Growing Undercover

With the arrival of the first frosts comes the time for season extenders that permit gardeners in the Valley to continue harvesting right on up until Christmas and beyond. By judicious selection of crop varieties, coupled with the use of a coldframe or unheated greenhouse, backyard farmers can continue production at least until the days grow short around the winter solstice.

Some crops have varieties bred to be planted out now for overwintering. Cabbage, broccoli, Brussels sprouts, cauliflower, leeks and onions are often grown this way. Transplants moved into the garden now will grow slowly and establish roots during the winter, before providing an extra-early harvest next spring. We have had great luck, for example, with the leek cultivar 'King Sieg,' when grown this way, and with the cabbage 'Savoy Perfection.'

The best way to extend the season is with a coldframe. This can be a very simple arrangement of straw bales with a couple of recycled window sashes on top, or a factory built structure. While we like the convenience of a walk-in space, a traditional raised-bed coldframe with a slanted, transparent top facing the sun will grow plenty of veggies. Don't imagine that you will produce tomatoes or cucumbers with such crude equipment! You will, however, be able to enjoy delicious lettuce, green onions, and various other salad greens in abundance. The key to coldframe salad production is to choose varieties that grow quickly and lend themselves to cut-and-come-again harvest. Arugula not only reaches harvestable size in about six weeks, it can be cut at least three times. Compact-growing bibb and buttercrunch lettuces are great choices for coldframe cultivation. Leaf lettuce varieties, like Black Seeded Simpson, are good for cutting more than once.

Take measures to protect coldframe crops from slugs. The warmth of the frame attracts the mollusks, which should be deterred with copper tape or wire and lured elsewhere with poisoned baits in the vicinity  of the coldframe. Do not place bait inside the frame or you will invite slugs in! Aphids sometimes invade coldframes. Spray plants with insecticidal soap to help deter them, and be prepared to thoroughly wash your harvest. A drop of dish detergent in a sink full of cold water will eliminate the aphids from your harvest on the first rinse. Rinse the leaves at least two more times to remove soap and any stray insects.

Our best outdoor crop following the frost is 'Lacinato' kale. This dark-leaved heirloom shrugs off the coldest weather we are likely to receive here in the Tennessee Valley, and can be picked at will throughout the winter months. I have learned the importance of letting plants develop a good root system in the garden before the first frost. They should be started, therefore, in August and transplanted in September. After a month, you can begin harvesting a leaf or two from each plant as you wish to use them.

Time remains to plant perennial onions, shallots and garlic for the rest of the month. Cover the bed with a layer of mulch to help protect emerging shoots. If you already have these crops growing from an earlier planting, mulching them now will result in improved production next spring, by helping to moderate swings in the soil temperature.