Answer: You might experiment and try a small partially bermed cold frame, run a lightbulb or heating cable inside it for a bit of heat and cover it with insulating materials at night. Contructing it as a lean-to against a building and providing wind protection also help to keep it from getting quite as cold. You might find that the plants survive but "stall" until the weather warms up a bit again -- it will depend on the type of winter we have.
You could also grow greens indoors under lights.
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