Can azaleas be left in the garden over the winter? Should they be covered? Our winter temperatures here in Southwestern Ontario are usually about -5 degrees Celsius, but can be as cold as -15 degrees Celsius.
Most Azaleas are cold hardy down to zone 5 and 6.
There are a few varieties that are rated for zone 4.
If temperatures drop below 25 degrees F that plants will need protection.
You may not be able to winter over Azaleas in your area.
Here is a link with more information.