Root crops are popular in home gardens because they are easy to grow and produce an abundance of nutritious food in a small space. Iowa State University Extension horticulturists tell when to harvest parsnips, salsify and horseradish – roots that some consider to be winter vegetables because their flavor is not fully developed until the roots have been exposed to near-freezing temperatures. To have additional garden questions answered, contact the ISU Extension Hortline at 515-294-3108 or firstname.lastname@example.org.
Parsnips should be harvested in November after exposure to several light freezes. The low temperatures in fall convert starches to sugars, improving the parsnip’s sweet, nut-like flavor. After harvest, trim off the foliage 1/2 inch above the roots and store the parsnips at a temperature of 32 degrees Fahrenheit and relative humidity of 95 to 98 percent.
Gardeners can also leave a portion of the crop in the ground over winter. After several light freezes, cover the parsnips with several inches of straw. Harvest the remaining crop in early spring before growth resumes.
Harvest salsify in November after several light freezes. The cool fall temperatures enhance the oyster-like flavor of the roots. After harvest, trim off the foliage 1/2 inch above the roots and store the salsify at a temperature of 32 F and a relative humidity of 95 to 98 percent.
Salsify can also be left in the garden over winter and harvested in early spring before growth resumes.
The roots of horseradish make their greatest growth in late summer and early fall. To obtain the best crop, delay harvesting horseradish until late October or November.
Carefully dig the horseradish and cut off the foliage about 1 inch above the crown. Store horseradish in a refrigerator or root cellar at a temperature of 32 to 40 F and a relative humidity of 90 to 95 percent. When storing horseradish, keep the roots out of light. Light will turn the roots green.
Gardeners can also leave some horseradish in the ground over winter. Harvest the remaining crop in early spring before growth resumes.
The asparagus foliage can be cut back to the ground after it has been destroyed by a hard freeze in fall. However, it is generally recommended that the dead foliage be allowed to stand over winter. The dead debris will catch and hold snow. Snow cover helps protect the asparagus crowns from extreme cold. Asparagus foliage allowed to remain in the garden over winter should be removed in late March or early April before the spears begin to emerge.