Fresh vegetables are often considered a reward of summer, but you can continue harvesting many plants even after the first snows have fallen. Coldframes are glass-topped boxes that work as miniature greenhouses in the garden, helping maintain warm temperatures in the beds. Using coldframes in conjunction with vegetables that thrive in cooler weather helps ensure your winter garden in successful and productive.
Spread a 2-inch layer of compost over the garden bed and work it into the top 6 inches of soil. Compost aids drainage while adding nutrients. Prepare a garden bed that isn't prone to standing water in winter and receives as much winter sunlight as possible.
Sow the seeds or plant the vegetable seedlings in the bed in late summer or early fall, as indicated on the seed packet for the specific plant. Generally, winter greens such as lettuce can be planted up until the first frost, while root vegetables must be planted in late summer.
Spread a 3-inch layer of straw mulch over the bed before the first hard frost in fall. Mulching preserves soil moisture but also helps insulate the soil against winter freezing.
Water the plants as often as necessary to maintain moisture in the soil to a 6 inch depth. Soils retain moisture better in cooler weather, so plants may not require frequent watering.
Set a coldframe over the plants the day before the first fall frost is expected. Close the glass on the coldframe by nightfall and place blankets or burlap sacks filled with leaves on top the glass to help retain heat.
Open the coldframe to vent during the day. Place a thermometer inside the coldframe and vent when temperatures inside the frame rise over 75 F for most cool-season vegetables. Alternately, vent when daytime temperatures outside the frame are over 45 F.