From Cold Frame to Grow Frame:
Knowledge is Power!

But the single most important item I’ve revealed here is the insulated cover which is placed over the growing unit every night the temperature approaches or goes below freezing. This is the “bottle cap” to our thermos bottle. It must be air tight and have as much insulating power as possible. I spend much of my time testing different solutions for this. If you can keep the heat you’ve collected all day INSIDE the box overnight, you can keep your garden alive for most of the year without auxiliary heat. Regardless of design, as long as your grow frame contains these elements, it will work! Larger backyard greenhouses depend upon the same principles. If yours is getting too hot by day or too cold overnight give it a new appraisal based on these proven essentials. Even though the days grow shorter in winter and plants grow slower it is possible to maintain them and harvest your rewards even at Christmas. One year I shared vine ripened tomatoes with my neighbors!

Conclusion. JT