We have a small greenhouse business in northern B. C. How do we winter potted perennials for the best survival rate? We have trees, shrubs, roses and many more.
For overwintering roses in pots, I recommend treating them like they were planted outside. Burm up a mixture of garden soils and mulch all around them, mound the dirt up onto the canes a good 8 inches too. Be sure to water them a bit prior to doing the burming and mounding. Then when all done water it all well enough to settle the soils and mulch mix in but not soggy wet. Cover the entire burmed and mounded area with about 1 1/2 inches of mulch to help hold in the moisture and hold the soils and mulch mix in place. Keep an eye on the soils moisture level throughout the winter, never watering hard but just enough to keep the soils a bit moist from time to time. The object is to keep them cold so they do not get any ideas about starting to grow too soon.