It is said that native Australians were the first to develop the idea of the root cellar as a place to keep temperatures of harvested crops above freezing but below about 40 degrees Fahrenheit in order to preserve them. They also discovered the process of fermentation, and ever since the alcoholic beverages produced have often been stored in root cellars as well. But then, root cellars are also wine cellars.
There are endless ways to build root cellars, large and small, buried or above ground to store those typical root crops to maintain their quality as long a possible. Carrots, turnips, beets, parsnips and potatoes, and other root crops are typically stored there and the temperatures kept between 32 and 40 degrees Fahrenheit.
Root cellars have been fairly common in the northern part of America. By the age of 5-6, most young children in that part of the country have been asked to fetch an item from the root cellar, and to please remember to close the door before leaving. It is hard to forget the picture painted of a root cellar at the back end of a dugout sod house in Willa Cather’s classic tale of European immigrant mid-western farmers in “My Antonia.”
Root cellars were typically built into the far northeast corner of cold, humid, and unheated basements. The front and side parts of the squared off area protruding into the basement were often insulated whereas the outside walls were neither insulated nor covered with wood. In locations with extremely cold winters, however, a scaffold of two by fours against the wall covered with moisture resistant wall board was more common. Shelves were built along the back walls and set at least 2-3 inches away from the outside wall. A smaller set of movable shelves were often placed up near the door. This still left some floor space for baskets of harvested vegetables or fruits. There were no windows, but generally in/out ventilation pipes were built in to help regulate temperatures and to occasionally exchange the air, also giving the plant-derived ethylene gas a chance for escape. A small-watt bulb was placed above the center of the room or even near the door on a switch for two purposes: to see what one was doing, and to keep the room a little warmer in case of an extended cold spell. Occasionally, mouse traps with bait were laid around the room.
The temperature of the root cellar is often not uniform and onions, shallots and garlic may be placed near the warm ceiling as they will tolerate the warmer temperatures better. Cabbages may be hung upside down from the front of middle shelves. Potatoes, beets, carrots and turnips were placed almost anywhere. Canned good were stored here as well. However, as the metal lids may begin to corrode in a humid environment generally kept at 85-95% of maximum humidity, the canned goods can be partly protected by keeping them in boxes with some protective desiccant at the bottom. Alternatively, you can divide the room and make part of it far less humid, especially the part accessible from another entrance. But, remember that the real virtue of long term cold storage is simplicity. Cold root cellars are often good places to store wine as well. In that case one should remember to make a place for the wine as well as fruits and vegetables. In either case it may be worth equipping the root cellar with both a thermometer and with a hygrometer, in the latter case to measure relativity humidity.
There are many different kinds of root cellars that may be built outside away from the house or adjacent to it. They may be built below the soil line with some difficulty, or they may be built above ground and surrounded on all sides, except for the door, by rocks and added earth which acts as effective insulation. You still need a ventilation system and a thoughtful insulation of the roof. Room enough for a few barrels of water inside such a root cellar can function effectively as a thermal buffer, and if the water barrels are all of the same height, a board can be placed over them, or even build in additional shelves there for canned goods or for baskets of vegetables and fruits. A gravel floor is often highly suitable for such root cellars.
There are endless designs for root cellars on the Internet. The simplest one I have seen is that of a large covered garbage can, lowered a small way into the soil (perhaps 6-8 inches). You then surrounds the can on all sides with a mound of rocks and soil, covering the can after adding vegetables for storage. After the cover is in place a heavy layer of straw is added over the top. This system does not have a sophisticated ventilation system and during a cold spell would be hard to get in and out of on a regular basis, but with care might more than meet someone’s needs provided those needs were modest. Clearly the whole can could be emptied quickly and the vegetables placed on a table in a cool area in the house or on an unheated porch until an expected bitter cold spell had come and gone. Indeed, it is worth remembering that a cold unheated porch may be all the root cellar some need. A few baskets of vegetables protected by a small covering tarp in a long, modestly cold, but not bitterly cold, winter may be all that you need.