Blue Holly and Cedar Shrubs – Can they overwinter in pots?

(Question)

I have several evergreen shrubs and 2 Female Blue Holly bushes about 2-3 feet tall. I have not decided exactly where I want them planted so they are still in their nursery pots. How should I keep them to make sure they will still be alive next spring when I hope to plant them in our garden somewhere?
I have a garage by the house and a sheltered porch protected from the wind but in a sunny location. Should they be stored in either of these places during the winter or left out sitting in their pots in the garden. I am in the Peterborough area so it can get below freezing in the winter, often.

(Answer)
The best thing is to temporarily dig these pots into the ground and remove them after the final frost occurs. The chance of losing these shrubs is high otherwise, and in addition – putting them in a sunny location in pots might also incur leaf scorch – further stressing the shrubs if they go through freeze/thaw and their roots are damaged.   If this is not an option you could simply slip the existing container into a larger container, as long as the container is not clay as they tend to crack with the cold, and fill the side with soil or mulch. The more soil in the pot, the better insulated the roots will be.
Or put them in wooden planters that are rot and moisture-resistant.  Half whisky barrels are also ideal. They are large, relatively inexpensive and can also be stained or painted. (if possible on wheels for moving them around) Cluster the containers together and move them to a sheltered spot, such as near the house or a south facing wall. Encircle the containers with chicken wire and fill with leaves or mulch. Keep plants well watered until freeze-up and check frequently throughout the winter to make sure soil is moist. Thorough watering prior to freezing temperatures and again in March and April, when the root balls are most prone to thawing—and drying out—is crucial.Once the ground freezes, add mulch to the tops of the plants.

For the cedar shrubs, you can protect them from frigid winds by driving 3-4 stakes around their perimeter, about 8-12 inches from the branches, and then wrapping them with burlap. Don’t let the burlap touch the leaves or needles or they could suffer more frost damage than if left unprotected. You could use a cage of chicken wire instead of the stakes.

Here is a useful site on container gardening;   http://www.canadiangardening.com/gardens/container-gardening/tips-for-overwintering-container-plants/a/1916/2