If you are wishing you could extend your gardening season but think it’s all over when the first frost hits, you have a whole world of winter gardening awaiting your growing pleasure. You just need to pick the right things to grow, to give them adequate protection, and to expect them to grow a bit more slowly because they’ll be getting less sun.
It may surprise you to know that one of the nation’s most famous four-seasons farms is in Maine. Granted, Maine’s coastal waters keep it from being as cold as, say, Minnesota, but it still gets awfully darn cold. The folks at Four Seasons Farm are real experts, but you can get a start on small-scale winter gardening here with me. Let’s get first to the seed.
For winter gardening, you obviously need to pick vegetables that are ordinarily geared for colder weather. Do not expect to grow anything that seed packets label “tender” without a lot of energy-intensive protection, which is not sustainable. That means you will most likely not be successful growing peppers, squashes of any kind (winter squash isn’t called that because it grows through the winter but rather because it keeps through the winter), cucumbers, melons, or most beans. You can, however, grow everything in the cabbage and broccoli family 
, most greens, many root crops, and certain herbs. For example, basil and parsley prefer warm weather, but chervil and cilantro like it cooler. If a seed guide recommends early spring or late summer planting, you may be able to get a winter harvest. If anything requires pollination, expect to do it yourself with a tiny paintbrush, because the buzzies who usually do the job won’t be out and about.
Now let’s talk about protection. Winter gardening requires you to cover crops through the coldest weather. If you only have an occasional light frost, you can do the job with old sheets. If you expect regular freezing weather, begin by adding mulch around tender plants and especially root crops. Then cover with plastic or glass, being sure that the plants do not touch the covering; plants that touch the covering may freeze. Building raised beds make covering much easier.
Here are plants in a raised bed in early February, having started their life in early January and survived several nights down to almost 0 degrees F.
I built the raised bed to fit an old window that my neighbor was replacing. I placed the window directly on top of the wooden frame (made out of scrap wood). On warmer days, you can slide the window back or use a small piece of wood to raise one end and let the cold frame vent hot air.
This pup-tent style grow house can be found in many forms on the internet and works well if you need something taller: 
Note that I did not remove ice and snow after a storm. Those are going to be a consistent 32 degrees F, so if the air temperature is much colder, the snow actually serves as a blanket. Just know that it reduces light, so you need to get it off eventually.
That brings me to my last warning on winter gardening. You’ll find that crops grow much more slowly in the winter. They also may germinate less well, so you may want to overseed. (You can always eat the thinnings, as we did from the cold frame shown above.) Still, you’ll find that the plants will take off as soon as the sunlight starts coming back, giving you an early spring harvest that will be the envy of your gardening neighbors. 
