Make a Cold Frame for Herbs

Enlarge Image Image Gallery Hay bales topped by old storm windows work as cold frames made from what is on hand. Photo by Paul Gardener

Gardening guru Eliot Coleman asserts that “the basic cold frame is the most dependable, least exploited aid for the four-season harvest.” I couldn’t agree more, whether you’re stretching the season for spinach, growing biennial flowers and herbs, or using a cold frame (also known as a winter frame) as a holding place for divisions taken from chives, sage and other cold-hardy herbs. In the fall, I often lift seedlings of catnip, lemon balm or feverfew as I find them, and slip them into a bed I can cover with a frame or low tunnel.

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You can also use a winter frame as temporary winter quarters for overwintering plants that suffer under heavy snow, such as lamb’s ears, or for small potted herbs you plan to share. Winter frames have so many uses that eventually you will want several of them.

Your cold frame can be as unique as your garden. If you already have raised beds, you can usually find a simple way to top one or two of them with a winter cold frame. The first version I ever used was rustic, to say the least: I attached pipe strips to the outside of a raised bed and used green branches cut from the woods for hoops. The bed-turned-winter-tunnel was covered with plastic and anchored with pieces of firewood. It was such a resounding success that my winter frames have multiplied like lemon balm, incorporating ideas I’ve picked up from other year-round gardeners.

You can build a bed topper from scratch, but it’s usually simpler to reuse storm windows or shower doors found at resale shops like those run by Habitat for Humanity. These three movable cold frame setups have won thousands of fans in a wide range of climates:

Storm windows of recent manufacture (less than 30 years old, thus unlikely to be contaminated with lead), with their screens intact, are a top choice for covering winter cold frames. In spring, when you no longer need the protection of glass, you can pop in the screens to create a lightly shaded spot, protected from hail, for hardening off seedlings or propagating divisions or rooted cuttings.

Shower doors with their hinges, frame and safety handles still attached. The thick, tempered glass of shower doors can stand up to heavy loads of ice and snow (or kids climbing on them). Shower door frame toppers are not easily blown about in the wind because of their weight. I have used a humble box built of 2-by-4s topped with an old shower door for five years, and I never run out of uses for it.