Cold storage of root crops, cole crops, winter squash, onions and garlic

Congratulations on a fine crop of vegetables! Some to eat, some to share and some to store into the fall and winter. If you don't plan on canning or freezing your harvest, cold storage can keep your produce fresh and fit to eat long after harvest. Cold storage keeps your produce dormant, so that it does not over-ripen or rot. Every vegetable and fruit will stay fresh at the right temperature and moisture level, from cold and damp, to warm and dry.

Preparing produce for cold storage
Harvest your produce at peak maturity. Store only the best produce: avoid storing anything that is diseased, has severe insect damage or has been cut, damaged or bruised. Like any living thing, cuts are sites for infection like mold or rot. Preparing vegetables correctly before storing will extend storage life.

Root vegetables
Leave about 2 cm (1 inch) of stem on root vegetables like carrots, parsnips and beets. This will prevent shriveling. Gently brush off excess soil. Place vegetables in a single layer on cardboard or newspaper. Set them in a cool dry and dark place to cure or dry for a day or two. Brush off any remaining excess soil and get ready to store.
 
Washing is not necessary, in fact it’s better not to wash. Washing can damage the outer skin of the vegetable which can lead to rot. Some like to wash root vegetables with cold water to remove the soil. If you do this, make sure that the vegetables are completely dry before you store them to avoid rot. They still need to be cured for a day or two before storing.

Onions and garlic
Onions and garlic need to be cured (dried) before storing. Trim off the tops to 3 – 4 cm (1 ½ - 2 inches). Set garlic and onions on a layer of newspaper or cardboard in a warm, dry, dark place. Leave onions for about a week and garlic for 3 – 4 weeks. Check regularly to see if any onions or garlic are mouldy and remove them right away. Once they are dry, remove the roots (which should be dry) and any loose outer papery skin.

Winter squash
Winter squash includes pumpkin, butternut, spaghetti and acorn squash. When harvesting squashes, leave a 5 – 7 cm (3 inch) stem. The stem also prevents the squash from drying out. Squashes need a short period of curing.  Curing is simply drying the squashes so that they develop a tough outer skin that prevents them from drying out. Set the squash in a dry, dark place at room temperature for about a week before moving them into cooler storage.
 
For more information about harvesting your vegetables when they are at their best see: Harvesting vegetables

Good storage places for vegetables
Most vegetables need cool temperatures for long term storage, while other vegetables like onions and winter squash need a bit more warmth. Check the Vegetable Storage chart below for ideal temperature ranges for storing your vegetables.

Even if your storage temperatures are not ideal, you can still get a long shelf life out of your vegetables in cool conditions. Before you store, measure the temperature in your storage areas with a thermometer. Since cold air is heavier than warm air, you might find that the floor is colder than a shelf that is higher up. This will help you decide where to put which vegetables. It’s important that any area you choose does not freeze. The ideal temperature is even and should not fluctuate too much. Freezing can damage your vegetables while too much warmth can make them sprout or over-ripen.

Root cellars
Some homes have a root cellar in the basement, which is an unheated room that stays cool but does not freeze. Some root cellars are dug into the earth and accessed by a hatch or door. All root cellars need insulation to keep from freezing; and ventilation for air circulation and temperature control.
Here are some basic plans and alternative ways to make a root cellar: Cold storage options

Other places in your home to store vegetables
Many homes have other spots that are cool in winter. It could be the attic, a mud room or arctic entrance, a crawl space, an unheated room, a cool spot in the basement, a closet, cupboard or even under the stairs. A heated workshop or outbuilding that is cool can work too. The area should stay evenly cool without freezing or warming.
 
Some vegetables, like garlic and winter squash need to be stored at warmer temperatures. Choose a place like a cupboard, closet or shelf in the kitchen or bedroom for these vegetables.

Refrigerator
There may not be enough room in your fridge to store all of your extra harvest. However, if you have a second fridge, you can store a lot. A fridge is a good place for cold, damp storage. You can set the temperature in most fridges. Crisper drawers hold more moisture and are good places to store root vegetables. Otherwise, use perforated plastic bags to keep root vegetables moist.

Temperature and humidity
Besides temperature, relative humidity is important too. Humidity is the amount of water vapour air can hold depending on the temperature. Relative humidity can be measured using a hygrometer. You don't need to buy a hygrometer if you store vegetables correctly.

Cold and damp
Beets, carrots, parsnips, horseradish, turnip, rutabaga, Jerusalem artichoke, cabbage, Brussels sprouts, cauliflower and kohlrabi need to be kept cold and damp. The temperature should be just above 0ºC / 32ºF to a maximum of 5ºC / 40ºF. These vegetables need high humidity. Use perforated bags or bins packed with moist packing material to store these vegetables. See below: How to get the moisture level just right.

Cool and slightly damp
Potatoes should be stored cool and not too dry. The ideal temperature range is 3ºC – 5ºC (38ºF – 40ºF). Unlike other root vegetables which need damp storage, potatoes can be stored in perforated plastic bags as long as the potatoes are not damp. The bags help to prevent the potatoes from shriveling. Check your potatoes often as too much moisture will cause them to rot. You can also use large, shallow bins or boxes to store potatoes.

Warm and slightly damp
Winter squashes like pumpkin, acorn, butternut and spaghetti squash need warmer temperatures but air that is not too dry. Do not store in plastic as this can cause rot. Store on a shelf and do not let the squashes touch one another.

Cool and dry
Onions and garlic need to be cured before storing. They will last longer if they are not piled up too much and have good air circulation. Use mesh bags, baskets or any box (plastic or cardboard) with slats or holes to allow air circulation.

How to get the moisture level just right

Perforated plastic bags for damp storage
Plastic bags are a way to keep produce like root vegetables moist but not too wet. Perforated bags have holes that allow excess moisture to escape. Use clips or twist ties to seal the end of the bags. Too much moisture causes produce to rot while too little causes produce to wilt or shrivel. If you notice wilting, use a spray mister to add moisture. If there are soft spots or rot, remove the spoiled vegetables.
 
Never use black garbage bags or grocery bags to store vegetables for long periods of time. These plastics may contain chemicals that are bad for you if the bag comes into contact with food.
 
A good choice is clear plastic that is made for food storage. Make your own perforated bags by punching holes in the bags using a knife or scissors. You can recycle plastic food bags that have been used to store bread or vegetables. Wash with warm soapy water, rinse and air dry before using. Never use food bags that were used to store meat or fish as they may be contaminated by bacteria that can make you sick.

The pail or bin method for damp storage
Root vegetables like beets, carrots, parsnips, horseradish, turnip, rutabaga and Jerusalem artichoke need cold and damp storage. They can be stored for long periods in clean, large pails, plastic bins, Styrofoam coolers or wooden crates. Pack sphagnum moss, peat, sawdust or sand that is slightly damp around the vegetables to keep them from drying out. Do not allow water to pool at the bottom of the container.
 
Start by putting a 3 cm layer of damp sphagnum moss, peat moss, sawdust or sand at the bottom of the pail or bin. Put in a layer of the vegetables, and cover with a layer of the packing material. Repeat until the container is full and top with a final layer of packing material. Cover with a lid and store in a place that is cool – just above freezing.

Containers with air circulation for dry storage
Select containers that allow air to circulate around onions and garlic which need to stay dry. Even a small amount of moisture can encourage molds or rot. Mesh bags, wicker baskets or any box (plastic or cardboard) with slats or holes are good choices.

Vegetable storage chart

Adapted from: Food storage guide Cornell University

Troubleshooting 

Use your vegetables!
Cold storage will keep vegetables fresh for a long time, but they won't last forever. Use your vegetables every week.
 
Sources:

Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010) Putting Food By: Fifth Edition. New York, New York: Penguin Publishing Group (USA) Inc.

National Centre for Home Food Preservation

https://rvpadmin.cce.cornell.edu/uploads/doc_500.pdf

https://nchfp.uga.edu/how/store/wisc_vegetables.pdf

https://cdn.shopify.com/s/files/1/0145/8808/4272/files/A3823.pdf