Winter Storage of Fruits and Vegetables
For many of us, the vegetable harvest season has wrapped up. Shelf-life, or how long a fruit or vegetable remains in edible condition following harvest, is partially determined by factors while growing in the field, such as disease, temperature, and fertilizer rates. After harvest, the challenge becomes creating the perfect conditions to keep that crop in good condition. Variety, temperature, humidity, ventilation, quality, and light all play a role in determining how long a fruit or vegetable will last. Some can be stored indoors, while others can be outdoors in protected sites. For those growing large gardens and storing many crops, you may consider creating separate storage areas for each. Potatoes, sweet potatoes, onions, winter squash, and garlic are commonly stored items, but many more can be stored without refrigeration given proper conditions.
One of the most important factors in determining shelf-life is produce quality. Damaged fruits and vegetables will not last as long, and should not be placed in long-term storage as they could reduce shelf-life of the other stored crops. Post-harvest handling practices also affect how long a vegetable or fruit will stay fresh. Many crops need to be cooled quickly once harvested from the garden or field, in order to maximize shelf-life. Sweet potatoes and winter squash require 2-week curing periods of 85-95 degrees F following harvest. Then, they should be stored at 55-60 degrees F, with the exception of Acorn squash, which does better at 45-50 degrees. However, sweet potatoes prefer a humid curing and storage environment (90-95% relative humidity), whereas pumpkins and squash do better in low humidity (65-70%). Many homes during winter are too dry for even pumpkins, so if you are storing these in your living areas, you may observe some shriveling due to dehydration over the winter. Do not store them in the refrigerator, unless you are storing them after having cut the vegetable.
Irish potatoes- our “typical” potatoes- store best between 45 and 50 degrees F and higher humidity, with slightly lower temperatures required to prevent sprouting. Other important considerations for potato storage are light and temperature fluctuation. Temperature fluctuations can initiate sprouting, and light exposure can cause green spots to form. Green spots and sprouts should be removed before eating as they have higher solanine content, which is toxic to humans when consumed in high doses.
It is simple enough to construct indoor storage areas for specific crops. Avoid building them close to windows or doors as these areas will fluctuate in temperature. Build them in a way that is easy to check periodically, and plan to inspect them regularly and remove any decaying or rotten items. Store varieties with the shortest shelf-life in the most accessible spot, and place longer lasting crops in areas that become more accessible through the winter as things get consumed. Basements and crawl spaces often make good storage areas as temperatures remain steady, and humidity is often higher. You can also maintain higher humidity levels indoors by placing pails of water under storage shelving or by storing roots in polyethylene bags or box liners with ventilation holes. Drier indoor spaces are suitable for storing dried herbs and conserved goods.
Outdoor storage areas can be as simple as a mound built on top of the soil, or a container buried in a pit. In the mound system, a layer of straw mulch is placed on the soil surface, followed by the stored crops. The crops are then covered with a layer of mulch or insulating material, and then the whole mound is covered with soil. Different containers can be used for burying crops in the ground. The container should not have any chemical residues and should have drainage holes installed to release any moisture. Both mounds and buried containers need a straw-filled air vent. Place a layer of mulch between fruits and vegetables, at least, or separate each crop with a layer of mulch.
Fall-planted beets, carrots, turnips, and parsnips are good candidates for storing in the garden. Yes, in the garden! These hardy roots tolerate some frost and can be stored in the garden bed where they were grown, and harvested as needed through the winter. The light frost events help convert starches in the root to sugar, leaving a sweeter root to enjoy. Since hard freezes can damage the roots, apply approximately one foot of straw mulch or dried leaves over top of the roots once freezes are predicted. Use a tall sign to mark each bed, so you can find the plants through the mulch and in the event of snow when you want to harvest.
A few other practices are important for maximizing storage shelf-life. Plan to sanitize storage containers and areas yearly to reduce decay from molds or disease. Make a plan for preventing rodents or controlling them should they become an issue. Never store apples with potatoes or carrots as they produce ethylene, and will cause bitterness and sprouting. Potatoes can lend a musty flavor to apples when stored together. Cabbages, rutabaga, turnips, and other members of the cabbage family should be kept in an outdoor storage area as they can produce strong odors that are not desirable in a home. More detailed information on storing vegetables and plans for building your own storage areas.
With questions on winter gardening or food storage, contact the N.C. Cooperative Extension, Caldwell County Center at 828-757-1290, Monday-Friday, 8 a.m.–5 p.m.