Answer: You'll need to start your tomato seedlings indoors under lights. Tomatoes need warmth to germinate and grow, and, unless you have a pretty sophisticated set-up, cold frames tend to have wide temperature fluctuations that can stunt the plants. I'd at least try to get them going indoors, then harden them off in the cold frame, setting them in the frame about 2 weeks before your last frost date. Plant them in the garden about a week after your last frost date. I'd do the same with heat-loving flowers.
Cool-weather vegetables and flowers can be started right in the cold frame. You'll need to wait until temperatures begin to warm in the spring -- that is, unless you want to rig up your cold frame with some type of heater to keep temperatures above freezing.
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