Ever wonder what the cheapest greenhouse heater might be? For short-term frost events, it doesn't get cheaper or easier than this! Learn more about getting tropical plants through winter in Push the Zone: https://amzn.to/3UjZP5t Join our gardening community and see my exclusive food forest course, join the challenges, get gardening help and learn to grow food: https://www.skool.com/the-survival-gardener We use a cheap propane heater in our greenhouse on very cold nights; however, the real magic for keeping a greenhouse warm isn't propane or electric. It's water! Using barrels to keep a greenhouse warm works very well, and once you've bought the barrels, you have cheap greenhouse heat for a long, long time. This method of passive greenhouse heat relies on thermal mass. It takes a lot of energy to freeze water, and if you don't have a lot of days below freezing, packing your greenhouse with water storage will keep plants from freezing on frosty nights. It also helps keep your greenhouse from getting too hot in summer. We have been heating a greenhouse with water barrels for a long time. First, in our little greenhouse in North Florida, and now, we use over thirty barrels to heat a large greenhouse in Lower Alabama. Get some barrels, fill them with water, and see the difference for yourself. Barrels of water hold onto heat for a long time and let you keep plants from freezing without spending money on electric or gas. In a mild climate, this may be all the greenhouse heating you need.