Cool temperature, high humidity, good air circulation, and proper ventilation are essential to having a well-functioning root cellar. If you lose more than thirty percent of your crop to spoilage each season, you will have to figure out which of these conditions are not being met.
The optimum temperature for your root cellar is between 32ºF and 40ºF Fahrenheit. This fairly cool temperature helps to slow the release of ethylene gas from certain vegetables and will also slow the growth of microorganisms that cause foods to decompose. If the temperature gets too warm, the food will rot or get moldy; too cool a temperature and the food will freeze, causing it to become soft and mushy after it thaws again. Extreme temperatures will cause the food in your root cellar to deteriorate faster, so it is important to make sure you insulate well and regulate the temperature.
The town of Elliston, Newfoundland, in Canada is the known as the “Root cellar capital of the world.” They have 135 documented root cellars in the area. The oldest surviving root cellars date as far back as 1839 and are still in good condition and used today.
The temperature in a root cellar is never uniform, and knowing which areas are colder or warmer will enable you to store your produce in the proper areas. You will need at least two thermometers to regulate the temperature inside your root cellar. Place one in the coldest part of the cellar, one on the outside of your structure, and closely monitor each area. Regulate the inside temperature by opening doors and windows, and opening or closing ventilation pipes.
The optimum relative humidity in a root cellar is between 85ºF and 95ºF percent, and every root cellar should have a hygrometer to properly regulate the humidity. Too much moisture and your food will rot and deteriorate more quickly; too little and your food will shrivel up, leaving nothing for you to eat.
A damp dirt floor will give you the best results for achieving the ideal humidity in your root cellar. A concrete floor will also work, but will tend to lower the humidity in the cellar and therefore needs more regulating to get the best results.
Here are some easy ways to add moisture to your root cellar:
Sprinkle the floor with water, especially a few days before you start bringing in the freshly harvested veggies.
Leave large pans of water near the intake air vents.
Cover the floors with wet materials such as damp straw or sawdust.
Shovel some snow into the root cellar to cool and humidify the area.
Pack vegetables in damp sawdust or peat moss.
Too much humidity can be just as damaging to the food stored in your root cellar as too little. Cold air does not hold as much moisture as warm air so moisture will collect on the roof or shelves and cause condensation if the cellar has too high a humidity content. Keeping the humidity regulated so there is no condensation is your best practice for preserving your food. If condensation does appear, make sure no water is dripping directly onto your vegetables or fruits.
Ventilation and Air Circulation
You will want to make sure your root cellar is equipped with one vent allowing air to flow in and another vent allowing air to be released. Keep in mind that it is easiest to put these vents in when building your root cellar. Ideally you will want the intake vent to be low and the outtake vent to be placed higher up; cool air will be able to enter the cellar, and as warm air rises it will be released through the outlet vent. A mesh cover placed over each vent will prevent rodents from getting in.
The vents allow both the temperature to adjust and the air in the root cellar to circulate freely. In extremely cold or extremely warm climates, you have the option of blocking the intake vent to prevent intense temperature from entering. Make sure you open it regularly to allow the air to circulate since this is a critical factor in minimizing any airborne mold. One way of maximizing airflow is to make sure your shelves sit a few inches away from the walls. Another is to store containers of foods and jars of preserves with some space between each.