Cold frame small greenhouses utilize solar energy and insulation to create a microclimate within your garden. If you have harvested and eaten a salad of fresh greens in February, or have flowers blooming well past frost, you know the attraction of using cold-frame small greenhouses. Cold frame small greenhouses help to overwinter plants, extend the growing season, start seeds, and harden off plants.
For whatever purpose you want to use a cold frame, you need to keep in mind a few basic factors. First, some plants fare better in cold frames than others, with low-growing, cool-season plants being the best suited. Second, the type of cold frame small greenhouses you use dictates how much protection you can offer your plants. In all cases, the main conditions you need to monitor and control are temperature, sunlight, moisture, and wind exposure.
To keep a tender plant in a cold frame, cut it back as much as possible before the first fall frost. If the plant is not already in a container, lift and sink the root mass into a large plastic pot, with plenty of room for soil to insulate it. Pack the cold frame tightly with pots, and add leaves or mulch over the soil surface and into any significant air gaps. Make sure all the pots are well watered.
Once you have your tender plants stored in a cold frame, you will need to control the weather conditions to maintain a healthy dormancy. Keep the soil moderately moist but not wet; the plants won’t need much water over the winter and will rot if overwatered. They should not receive much sunlight, either, because this will encourage active growth. I like to use a white plastic cover on my cold frame as it limits the amount of light penetration and moderates spikes in daytime temperatures.
Temperature fluctuations can be harmful to dormant plants and should be minimized by venting the cold frame small greenhouse. As a general rule, if it’s 35°F to 40°F and sunny, you should open the frame partway, while at 45°F to 50°F, you may need to open it up entirely. Using a sunken cold frame or siting your aboveground frame near a windbreak offers much-needed protection from exposure. This is especially important for those plants that may retain some foliage in winter.