Originally Posted by My peeps
What is a cold frame? I'm new at all of this
Essentially a glass topped box on the ground creating a mini greenhouse environment directly on the ground to extend the growing season at the beginning and end of the growing season. It's also useful for hardening off delicate plants like tomatoes and peppers before actually planting them in the garden. I generally use it to get early and late salad greens and radishes. It is possible some years to plant lettuce in February and harvest well in to November.
I generally make mine 8-12 inches high.
Some call it a hot bed, but a true hot bed has a source of warmth like raw manure buried under it to generate heat to really extend the growing season. A true hot bed is too much work for me.
I imagine it could be done with PVC hoops and heavy clear plastic, but I haven't tried that.