My cold frame and I have an on-off relationship: We are buddies in winter and strangers in summer.
Just call us foul-weather friends.
For six balmy months, I've given my cold frame the cold shoulder. Oh, I passed it daily on my way to the garden, but I never stopped to chat. Too busy. There were flowers to cut and vegetables to harvest from the main garden. So I ignored the sturdy little garden box that had sheltered my tender seedlings on frosty spring nights.
Now, as the big chill approaches, I am starting to cozy up to the cold frame again. It is a mini-greenhouse that will bear our salad greens for most of the winter months. Neither hail nor sleet can stop the cold frame from producing fresh vegetables while the main garden sleeps beneath a blanket of snow.
Winter drastically alters my gardening habits. Come frost, I abandon my 1,000-square-foot plot in favor of the cold frame and its six square feet of garden space. I exchange my Rototiller for a trowel. This is a humbling experience; I feel as if I have swapped a garden the size of a football field for a 6-inch clay pot.
But I adjust to the snug surroundings, thankful for a few precious meters of soft ground. The cold frame earns its keep well into winter, trapping the sun's heat, increasing temperatures within by as much as 25 degrees, and deflecting bitter winds.
When the weather outside is frightful, our meals remain delightful, accented by crisp fresh lettuce and glossy leaves of spinach that continue to grow inside the Plexiglas womb in our back yard.
Though immensely popular with gardeners in spring, the cold frame is often forgotten in fall, when its potential is greatest. A cold frame can extend the vegetable harvest by two months or more. Have you checked the cost, and taste, of store-bought salad greens lately?
A cold frame makes a great way-station in winter for tender potted herbs and perennials, as well as for biennial plants that were sown last summer. Use the cold frame to "force" pots of hardy spring bulbs. Use it as a root cellar to store onions and potatoes. Or get a jump on spring by sowing seeds of hardy annuals in the cold frame, just before the ground freezes. The seeds will germinate early next year, producing plants more robust than one can imagine.
The cold frame is a simple solar device and can be made easily from scrap lumber by anyone with minimal carpentry skills. I bought a prefabricated model and botched the elementary instructions. The thing worked fine once my wife assembled it.
My cold frame is lightweight, with clear plastic sides, hinged top panels and a solar-powered thermostat that pops the lid automatically on warm days, unless our cat is sleeping on it. The thermostat, or vent controller, is a deal at $40. Otherwise, you have to adjust the lid manually umpteen times a day to keep the plants inside from cooking. And who is going to quit work to baby-sit a cold frame?
One of the best ready-built models, made in Austria, is available
from the Kinsman Co. (River Road, Point Pleasant, Pa. 18950). Call (800) 733-5613 for a free catalog.
Do-it-yourselfers have constructed cold frames of wood, metal and brick, and covered them with old storm windows. Railroad ties and cinder blocks make crude but effective cold frames; so do hay bales fit snugly together. One enterprising gardener grew his winter greens inside an old truck tire covered with a thick sheet of clear plastic.
The slanted top of the cold frame should face south for maximum sunlight and to allow snow to slide off easily. Mine is 2 feet tall and sits against the house, next to the vent for the clothes dryer, which provides added warmth. On frigid nights, I surround the box with old blankets and hay (a cold frame works like a horse, it should live like one).
Good garden hygiene is essential. Disease spreads quickly in cold frames due to high humidity. Remove all sick-looking plants. Replace the soil every two years. Weed and water regularly, but let tap water cool first.
Check for insect damage, too. I've found aphids attacking my kale on 20-degree days. Of course, inside the cold frame, it was a day at the beach for the bugs.