Hi all! I have had great success keeping my greenhouse plants alive here in Michigan cold springs using a method an elderly Mennonite lady told me. I take a large metal pot, mine is an old canner, put two or three three wick candles in it and pour water in it to go half way up the candles. When I wake up in the morning and check my greenhouse the candles are still burning and the house is warm and steamy. I have done this for the last seven years with success.
