For those who don't know, a cold frame is basically a small un-heated greenhouse that relies on sunlight for warmth. Many gardeners use old window sashes for the tops. (Note: Beware of lead paint if using old sashes). Last year, we harvested greens until early January when a hard frost killed everything. While the weather was tough in the northeast this year, with snow on the ground from December until yesterday, snow is an excellent insulator. Several feet of snow kept the temperature in the cold frame just right for our crops.
Last week, once enough snow had melted, we looked inside and were pleasantly surprised to find spinach, swiss chard, arugula, mesclun mix, beets, carrots, parsley, and rosemary still growing. They're not the huge leafy plants we get in the late spring and early summer, but they're tender, local, and fresh. We enjoyed a lovely meal of brown rice and tilapia atop fresh arugula. What a treat in early March! Knowing they had planted and harvested the very arugula that arrived on their dinner plates, my kids ate every bite and wanted more.
If you think you'd like to try your hand at four season vegetable gardening, I recommend the book Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long by Eliot Coleman