Grow longer with cold frames
Cool nights and decreasing daylight are signals that the growing season is almost over, but that isn't true for some tasty vegetables. With a little protection and some wise plant choices, you can harvest healthy, crisp vegetables well past the first frost, which comes to Medford around October 17.
Compost amended soils and good drainage are key to successful winter gardening, says Ester Lee, associate at Medford's Grange Co-op. Roots starve for oxygen when the soil is too wet for extended periods of time, killing the plant. In our area, raised bed gardening is ideal for managing drainage problems. Denny Morelli, owner of Denny's Community Farm and Garden Resource in Gold Hill, suggests layering 2 to 4 inches of nutrient rich compost onto existing beds to insure a good growing medium for winter vegetables and plants.
To maintain a healthy growing temperature, locate your beds in a warm location against a southern slope, or south-facing wall or fence in full sun. Vegetables such as collards, corn salad, garlic, kale, leeks, onions, parsley, parsnips and spinach can survive to zero degrees so need no protection if they have good drainage.
If you've got a vegetable bed with tender fall vegetables like lettuce, broccoli, or radish, shelter your plants from freezing temperatures and rain to extend the harvest throughout the winter. To create a simple and satisfactory shelter, arch lengths of rebar or ½ to ¾ inch PVC across the bed, secure the ends in the soil, and cover these supports with 4-8 mil clear plastic sheeting to make a satisfactory shelter. Use inexpensive spring clamps to keep the plastic from blowing away. Any type of frame that keeps the plastic, fiberglass or glass high enough above the plant foliage will work. Plant parts that touch the shelter will freeze. Old windows and clear fiberglass can also be used as shelter material.
When temperatures dip below freezing on long winter, nights, extra heat may be called for. A string of C7 or C9 outdoor Christmas lights can be strung inside the frame of your shelter to raise the temperature by several degrees. Christmas lights disperse the heat better than a single light bulb. Your bed will be even warmer if you put an old blanket over the top of the shelter. Remember to vent the shelter on warm, sunny days, so your vegetables don't get overheated. Some varieties of fall/winter crops such as spinach and cabbage will bolt if they become too warm. Remember to water under the plastic as needed.
Ornamental gardeners can use cold frames for their benefit as well. Use these frames to temporarily shelter potted plants, such as geraniums, gerbera daisies, or other tender annuals to extend their bloom. You can still have these blooming for Thanksgiving, and maybe even Christmas.
In late winter, put potted bulbs into a shelter to force an earlier bloom. Hardwood cuttings of shrubs, roses and grapes can also be protected in these shelters, but don't use cold frames to overwinter things like lemon trees, bougainvillea, datura or other plants that need consistently warmer temperatures than cold frames can provide.
Modern plastics have made winter gardening much simpler. Take advantage of the Rogue Valley's relatively mild winters, and add a cold frame to your garden this winter.