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This past fall we received a question about over-wintering a Satsuki Azalea. Writing in about a tree they received in the spring, after keeping the tree outside all summer, the writer noticed that the tree was starting to have yellowing leaves, and some were becoming dry. They weren’t sure how to take care of the tree over the winter in Chicagoland.
Answer:
Azaleas require a wintering period, but are not as cold hardy as we would like around here. It is important to try not to let the root ball freeze, while still giving the plant the cooler temps it needs to lignify and set buds. Azaleas like winter temps between 33 and 40 degrees. The best solution I have been given would be an attached, but unheated garage with a small grow light for the plant. (Apparently they will weaken if kept in full darkness) I would put the pot in a box and surround it with styrofoam peanuts or something else to buffer any sudden temperature swings and check it occasionally to see that the soil stays moist.