By Kristen Hannum –
Rick Visser’s 17 raised beds, small greenhouse, mini orchard, compost bins and shed are all important to the garden at his Longmont home, but it’s his cold frame — a 10-foot-long, 30-inch-wide bottomless box with a tilted and hinged window cover — that gets him really animated.
Part of that, no doubt, is the joy of serving Sierra crisp lettuce from his garden for a New Year’s feast. November, he says, is a great month to get a cold frame started.
Visser built his cold frame based on master gardener Eliot Coleman’s design from the book Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
Coleman wrote that the Parisian gardeners of the 19th century were his inspiration for building cold frames. The maraîchers (market gardeners) fed all of Paris and exported to buyers as far away as London with up to eight crops a year. Lettuce in February! Cucumbers in May! Their secret? A variety of cold frames and cloches, those bell-shaped glass covers for plants, plus a lot of manure.
Whether you want to get an early start on summer for your vegetables, to overwinter your tender perennials or to truly harvest vegetables all year round, a cold frame may be in your future.
The first step is deciding on its south-facing location. A deciduous tree shades Visser’s cold frame in the summer and offers sun in autumn, winter and spring. His cold frame is tucked against a cream-colored shed that reflects heat toward it for warmth.
Shades protect winter plants.Once you know where your cold frame will go, prepare the bed it will sit upon. Visser dug down 8 inches, carted off that layer and then broke up the dirt another 8 inches down. He laid compost on top of that, and then topped the bed with about 3 inches of potting soil. Some gardeners also advise laying drainage gravel below the cold frame’s soil bed.
If you build your cold frame yourself, don’t be tempted to think that taller is better. Too much height makes for too much air to keep warm under its window-like lid.
In addition to his long cold frame, Visser also makes use of an inexpensive, store-bought one. “We ate a lot of food out of that two-by-four frame,” he says. “It’s a good fallback for someone just getting started with the idea.”
With cold frames, take into account the necessity to keep them, well, cold. Or cool. Left unvented, temperatures inside a cold frame can soar to 100 degrees and your plants will die as fast as they would if left abandoned in the car on a summer day. Automatic temperature-sensing vents are inexpensive, but Visser vents his cold frame manually.
“Life calls for attention,” he explains. “Daily, caring attention. When I go out in the morning to open the cold frame, it’s a delightful thing. It’s no different than taking care of a child or a pet. You don’t say, ‘Oh, I don’t feel like milking the cow today.’ And there’s a deep feeling in that.”