Michigan State University Extension
Preserving Food Safely - 01600025
Root crops may be stored in the garden or the root cellar. If left in the garden, they should be covered with 1 1/2 - 2 inches of insulating material. Parsnips, salsify and horseradish are particularly sensitive to alternate freezing and thawing so keep them covered until outside temperatures are consistently low, then remove the mulch to permit thorough freezing. After they have frozen, mulch them deep enough to keep them frozen.
Before storing root crops in the cellar, wait until the storage area is cool. The plants may be left in the garden until then (late fall). Dig up the root when the soil is dry so less soil will cling to the roots. Cut off the root crop tops about 1/2 inch above the root. They may be washed, but should be allowed to dry before being stored. Temperature of the storage area should be between 32 and 40 degrees Fahrenheit and very humid. Temperatures above 45 degrees Fahrenheit will encourage woodiness and sprouting. Pack the root crops in bins or crates between layers of moist sand, sawdust, sphagnum or peat moss. Containers should be lined with a perforated plastic sheet.
If the humidity is not high enough in the storage area, place the roots in plastic bags in which at least 4, 1/4 inch holes have been cut. Store only healthy root crops. If storage conditions are right, the root crops should keep 3 to 5 months, except for kohlrabi, which keeps for only a few weeks.