Planetary refrigerators

It’s getting cold again, and while I look forward to seeing more days when I can work outside without bundling up, the cold is useful for many things. For one thing, it’s as cold as a refrigerator outdoors, and that means you have less need to spend electricity on a refrigerator inside. In fact, you can do the same thing year-round, simply by keeping some of your food underground.

Look over the houses of County Kildare and you will see many garages, tool sheds, trampolines, storage units and even swimming pools, but you are unlikely to find many root cellars, or even many people who are familiar with the term. Yet root cellaring seems to have been practiced in most times and places, and even, in a sense, by animals who bury their food. It is a zero-carbon, zero-electricity, low-cost way to keep roots and other foods over the winter, simply by using the planet as your refrigerator.

Root cellars can take many forms, but they all work on the basic principle that vegetables in the right conditions stay alive, so they do not spoil, but also do not continue to grow, ferment, seed, bolt or any other plant activity. Since the temperature underground changes little throughout the year, this usually means keeping them partially underground and well-insulated.

Perhaps the easiest things to root cellar are the roots the name implies – carrots, potatoes, parsnips, beetroot, celeriac, turnips and so on. Many vegetables and fruits can be stored, however -- krauts like cabbage, broccoli, cauliflower and kale; onions and their relatives leeks and garlic; fruit like apples and pears; herbs and even salad greens. Most of the vegetables come from late-season plantings, when the crops are ripening at the latest possible moment before they must be stored for winter.

You can keep potatoes or carrots in boxes of earth, sand or sawdust; I did this last year with beetroots to see how long they would keep, and was delighted to find that they remained firm and delicious after six months. After a year they began to get a bit wrinkled on the outside, like a raisin, but not rotten --- and I can attest that they were still quite edible.

You can make a fort out of straw bales, as a child might do with pillows, and keep food cool inside. You can poke two pegs in the ground at either end of a crop row, pull string taut between them, and wrap plastic over the rope to make a long small tent. Some people have buried broken refrigerators and used them to store food – a literal electricity-free refrigerator, although of course you might want to have the chemical fluids drained first, in case they leak into the soil.  

Many potatoes and other vegetables can be piled into mounds and covered with earth and straw. Mounds should not be dug where water puddles, and while some gardeners dig out a mound first, we who live in the Bog of Allen might fine it safer to simply start on the ground level. The triangular pile should probably not be more than a metre high, to avoid the weight of the higher vegetables squashing the lower ones. Some kind of ventilation – a column of straw, a pipe -- needs to be put through the middle of the stack. The pile of potatoes is covered first with a layer of straw – 15 to 30 centimetres -- and then a layer of earth about half as thick.

Here in the bog we can’t have cellars, but those who do can turn it into a refrigerator for food storage. Put shelves in the corner, to maximise the cool space nearby, ideally on the north side (in the Northern Hemisphere). Have a pipe go through one of your window spaces to let the damp escape, with each end covered in screen to keep pests from using it as a highway. Even better, install two pipes at opposite ends, to allow as much air circulation as possible. You want to keep the air cool but dry and circulating, as much as possible.

You could also dig a pit about a metre deep and a few metres across, lean two wooden walls against each other in the pit to make a triangle, nail them together, and cover the top with a thin layer of earth. The result is a root cellar with an insulating earth and grass roof that can be a walk-in refrigerator during the winter months.