more information about caring for Rose of Sharon, please see the following past posts from our Ask a Master Gardener site: