Portable: Gar Wang, an artist and renowned gardener (and former writer of a gardening column in Dirt), has a handful of cold frames scattered around her Warwick property. At least one is portable, with a frame made of wood furring and a Plexiglas top. In early spring, Wang uses the cold frame to acclimatize potted seedlings; when fall brings its bite, she carries it to a garden bed to protect plants that thrive late in the season, like carrots, certain lettuces, beets, mustard greens and pan di zucchero chicory – an heirloom that we’d never heard of either but will be trying out next year.
A caveat: Wang originally used a recycled window for her cold frame. After she discovered she was suffering from lead poisoning, she bought a simple test at a home improvement store, whose strips you rub on surfaces to detect lead. She found that the paint on the window, under which she was growing her food, was the culprit.
(+) Does double duty hardening off seedlings in the spring and protecting plants from killing frosts in the fall. (-) Plexiglas, while a good hardy lightweight option, can warp under weight, making the cold frame less effective.
Lean-to: Wang’s row of permanent lean-to style cold frames built up against the south side of her house stay the warmest of all. The house’s concrete foundation, which stores heat over the day and releases it at night. In here, Wang transplants late survivors from her garden, scatters leftover seeds, and leaves self-seeding volunteers that hitch a ride in her compost, like chickweed, which most people think of as a weed but is super nutritious, and claytonia, a cold-hardy salad green that we’ve suddenly been hearing about everywhere.
This style works so well that on November 18, after nighttime temperatures had dipped well below freezing, a happy looking hot pepper plant was still going strong. Hot peppers are supposed to die when exposed to temperatures below 50 degrees. The plant was surrounded by sheep’s wool, a new mulching technique Wang was trying out after she’d helped sheer a friend’s sheep.
The cold frame where the pepper lives is topped with the crème-de-la-crème of heat-trapping material, used in professional greenhouses: double wall polycarbonate sheets, which trap a layer of dead air that acts as additional insulation. Wang got the stuff from a friend who was taking down a studio. She now kicks herself for being shy and taking only a few pieces. It’s expensive, and hard to find in small quantities.
Permanent cold frames like this one have their advantages, but animals will eventually find a cold frame that stays in one place. “If you’re going to go to the trouble of building one, put a half inch of galvanized hardware cloth under the frame, attached to the sides, to prevent voles and moles from digging in,” said Wang.
In the summertime Wang uses these frames for plants that love heat. Some plants spend season after season in this protected spot. Two parsley plants have grown into what looks like a massive shrub, and there’s Swiss chard that’s a year-and-a-half old. During the hot weather, the chard had some signs of leaf-spot, said Wang, but most fungal diseases are killed off by cold. It’s actually doing better now.
The cold takes care of most insect pests, too. The one bug that feels at home in the dry, cold conditions found in a cold frame is aphids, which Wang knocks off by squirting with water.
(+)The mass of your house provides temperature control. You have one less side of the frame to build. (-) Moles and voles will eventually find and tunnel into a stationary cold frame, so it’s worth fortifying the bottom and sides with mesh hardware cloth.
Hot bed: More than 2,000 years ago, Chinese peasants built raised beds filled with three feet of fresh manure under the topsoil, which, without so much as a cover, produced enough heat to extend their growing season by a month. Rotting poop gets hot —something Americans have had the luxury of being able to forget.
Wang noticed as much. The first year after she built up the soil in her lean-to cold frames with fresh horse manure, “it was incredible,” she said. “We started late that year, the end of September,” and yet the plants, warmed by the manure’s slow release of heat, did well. On top of the manure goes a layer of well-rotted compost. The plant roots never touch the manure, which would burn them.
(+) A natural way of adding supplemental heat that also improves the soil when it breaks down, and a good way to get rid of poop piles if you have livestock.(-) Fresh horse manure, ideal for hotbeds, is notorious for bringing weed seeds, part of the reason that Wang only used it the first year. Now she barters with Lowland Farms for cow manure.
Straw bale: After he’d harvested an “eh” crop of corn, Steve Moriarty planted cold hardy mesclun salad, rocket arugula, turnips, and kale in early September. He surrounded the bed with straw bales that had been pulled from a maze, and covered it with a sheet of painter’s plastic weighed down by wooden two-by-fours. The morning after the season’s first snow, the bed was full of greens. “It survived the first snow,” said a mostly satisfied Moriarty. Snow, however, was weighing down the plastic so that it crushed some leaves. “I’m going to have to add the hoop,” he said — meaning he wanted to turn it into a low tunnel (see next page). To prevent sagging, you could also use a storm door or window, or rigid plastic to top the bales.
(+) Cheap, totally natural, requires no construction. Come spring, you can use the straw for mulch or to contain, and eventually become part of, a compost pile. (-) The straw that Moriarty acquired was sprouting grass, which he said is not supposed to happen. This meant that there were weed seeds in it, and introducing weeds to your garden is something you want to avoid.
You can feel warmth come off the soil when Wang uncovers one of her tunnels on a near-freezing day. The photographer hurriedly snaps pictures; Wang needs to replace the cover quickly before the sun’s trapped heat escapes. It’s 3pm, and the sun is fading. These jungles of celery, Italian dandelions, lettuces, radicchio, collared greens, and purple peacock broccoli (a cross between kale and broccoli) will need this heat to get through the night.
Wang uses one-inch water pipe to create the hoops over which she drapes different types of salvaged plastic. The pipe is attached to the outsides of her wooden raised beds with electrical conduit clips. Moriarty uses PVC pipe for his hoops, sticking the pipe into the soil just inside the frames of his wooden raised beds. After the first snow of the season, he decided to add hoops to his long narrow straw bale bad, but when the next snow came it appeared he may not have made them quite hardy enough: “I don’t know, the front end of it kind of fell in. The arugula and turnips are fine,” but the lettuce, it seems, absorbed too moo much water and burst. “The greens part, I’m letting it recover.” Even without doing it perfectly, though, Moriarty had arugula and turnips, beets, and some lettuce and kale, on December 5.
“My whole take is you don’t need to invest in a fancy expensive greenhouse to do this. You can keep it simple and be a small-timer. You have to be in tune with the type of plant that will do well and the location. You don’t want to fight going uphill,” said Wang.
Moriarty never waters his plants in the winter; the condensation, he says, is enough. Wang waters only when the soil feels dry, at most twice a month.
When temperatures drop below 20, particularly if it’s late in the winter when she’s already lost many of her plants, Wang sometimes adds a second layer of protection in the form of a floating row cover over the plants.
The trickiest thing about low tunnels is not keeping plants warm, but keeping them from heating up too fast, said Wang. “A lot of these plants can handle freezing. It’s the next day. You have to not expose them to high heat because the problem is, I think, that the cell wall may burst.” So on a warmer day after a frost, Wang uncovers her tunnels slowly, a little bit at a time, to avoid shocking her plants and to let them recover.
Winter gardening may not be for the weekender. It’s more hands-on than summer gardening in some ways, but the considerable upside is: no weeds.
Upside: Less expensive and can cover a greater area than cold frames, effective even if not done perfectly.
Downside: Awkward to uncover, especially when covered in snow, making them inaccessible sometimes; vulnerable to collapse under the weight of snow; you have to manually vent off excess heat.
COUNTERTOP CROPSIf you don’t like going outside in the cold, all is not lost. You can still grow all sorts of food indoors, almost as well as you can outside, from herbs to lemons (we haven’t had success with lemons yet, but our Meyer lemon tree is flowering beautifully in the bedroom.) If touching dirt isn’t your bag either, you can still grow food! Sprouts are for you.
You need: a glass jar, cheesecloth or a cloth napkin, a rubber band, and a tablespoon of seeds -- broccoli or pea work well. Place a tablespoon of seeds in the jar, cover it with the cheesecloth or napkin, pour water into the jar, and place the jar at a 45 degree angle in a basket out of the light, so that the cheesecloth-side is facing down and any excess water can drip out. The top of the fridge works nicely as a place to store your jar(s). Pour water into your jar, then drain it, two or three times a day. In a few days, the seeds will sprout, and become a ball of green shoots. The day before you want to use them, place them in a sunny spot to let them turn green.
Upside: You don’t have to go outside and there’s little to no start-up cost if you have leftover seeds. Most winter growing is slow-to-nonexistent since plants are just surviving until it gets warm again, but sprouts provide instant gratifacation and are fun for kids.
Downside: Remembering to water your sprouts twice a day is one more chore.