Hi Lisa, I am also in zone 7 (Memphis). I plant lettuce, spinach, carrots, radishes, & brussel sprouts all winter. Since you have a raised garden it makes it that much easier. Plant your seeds, mulch with a 2 in layer of pine needles (free). I place a piece of plastic sheeting over my raised bed until the seeds germinate and then keep it rolled back unless it gets very cold (way below freezing) All these plants like a bit of frost and the raised bed and pine needles hold in enough heat to keep the ground pliable. Grow your garden all winter, no need for a greenhouse.
