Two nights ago, the temperature got down to about 27 degrees Fahrenheit.
Rachel and I buttoned up the greenhouse ahead of the cold, taping over a few little rips and loose pieces of plastic, and jamming pool noodles into the gaps between the front and back double doors.
When I opened the greenhouse to check on it yesterday, all the coffee, papayas and other tropicals were just fine, despite us having no supplementary heat other than the passive heat provided by the few dozen 55-gallon drums of water in the greenhouse.
Just that thermal mass was enough to keep the greenhouse warm enough to prevent frost. My coffee plants are the main indicators of whether or not the greenhouse gets too cold. They suffer damage in the low thirties, yet all of them were green and happy after that cold night.
Last night, it got even colder, with 24 degrees expected, so I also lit a single small propane tank heater placed in the front half of the greenhouse where the coffees are located.
When I checked on them this morning, they were all just fine, despite being on the floor where the cold might have crept around them.
I bet they would have been fine even if I hadn’t lit the heater, but I considered it to be cheap insurance. We have something like seventy coffee plants to keep warm and they are quite valuable. Some of them are not big enough to bloom and fruit, and the idea of coffee produced in Lower Alabama is quite intriguing to me. I would love to see that happen, so I’m not taking too many chances. Knowing they already went through a 27-degree night is encouraging, however.
The barrels really do make a great difference in keeping the greenhouse warm enough to avoid freezing on cold nights. They also keep the plants in the greenhouse from overheating during the day, even if I forget to open it and the sun is blazing overhead.
You can read more about this method and many other simple ways to grow tropical plants outside the tropics in my book Push the Zone.
Sometimes it’s the simple things that make a big difference. Not expensive heating systems, or climate-controlled vents or other technological solutions.
The barrels of water we place next our sensitive young trees in the yard have the same effect, keeping them from freezing on frosty nights. We put a barrel next to a tree, then cover it and the tree with a sheet, and the frost simply doesn’t touch them. Keep it simple!
