The arrival of freezing temperatures is an integral part of this process; some vegetables must come out of the ground before any frost occurs, but others don’t complete their ripening until they’ve experienced a freeze. Frost occurs from between 36˚F to 32˚F; light freeze is 28˚F to 31˚F, moderate freeze is 24˚F to 28˚F, and a hard freeze is temperatures below 24˚F.
In temperate regions, some root vegetables can remain in the ground if heavily mulched. However, heavy rain or standing water can cause decay.
Which root vegetables must be harvested before a freeze?
Rutabaga, or Swede
Onions & shallots
Radishes (can withstand very light frost)
Which root vegetables improve with freezing temperatures?
Onions & ShallotsSome veggies can be left in the ground until freezing weather by mounding soil over the shoulders of vegetables like carrots and beets. This protects them from snap freezes. Straw is also an excellent insulator against frigid temps and can delay harvest a bit longer. Once the freeze comes, dig the remaining roots, clean them well, and store in a cool, dark, dry area.
Parsnips are an exception to the rule, as they withstand freezing and even improve in ﬂavor if left in the ground to dig in the spring.
Storing the harvest
Always select the best of the crop to store; and use, preserve, or freeze any that are not perfect. Check stored vegetables frequently and discard any that have deteriorated.
Home gardeners can utilize several different ways to mimic a root cellar, if one isn’t available. The key to root storage is controlled humidity, moderately cool temperatures, and no light depending on the variety. A good storage area must also be protected from ground water and rodents.
The University of Minnesota Extension Ofﬁce outlines three combinations for long term storage: 1) cool & dry: 50-60˚F and 60% relative humidity; 2) cold and dry: 32-40˚F and 65% relative humidity; and 3) cold and moist: 32-40˚F and 95% relative humidity.
Some simple storage solutions include an outdoor pit such as a barrel buried halfway into the ground at an angle. If the pit is lined, this will protect the produce from water and rodents. Loosely cover the barrel-not airtight-then cover with a deep layer of straw (1 to 3 feet) followed by a layer of soil. Place a board against the side of the pit where the opening of the barrel faces.
A storage mound is used where water is a problem, or short-term storage in mild temperatures. Place a layer of straw about 3 inches thick on the ground, then place the vegetables on the straw. Cover the mound of vegetables with a thick layer of straw followed by a layer of soil. Dig a drainage trench around the mound.
There are several plans for incorporating a root cellar into an existing basement, but the main idea is to provide an insulated area where temperatures can be kept between 33 and 45 degrees. An Internet search on “root cellars” will provide many ideas and instructions.
Enjoying rich, ﬂavorful rutabagas and parsnips, or creamy home-grown potatoes in the dead of winter is one of the delights of being a gardener. Plan to include some of these root vegetables in your next season.
Other Excellent Sources of Information
Images from Wikimedia Commons, by GNU License or in public domain; carrots by Toni Leland