Grow extra-early crops of cool-weather-loving spring vegetables in a cold frame, which are bottomless boxes with glass tops that are set directly on the garden soil. The clear glass top allows sunlight into the box, creating a mini-greenhouse. Using a cold frame, you can harvest spring greens several weeks ahead of their normal harvest time in your area. Cold frames are temporary growing areas so plant crops that mature quickly; save long-season crops like tomatoes and cabbages for the vegetable garden.
Plant salad greens, cooking greens and spinach in your cold frame for extra early harvests of these cool-weather-loving vegetables. Sow these seeds up to a month earlier in cold frames than you would in open ground in the garden.
Fast growing cool season root crops such as radishes and beets are ideal candidates to plant in the cold frame. Radishes mature in about 30 days. The beets will take a little longer---about 45 for small to medium size roots---but you can pick some of their greens for cooking or to toss in a spring salad.
Annual Flowers for Transplanting
Start seeds of annual flowers directly in the ground in your cold frame. Or sow them in individual pots and put the pots in the cold frame. Your flowers will be ready to transplant into the garden after all danger of frost has past. This works well with virtually any flowering annual, such as marigolds, cosmos, caldenula, zinnias, sweet alyssum, snapdragons and petunias.