It may be winter, but the garden is still going. We have plenty of winter lettuce and greens growing strong this year. I can't really plant more or tend to the garden while I am recovering but I can pick what needs to be harvest with the kids help!
We've been enjoying some small patches of lettuce which you can plant in rotations like I've mentioned before . If you plant every ten or so days starting in the end of summer and into fall you can have an endless supply of greens.
Most are winter hardy but you need to check your zones to make sure they can stand the bitter cold. If they aren't frost hardy and most need at least some coverage check into a garden cover. They let the sun light in but keep the frost at bay.