Cold Frames, Row Covers, Hot Caps & Hot Beds

These three "season extenders" will give you a few precious extra weeks at the beginning or ending of the growing season that are really pleasing to gardeners who can't stand the idea of waiting ONE MORE MINUTE, or who have flowers and vegetables - especially lettuce -- that still have a lot to give near the fall's advancing chills.

            Cold Frame: This mini-greenhouse is fairly easy to build. The key is to get an old, used window, and some redwood, white cedar or cypress wood. Basically, a cold frame lets the sun shine in, and then traps that solar energy within the glass, to keep the soil warm.

            You make the headboard about 18" high, slanting down to a football 12" high for rain runoff. Saw boards to connect the two ends and support the window. Position the structure so that it faces south. You can line the bottom with black plastic and then put high-quality organic soil in place. Remember to open daily to ventilate, and keep it moist but not wet.

            You may be able to buy a precut polycarbonate and aluminum cold frame in a nursery supply store.

            Row Covers: Floating row covers are soft, white "garden blankets" made of lightweight material that moisture and light can permeate. They come in various weights, sizes and thicknesses. The lighter they are, the more light can get through, but then they aren't as protective against frost. Thicker covers can allow too much heat to build up inside, although thicker covers are better protection against frost.

            Put floating row covers on right after transplanting heat-loving plants in the spring, such as tomatoes, eggplants, broccoli, melons, cucumbers, cauliflower and strawberries. Remove the covers when the blossoms are starting to pollinate, or it's reliably over 85 degrees in the daytime.

            You can get plastic row covers, too, which are like tunnels supported by wire hoops. They usually have holes or slits in the rigid plastic to let a little rain in. They may not be as good for frost protection, though, and tend to generate more heat than floating covers. So they are a good idea for plants that really like the heat, including cucumbers, melons and eggplants, in the early weeks of the growing season.

            Some gardeners report that plastic row covers may increase yields by as much as 50 percent because they facilitate earlier germination and crop development.

            Hot Caps: The lowly milk jug gets center stage with this simple trick. Just cut the bottom off a 1-gallon plastic milk container and set it over a seedling plant. Leave the lid off for ventilation.

            Remember, hot caps are only for seedlings to get a head start on growth. If you don't remove them by blossom time, your plants might not yield as well. So think of them as a very temporary solution for early planting season protection.

            Hot Beds: Here's how to bring fresh lettuce to the table for almost all winter. This assumes you have already put together a cold frame. Well, in the fall, you remove all of the soil to a depth of two feet inside the cold frame, and line the dirt sides with 1" or 2" thick panels of Styrofoam insulation. You can build a wooden frame around the Styrofoam to brace it, if you wish. Shovel in an 18" layer of fresh horse manure and firm well (where do you get fresh horse manure? Drive out into the country, spot some horses, and ask the property owner!).

            Spread 6" of sand on top of the manure. You will want to put a soil thermometer in the sand. As the horse manure breaks down underneath it, and heat is released, the sand may reach over 100 degrees at its peak. Then it will gradually cool down. You can put flats of seedlings and pots of plants in the hot bed when the sand temperature drops below 90 degrees. The composting manure will continue to heat the bed for several weeks, even months. Once it's composted, you can re-adapt the structure as a cold frame again.