One of the great advantages of a greenhouse, of course, is the opportunity to make an early start on warm-weather transplants. Remember, however, that nighttime air temperatures can be intimidating even for cold hardy plants—a sunlover like tomato cannot take them on. Thus a further advantage of my multi-functional greenhouse is use of one of the worm bins in late winter/early spring to make a “hotbox” for tender transplants.
I place gallon jugs and 5-gallon buckets filled with water into an emptied bin, and lay scrap plywood over the tops of the buckets. A huge heat sink is created during the day, and the air temperature over the buckets at night remains many degrees above ambient. An addition of a light wood frame allows draping scrap blankets over the hotbox, cozying them even further. Over that heat sink, dug 16 inches into the earth inside a greenhouse, and with the blanket cover—Jack Frost is never going to touch my babies!