When you think of gardening, you might think of Spring planting, Summer weeding, and Fall harvesting. The word WINTER usually doesn't come to mind, but with Colorado's unusual weather patterns, you really have to learn to think creatively.
Cool season crops like radishes, bok choy and other greens are typically planted in very early Spring and harvested before it gets hot, the plants bolt and then go to seed. In Colorado, early Spring is when we are getting our worst snow storms, arctic air blasts and blizzard conditions. Once that passes we jump right in to 80º-90º temperatures with out batting an eye. Those tender cool air loving plants don't stand a chance.
Planting in Winter makes more sense with our wacky Spring weather, but you can't just throw seeds in your regular garden bed and expect things grow in the cold. Low light, high winds and cold night time temperatures mean your plants wont sprout. If by some chance some do, they will die quickly. By planting in November or December, most likely the local birds will dig up and eat your seeds and not even bother to say "thank you!". With a little planning and recycling you can fool Mother Nature and actually enjoy some fresh homegrown vegetables while everyone else has to go to the supermarket and pick through flavorless, expensive imported produce.
This doesn't look like much, but this simple piece of plastic covering a garden bed and held up by 2 bent PVC pipes holds a little secret...
These little Chinese cabbage plants were sown in October right before our first frost.
On the other side of the grow tunnel there is more Chinese cabbage, a few spinach plants leftover from Summer, and a cilantro plant that snuck in. No doubt it was a seed from a plant that bolted during the hot Fall weather.
The key to this growing tunnel is not just the plastic sheet cover, but those recycled 2 liter bottles you see bordering the growing bed. These bottles filled with water provide important thermal mass. Thermal mass absorbs heat during the day and then slowly releases the heat in to the tunnel at night. Without the thermal mass, you might be able to extend the growing season a bit during Spring and Fall, but your odds of keeping plants alive when it gets below 20º at night are not good. The combination of the 2 liter bottles and the plastic cover create a nice little microclimate that allows some plants to grow completely out of season.
The growth rate of Winter vegetables is going to be much slower than if you planted them in warmer weather. But by already being sprouted and growing they are poised to take off once the days start to lengthen.
Any plants that like cooler weather can be used in a tunnel garden, but Chinese greens are especially suited to this type of growing method. Thinking of trying your own Winter gardening experiment? Here are some good resources to get you started...