In most cold winters areas, where the temperature regularly drops below freezing, it's not possible to grow many plants. A few like snowdrops, witch hazel and forsythia bloom, but it's not the time to plant them. Others like roses and perennials go dormant. Cold frames allow plants to grow in temperatures within a few degrees of frost but not much below 30 degrees on a day-to-day basis. If you want plants to grow in winter, grow them inside.
Cool Season Vegetables
Check with the agricultural extension service of the university near you for the average date of the last frost. Start seeds of leafy greens, lettuces, broccoli, cauliflower and cabbages six to eight weeks before that date. Most seedlings require consistent moisture and bright light. Keeping the pots on a tray makes them easier to water.
Cool Season Flowers
Pansies, stock, snapdragons and nasturtiums prefer cooler temperatures to bloom. Getting them started during the winter gives them a longer time to bloom in spring before the summer heat hits. Start them as you would cool season vegetables.
Plan ahead in late summer for growing tomatoes all winter. Start a few tomato plants in 1-gallon size pots in August. They'll most likely be producing, or be ready to produce, in October. Bring them inside before the first frost. Pollinate the blossoms yourself by rubbing a cotton swab over the newly opened blossoms or use a commercial blossom set product. Other vegetables to grow inside are cucumbers and leaf lettuce. Choose the bush variety of cucumbers if you don't have a lot of space. Or train the vine type up a trellis in front of a west or south window.
If you have a sunny kitchen window, set up an herb garden in pots. You'll have fresh herbs ready to snip all winter long. Herb plants are often available in grocery stores in the produce section and as starter gift boxes during the holidays. Rosemary, oregano and parsley are easy to start from seed inside. Use the herbs often to keep them bushy. If you're growing tomatoes during the winter, grow some basil as well.
There's a wide variety of flowering houseplants to choose from including African violets, orchids, succulents and cyclamen. Choose plants based on your lighting requirements. For example, African violets don't require bright direct light while, gardenias do when inside. Another alternative is to force spring bulbs inside during the winter. You will need to prechill tulips, hyacinths and crocus in the fridge--not the freezer--for 12 weeks before planting.