Four Methods of Overwintering Roses
The first and desired is to be able to do nothing and have the rose survive on its own.
Cold weather gardeners can do this by growing hardy roses such as Explorer, Parkland and Buck roses. Many of the species roses and shrub roses will also survive quite nicely on their own.
But you're likely looking for information on overwintering tender roses. The trick here is to stop the bud graft from freezing or being damaged. You can do this in one of two ways.
The first is to plant the bud union deeply. This will protect the bud union and all you do is cut the canes to the ground in the fall. You do this to remove any overwintering source of black spot and because the canes will die to the ground over the winter anyway.
The second is to use a “system” to protect the bud union in your overwintering roses efforts. Traditionally, rose gardeners have “hilled” their roses by cutting the canes back to 12-18 inches and then made a pyramid over top of these canes with soil. If you choose to do this, then do bring in the soil from another part of the garden. Digging around the rose roots to hill up the canes while exposing the tender roots to cold defeats the entire exercise.
If you use a hilling system, it is an excellent idea to spray the canes with a lime-sulphur and dormant oil combination before you hill them up. This will help knock back fungal problems.
Some gardeners swear by peat moss and hilling up the cut canes with this material keeps them dry and warm. Others use Styrofoam containers of some description and cover the canes with these.
Overwintering Roses by Covering
Research at the Royal Botanic Gardens in Hamilton Ontario suggests that gardeners can use a foam blanket (called polyfoam) to cover their roses and expect increased survival rates in overwintering roses. Mind you, the garden looks like a sheet of foam was laid over it – kinda like a huge white sandwich landed from outer space. But the roses will survive if the edges are sealed with soil to prevent the wind from lifting the foam.
Some gardeners wrap their roses with burlap and fill the enclosed space with leaves.
Some make little enclosures of wire or snow fencing and fill the enclosed space with leaves or an insulating material in an attempt to overwinter roses.
Whatever material is used, the objective is the same – to protect that tender bud union from dying.
My experience with both systems is that the deep planting system is far and away the easiest way to overwinter roses and I *never* lost a hybrid tea rose to winter damage in almost 20 years of gardening at the farm. Mind you, as I said on the planting page, if you don't feed them rigorously, you had better use the traditional system.
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