Temperature & Humidity
Different produce items have different skin types, so the optimal temperatures and humidity levels for maximum storage life will vary. Controlling the temperature and humidity in the cellar and keeping tabs with thermometers and hygrometers optimizes produce life.
Vegetables such as beets, Brussels sprouts, cabbage, carrots, parsnips, and turnips all do best in low temperature (33° to 40°F) and very high (90 to 95 percent) relative humidity. Some are better in the same low temperature but with high (80 to 85 percent) humidity. These include apples, citrus fruits, leeks, pears, potatoes, and quinces. Others, such as onions and garlic, are better in relatively higher (40°F to 50°F) temperature and lower (60 to 70 percent) humidity. The temperature in a cellar will vary, with cooler temperature near the floor and warmer at the ceiling, but that variance may not be enough. Explore different venting and cooling techniques to make the cellar temperature fit your needs. Keeping it more humid is usually trickier than keeping drier conditions. For simplicity, store produce items that favor similar conditions when you're starting out.
Exploring Storage Containers
Appropriate storage containers can also go a long way toward preserving produce. Wooden crates are simple and good for many types of produce when the cellar is at the correct humidity. Portable ones allow you to rearrange the cellar easily, while permanent ones can be built into the cellar for large amounts of a single food.
"Sand buckets" can be created from any bucket, can, or sealed wooden box. As you layer beets, carrots, or other root crops, fill the container with sand. This method makes it easy to keep the humidity level high for roots, since you can sprinkle water on the sand without increasing the overall humidity in the cellar.
Open racks work well for squash and cabbage that are bulky and awkward to pack in crates. While some varieties of produce won't affect others and can be stored side-by-side, that doesn't apply to everything. Apples, for example, release ethylene gas, which can cause potatoes to sprout; therefore they shouldn't be stored close to each other. The flavor of onions can transfer to more mild foods.
Begin with the best keepers, and as you get to know the ins and outs of the cellar and the science of storage, branch out into more delicate foods that need specialized care. Good starter foods include apples, beets, cabbages, carrots, ginger, onions, parsnips, potatoes, and pumpkins. Master cellaring and you'll enjoy the fruits (and vegetables) of your harvest until the next season rolls around.
Try these quick and easy recipe is adapted from The Complete Root Cellar Book, by Steve Maxwell and Jennifer MacKenzie (Robert Rose Inc., 2010; www.robertrose.ca). Reprinted with permission.
5 Steps to Good Storing
Only the best.
Damaged produce doesn't store well. Use broken or bruised roots right away, and store only perfect produce in your cellar.
Keep it dirty.
Store produce as close to its state at harvest as possible (clinging soil, roots and stems intact). Gently rub off big clumps of dirt, but avoid scrubbing or washing. Remove the leaves of roots such as beets and carrots.
Sort it out.
Sort produce by size and quality before storage; use the smallest and any slightly marked produce first and work to the largest as you use up your stores.
Frost is your friend (sometimes).
Vegetables such as beets, Brussels sprouts, cabbage, turnips, rutabagas, pumpkins, and horseradish benefit from a touch of frost before harvesting for better storage and flavor.
Shock it first.
Harvested onions continue to grow unless they're shocked into dormancy. About 1 month before harvest, break each green stalk by snapping or bending to stop the root (the onion) from feeding the plant. Shocked onions in a cool, dry cellar will keep for 4 to 6 months.