Root cellars were used extensively by our ancestors to preserve food.
The combination of cool temperatures and a moist environment is the equivalent
of storing in a refrigerator. As we move toward keeping our produce at a
lower cost, a root cellar may be in your future.
I'm Linda Tannehill from the University of Alaska Fairbanks Cooperative Extension Service.
So what is a root cellar?
They come in many different forms, in both indoor and outdoor types.
An outdoor storage can be as simple as a buried box or a container all the way to a
separate freestanding structure. An indoor structure can be an unheated
section of the basement, under the floor,
or in the garage.
Building a root cellar is highly dependent on the site. Controlling temperature, humidity, and
ventilation is crucial, so carefully select the site and type of structure.
At the end of this lesson, I'll give some general guidelines for root cellars.
If you're considering building a root cellar, consult your local
Cooperative Extension Service agent for more information.
In areas of Alaska where permafrost is not an issue, above-freezing subsoil temperatures make
root cellaring a good alternative for storing fruits and vegetables.
Root cellars may be of interest to gardeners growing excess produce and consumers
purchasing quantities of in-season produce, both wishing to extend the
quality and storage duration of their produce.
Fruits and vegetables held in cold storage are living organisms whose maturation processes are slowed
by the manipulated environment. Each crop stored has specific temperature, humidity,
and ventilation requirements necessary to maintain optimum long-term nutrition and quality.
Conditions in the root cellar depend on three main factors:
temperature, humidity, and ventilation.
Products suited to root cellar storage can be grouped according
to the temperature and humidity requirements for each.
For best results, store fruits and vegetables separately.
During storage, it is important to slow down the growth and respiration of
produce through the exposure of temperatures slightly above freezing.
The optimum storage temperature for most produce is dependent on plant type or species.
Cool temperatures may be maintained naturally by opening up the
floor to bare earth, while insulating walls and ceilings to keep colder temperatures out.
In permafrost areas and in situations where root cellars are not
buried deep enough, a thermostatically controlled heat source
may be required to keep internal temperatures above freezing.
Controlling humidity is very important, but often difficult to achieve.
Humidity is manipulated to keep vegetables from drying out or rotting.
A small, full cellar will increase humidity as vegetables respire,
giving off carbon dioxide and water vapor.
A root cellar with an earthen floor, such as sand, soil,
or gravel, will have a higher humidity level than one with cement or wood floor.
In some cases, packing vegetables in damp sand or sawdust may help maintain
required high humidity levels around vegetables.
Moisture is very important to storage of vegetables. All produce should be stored in a moist environment.
Even the lowest recommended humidity range for vegetables is 60 percent.
Ventilation helps to maintain adequate oxygen levels and control temperatures and humidity.
Crowded conditions in a closed-up root cellar can create oxygen deprivation and
moisture problems. Be sure to screen the ventilation system to keep rodents out.
Depending on the crop, harvest as late in the season as possible
and before a killing frost damages the produce in a garden.
Attempt to harvest in the morning after the dew has dried
but before vegetables have been warmed by the sun.
If warmed, cool vegetables before storage.
Supplies needed for the root cellar are simple. You'll need bins, baskets, food-grade buckets or containers
to store produce, packing materials such as sand, sawdust, or peat moss,
and newspapers.
Some vegetables need cold and very moist storage conditions because of
thin skin or leaves. These include beets, carrots, cucumbers,
kohlrabi, parsnips, radishes, and turnips. Leave 1/2 inch stem, if possible, to
retain moisture. Layer vegetables and packing material such as perforated plastic,
moist sawdust, moist sand, or peat moss. If using sawdust, use only hardwoods
or very old conifer sawdust as spruce contains volatile chemicals that can
impart a flavor and odor to vegetables stored in them.
Vegetables with strong odors, such as this cabbage or turnip
store best when individually wrapped in newspaper to reduce smells and prevent drying.
Many fruits can be preserved by canning, freezing, and drying.
Only fruit that mature in the late fall or that can be purchased in the winter should be
considered for home storage. Apples and pears require a cooler temperature than
most vegetables. And air circulation is required to remove gas produced by the fruit.
This gas speeds up the ripening process if not removed.
The optimum temperature for apples is 30 to 32 degrees Fahrenheit
with a 90 percent relative humidity.
Pears require 29 to 31 degrees Fahrenheit with a 90 percent humidity.
Apples and pears will keep longer and retain more flavor
if individually wrapped in tissue or newspaper
and placed in boxes lined with perforated plastic.
Carrots are a great Alaska product that need cool and very moist conditions for storage.
I'll use a sand pack. Start with a bed of damp sand. Place a layer of carrots on the damp sand.
Don't allow the carrots to touch.
Sprinkle damp sand over the top of the carrots, about an inch thick.
This prevents the carrots from drying out.
Add another layer of carrots and continue the process until the container is full
or you run out of carrots.
Potatoes and tomatoes store best in cold, high-moisture conditions of 32 to 40 degrees
Fahrenheit and 80 to 90 percent relative humidity.
If you just dig the potatoes and put them into the root cellar,
you'll have problems.
It's important to put the potatoes in a warm and dark environment that will allow
them to dry and the skins to toughen, which is in an area that is
approximately 55 degrees Fahrenheit for 21 days.
Once they're dried and toughened, they're ready to be placed in the bin and stored in the root cellar.
For long-term storage, move potatoes to a dark area not above 40 degrees Fahrenheit.
Harvest tomatoes leaving a short stem attached.
Place tomatoes one layer deep and cover them with newspaper
to keep them from drying out.
Onions store best in cool, slightly moist conditions. This is approximately 32 to 50 degrees Fahrenheit
and 60 to 70 percent relative humidity.
Onions need to be cured for several weeks after harvest
to allow the skin to become papery and to dry the roots.
Warm, slightly moist conditions work best for winter squash and pumpkins,
50 to 55 degrees Fahrenheit and 60 to 75 percent relative humidity.
Harvest these vegetables as late as possible and, if possible, leaving a 2-inch stem.
The more mature the squash, the thicker the skin, and more resistant to decay and drying out.
A root cellar should, above all, be structurally sound.
It also needs to be kept cold, dark, damp, and in a convenient location.
One possible location may be a walled off section of a basement or garage
or, like this one, under the garage.
With an inside installation, be sure to put a vapor barrier towards the inside
of the root cellar to protect the house from excess moisture and rot.
In both attached and separate structures, the use of treated wood is not recommended.
Uninsulated masonry walls and ceilings will allow cold temperatures to permeate
if left uninsulated.
Insulate ceilings and walls down below the frost line to
protect the interior from excessively cold temperatures.
In some areas, seasonal frost can penetrate more than 4 feet below the soil surface.
A small room will work for storage of vegetables requiring the same temperature and humidity.
The use of moist sand and sawdust will allow the storage of some vegetables with
different humidity requirements. While considered a luxury, a multi-room cellar
works best for storing produce with multiple requirements.
If you're considering storing your vegetables in a crawl space,
check the temperature. Be certain your proposed storage area maintains the
proper storage condition throughout the year.
Remember, the key to successful root cellaring is begin with high-quality, fresh produce.
The key to a successful root cellar is controlling temperature, humidity, and ventilation.
For further information, contact the Cooperative Extension Service
for a publication on storing fruits and vegetables in a root cellar.