Click on Diagram to EnlargeThis little Greenhouse is meant to be carried outside in the sunlight of nice weather and later in the evening to be brought inside for the night. If it is kept in a cool garage, basement, be sure the temperature never gets close to freezing. I have seen tomato seedlings withstand temperatures as low as 33 degrees Fahrenheit but they definitely weren't happy! This is where the hot water bottles come in. Also you should keep the box snuggled under a cover of closely wrapped blankets on very cold nights. There will be days when the sunlight is poor. Keep them under wraps inside. A few days without sun once in a while will not effect them to much. On very cold days, but bright sunlight, you will need the hot water bottles to supplement the solar heat from the sun. Also, on good days with bright sun, no wind and near freezing air temperatures outside
I have seen little plants actually burn up in the solar heat. This is where the venting comes in and everything should be carefully monitored throughout the length of the sunlight. As soon as the box falls into the shadows and out of the warming sun, bring it inside for the night. The box temperatures will fall very quickly although the water bottles will have collected some of the heat and will slow the process a bit. You will learn a lot about going solar and greenhouse growing
with this Cardboard Greenhouse. You will also have a lot of fun showing it working to your amazed fellow gardeners. A little labor intensive. True. But it comes at a very low price.
You may contact me at: mailto:RobertLee97@Cox.net