Outdoor Root Cellars
The Organic Garden BlanketThe earth holds a surprising amount of summer heat in its mass. If you can trap this heat with some kind of fluffy organic blanket — leaves, clean straw, sawdust or even banked-up snow — it’s entirely possible to keep soil from freezing for months longer than if it were left bare. In areas with mild winters, you can even keep soil soft enough to dig in year-round, allowing you to harvest snapping-fresh, cold-tolerant vegetables while everyone else is relying on food from the grocery store. To make handling the blanket easy, tuck your leaves or other material into recycled trash bags before you lay them over your root crops.
Vegetables that can be harvested when the soil is covered in snow include beets, Brussels sprouts, cabbages, carrots, endive root, Jerusalem artichokes, kale, leeks, parsnips and salsify. After the first hard frosts mark the end of the growing season, nestle your crops under an organic blanket and they’ll keep reliably down to about -3°C/25 degrees Fahrenheit. They might even be OK at somewhat lower temperatures, depending on snow cover, the soil moisture level and the variety of vegetables involved. (You’ll know the weather has gotten too cold if the vegetables are soggy and soft when they defrost.)
The Trench Silo
Start by digging up your beets, carrots, parsnips and other long-keeping root crops, cutting the tops down to about 1 inch. Next, dig a trench 6 to 10 inches deep and 18 to 24 inches wide. Replant your vegetables close together in the bottom of this trench, replacing the soil around them and heaping it 6 to 10 inches above them, burying the crops completely with soil. A variety of crops can be kept in the same trench.
The temperature and humidity levels below ground are perfect for preservation, so you will be able to harvest crisp, living produce from your trench silo right through winter and into spring. Because your vegetables will be deeper underground after you replant them in a trench silo, they’ll be better protected against winter temperatures than if you simply covered them with an organic blanket.
If you live in a region that has cold winters during which the soil freezes too hard to dig, you may have to leave your root veggies cozy in their trench until spring before harvesting them. If your climate is mild enough to allow you to dig into the soil year-round (perhaps with the help of an organic blanket over the trench), you can harvest as needed throughout winter. In that case, be sure to mark the ends of your trench silo with a couple of stakes so you can find it easily after snow starts to fall. When you’re ready to harvest something, simply dig down, take what you need, replace the soil (and blanket, if you’re using one) and move the stakes so you know where to dig next time.
The Hole-in-the-Ground Pit
The first parameter is a location with good drainage. Sandy soil is usually best because the particles that make up the soil are large, allowing water to drain quickly by gravity. Find a slightly elevated spot if you’re able, as the slope will encourage surface water to run away from your pit as it percolates downward.
If your wintertime temperatures drop below -3°C/25 degrees, dig your pit deep enough so that your stores will be entirely below ground. As you dig the hole, flare the sides to keep the soil from caving in. You’ll need more flare to stabilize light soils, less for heavier ones. Line the bottom and sides of the hole with straw or dried leaves. Cover the hole with a three-quarter-inch-thick wooden lid, and then cover the lid with soil.
If your winters are mild, you can make the hole shallower and store some of the produce aboveground, protecting it with straw or dried leaves underneath a 6- to 8-inch layer of soil. In this case, you won’t need a lid, but you will need to create a straw chimney for ventilation. To do so, hold a bundle of straw vertically in place as you add soil over your pile of root crops. The continuous channel of straw through the soil cover will allow moisture and gases to escape. Place a flat rock or a heavy board on top of the ends of the straw chimney that protrude above the soil cover, which will shield it from rain. It’s easier to dig and draw produce out of a shallow pit than a fully subterranean one, but keep in mind that a shallow pit won’t be as frost-resistant.
The Garbage Can Cellar
Keeping water out is one of the challenges of a hole-in-the-ground pit cellar, but using a garbage can will help. Dig a hole slightly larger than the diameter of the can and deep enough so that the can’s lid will sit 6 inches or so below the soil level. Set the can inside the hole, then layer in the veggies with some straw or dead leaves. Set the lid on the can, use a stick to pack soil all the way down into the gap around the outside of the can, and then flare the soil out at a tidy angle around the opening. Long-keeping root vegetables will live happily down there, even in the coldest weather. Good storage apple varieties will too, but keep your veggies separate from them. (Apples release ethylene gas as they ripen, which will shorten the storage life of vegetables.)
Cut a couple of 2-inch-thick pieces of extruded polystyrene foam slightly larger than the diameter of the lid and place the foam on top of the can to keep out frost. Cut another circle of three-quarter-inch-thick exterior-grade plywood to about the same size and place it over the foam, with a stone on top to keep it securely in place.
This technique also works well with other containers — such as an old chest freezer or a wooden barrel — buried in a similar fashion.
The Old-Fashioned Root Clamp
A root clamp is an elongated outdoor pile of produce that’s protected against frost, and it’s a good way to store large quantities of root vegetables in all temperate regions except those with hard winters. To make a root clamp, mound your vegetables on a bed of straw, cover the pile with more straw, then cover everything with a layer of soil, shoveled on and packed down.
Start by sorting your freshly dug crop — any long-keeping root vegetable can be clamped, though potatoes are the most popular — removing small and damaged pieces for immediate use. Place a 6- to 8-inch-deep layer of straw on the soil, then heap your produce on top as steeply as you can, making the pile 32 to 40 inches high. As you work, create horizontal tunnels of straw that extend beyond the edges of the pile every few feet. As in the hole-in-the-ground pit, tunnels will allow excess moisture and gases to escape from the clamp.
With your vegetables mounded, cover everything with 6 to 8 inches of straw before grabbing your shovel and capping the pile with 6 to 8 inches of compacted soil. Be sure to leave the straw tunnels exposed near the ground, and create chimneys of exposed straw every few feet along the top of the clamp. The idea is to allow a slow upward flow of air to pass through the pile, venting off excess moisture and keeping things fresh while still allowing the clamp to retain enough of the earth’s heat to prevent freezing. Place a flat rock or a heavy board on top of each chimney to shield it from the rain.