The year round availability of fresh produce at supermarkets in this modern society has pretty much eliminated the use of the historic age-old root cellars. It appears that all that remains of its existence are the fond childhood memories of that deep dark scary place known only to a kid as a fort! However, as more people are reverting back to the basics of home gardening, there is a revitalization of the good old-fashioned root cellar. It has been reborn into an indispensable addition. You can easily build a root cellar in your very own basement, outbuilding or even as an outside pit. This article covers root cellars and is not inclusive. It should be shared with Kali’s Store Garden Produce Series #1-10. Store Garden Produce #10 covers root barrels, outbuildings and storage pits.
In the root cellars heyday, our ancestors used cold storage to keep food fresh when temperatures made it advisable for produce to be stored underground. Root cellars were the basic equivalent of today’s refrigerators. Nowadays, those dedicated to eating locally often preserve foods at the height of the season when produce is less expensive and more nutritional compared to buying food in the dead of winter when produce is an expensive commodity.
Root Cellaring: A root cellar is any storage area that uses the earth’s natural resources to cool, insulate and humidify the produce stored within. They are earth-friendly, non-polluting and require no electricity. To work properly, a root cellar must be able to hold temperatures of 32º to 40º F and maintain a relatively humidity level of 85 to 95 percent. A good quality hygrometer will check for humidity and temperature levels within various locations within the home, whether it be an unused storage room, basement or back porch. While the ideal root-cellar combination for fresh foods is low temperature and high humidity, the worst situation would be high temperatures and high humidity. This situation nurtures bacteria, mold and yeast. Therefore, a root cellar requires high humidity only for its ability to maintain freshness. Low temperatures (above freezing) are then needed to counter balance the bacteria and mold problems created by high humidity. Cool outdoor air circulation is also a requirement to regulate the conditions of the stored produce.
Maintaining Proper Humidity Levels: The main culprit for shriveling of produce in storage is low humidity. A dirt, sand or gravel floor is the best option for maintaining proper humidity control as well as for proper drainage. To raise the humidity of the storage air, the floor can be sprinkled down. Gravel floors provide the best “humidifiers” in this instance, especially if the gravel is several inches deep so that it is able to hold some water at the bottom. While most produce like moist conditions, standing water must be avoided. It will quickly decay your contents. Assess your own specific situation. Homeowners in the south might even consider installing a cellar sump pump or other drainage alternative if you happen to have a high water table.
For dirt or sand floors, place water in shallow pans under fresh-air intake vents to increase humidity levels. You can also pack root vegetables in damp sawdust, sand or moss to reduce surface evaporation. Covering food with dry burlap or towels can absorb some of the moisture in the air. If the air becomes too dry, dampen burlap cloths or pack root vegetables in wet sawdust to help increase humidity levels. Use your hygrometer daily!
Some root cellars wisely include two rooms, one with and one without a concrete floor. Concrete floors provide slightly lower humidity levels and are typically utilized in basement root cellars. Concrete floors are best when storing dry goods, grains, beans as well as some fresh foods such as pumpkins, onions and squash. In addition to proper temperature and humidity, all fruits and vegetables must be kept in a dark, ventilated environment. Produce must not be allowed to freeze and should be protected from rodents such as mice.
Maintaining Proper Temperature: The first consideration to provide longevity to root vegetables is to lower the storage temperature to 32° to 40° F (0 to 4 C). The goal of storage is to keep produce in a dormant state. Temperature can be regulated using 2 types of a ventilation system to the outside, either through one or two windows or by using 2 separate venting pipes. Both options allow cold air in and warm air out. Without proper ventilation for air circulation to control temperature, your stored produce will spoil. You don’t want a strong draft; however for this will remove moisture from the produce.
Cellar Ventilation: You need to install two pipes vented to the outside; one at the lowest point of the room and one at the highest. Both pipes should be a minimum of 3 inches in diameter. Cool air is denser than warm air and will collect in the low areas. Anytime the air outside your root cellar is cooler than the air inside, the air transfer from one pipe to the other will allow a heat exchange: cool air is drawn in while warm air is vented out. As outside temperatures fluctuate, you will be able to maintain continuous airflow to regulate the temperature as low as possible. Sites that include at least two windows on opposite sides of the root cellar are the least expensive to maintain and are more desirable in creating proper ventilation, particularly if the room is divided for separate dry storage goods.
The warm air pipe can be vented out the window, equipped with a elbow, at the highest point while the cool air pipe can go through the wall at any location just as long as there is an elbow attached to a length of pipe running down the inside so that it ends up about a foot from the floor. The elbows should be loose fitting since you want to be able to rotate the elbow toward the incoming wind…or direct it away from it. An alternative is to just add blast gates to each pipe. The two vents or pipes will create a siphoning effect. When the temperature outside goes below freezing, one of the gates or valves should be closed or turned from the wind. You will receive reduced venting but it will keep the produce from freezing. If the outside temperature goes below 32° F or 0 C, the freezing level, you’ll need to partially close both valves. Make sure to seal the wall or window around the pipes with aerosol insulating foam. This will fill in any gaps or cracks. Once it sets, it does a great job of holding the pipes in place. A finishing touch is to fasten a rod as a handle for each blast gate and run it through the outside wall of your cellar. This way you can open and close the valves as well as see the valves in their position without having to open the door to release the cold air. Additionally, shade the windows in a way that will prevent light from entering the cellar. Only a small amount of heat is necessary to prevent subfreezing temperatures. A light bulb left on during the coldest days provides just enough heat to keep the air above freezing. However, if you do keep it on, be sure your produce is covered with heavy cloth as protection against light and condensation, especially for potatoes!
How to Make a Cellar: You will need to consider the location of your root cellar. Some root cellars are built into hills and buried on three sides with a normal, walk-in door on the unburied side. Others are completely buried and must be entered by stairs often accessed through a door in the ceiling. If maximum coolness is a priority, as it will be in the south, then bury the cellar completely. As an alternative to a ceiling entrance, a stairwell can be dug just outside a cellar wall with a landing at the bottom, where an insulated door can be installed leading into the cellar. Keep that door out of the sun and away from any hot summer breezes. Too large of a room can become unstable over time. It may be better to build more than one if you need more room. Site your underground room in a place away from drains or other areas that may trap water. You need a good roof that doesn’t allow moisture to penetrate the cellar. It also needs to be structurally sound in order to cover the roof with at least 2 feet of soil. Dirt is the cheapest insulating material available; so do not skimp on adding more dirt. When the cellar is completely covered, scatter grass or flower seeds. Mint makes an excellent groundcover. Mint grows vigorously and produces a thick and binding root system to hold the soil in place.
When choosing a basement location, consider partitioning off the farthest northwest corner, preferably closest to the sump pump for additional humidity and one located by windows for ventilation as discussed above. Avoid heat ducts and hot water pipes that would generate heat. It will provide the coolest, dampest, darkest storage area. If located near a furnace, you can easily patrician off a section for dry storage such as grains, onions, garlic, squash and pumpkins as well as being able to insulate the actual root cellar within.
Insulating a Cold Cellar: A space eight-by-eight feet should be plenty room for the average family The best method is to use the foundation walls on the northeast corner for two sides then build the other two walls in the basement with stud and board. Due to the moist conditions, you should make the walls out of 2X4s made of cedar or other rot-resistant wood for framing as well as some moisture-resistant wall board such as “green board” used in shower stalls. While the exterior walls do not need to be insulated, the inside partitions should have 3½” thick fiberglass insulation. Faced insulation should have the vapor barrier closest to the warm side of the storage. If unfaced insulation is used, a vapor barrier such as 6-mil thick polyethylene can be used. The ceiling also requires insulation and a vapor barrier. Then it is time to apply the foam aerosol insulation to any nooks and crannies. You want the room to be as air tight as possible.
Root Cellar Door: One customized feature worth noting is to construct a door in two pieces, called a Dutch door that splits across the middle. You are able to access the bottom door when temperatures are warm and the upper section when temperatures are cold. This way you can open the upper half to grab a few items without letting out the coldest, dampest air at the bottom of the root cellar. Double-doors or a small anteroom (fore-room) provide an additional degree of protection from temperature swings.
Cellar Rack: Keep in mind that lower shelves will be cooler and wetter, higher shelves will be warmer and dryer. Arrange and space your shelves to suit the items that will likely be stored on them. Wooden wall shelves, bins, and pallet shelving is recommended, as wood does not conduct heat or cold as rapidly as metal shelving units. Do not use aluminum shelving which tends to cause condensation. Although moisture is good, icicles or water droplets are not. When you place the cellar rack, do not let the rears of shelves contact the cellar walls, as this restricts air circulation. Air circulation is critical for minimizing airborne mold, so shelves should stand 1 to 3 inches away from the walls.
Store vegetables and fruits in wood crates or boxes rather than in bins. Slatted crates for better air circulation utilize space more efficiently than baskets. Use containers that have smooth inner surfaces. Protruding wire staples in baskets and hampers are particularly damaging to a crops outer skin. Lightweight tub buckets are good containers for harvesting as well as standard apple and lug boxes used for shipping tomatoes, grapes, and nectarines.
Vegetables that are piled together will generate heat. Only stack 2-3 layers within any one container. You will want to place some of the crops on the cellar racks while others can be placed on pallets on the floor–always rotate or “air” your crops accordingly. Some crops such as potatoes, apples or pears can be covered in straw or individually wrapped in newspapers to retard ethylene gas discussed in Store Garden Produce #8.
Root Cellaring Temperature & Humidity Chart Here!
Follow Kali’s Entire Series on Storing Garden Produce for Winter
Parts 1-5: Store Garden Produce For Winter
Store Garden Produce #6-Storing & Freezing Green Beans Types
Store Garden Produce #7- Storing Cherries – Freezing Apples
Store Garden Produce #8-Ethylene Ripening-List of Fruits & Vegetables
Store Garden Produce #9-How To Build A Cellar-Part 1
Store Garden Produce #10-More on Root Cellaring-Part 2
Kali S Winters