The harvest period for most vegetables ends with the first hard frost. However, the quality of some root crops, such as parsnips, salsify, and horseradish, improves with exposure to cool fall temperatures. Delay harvesting the aforementioned root crops until mid- to late November in Iowa.
Parsnips produce white to cream-colored roots which have a sweet, nut-like flavor. Cool temperatures convert starch to sugar and give parsnips their distinctive flavor.
When harvesting, dig parsnips carefully as damaged or broken roots do not store well. After harvest, trim the foliage back to within 1 inch of the roots. Store parsnips at a temperature of 32 degrees Fahrenheit and a relative humidity of 95 to 98 percent. Small quantities can be placed in perforated plastic bags and stored in a refrigerator. A basement storage room or root cellar are suitable storage sites for large quantities.
Gardeners can also leave a portion of the crop in the ground over winter. In late November, cover the parsnips with several inches of straw. Harvest the remaining crop in early spring before growth resumes.
Harvest salsify in mid- to late November as cool fall temperatures enhance the oyster-like flavor of the roots. After harvest, trim off the foliage 1 inch above the roots and store the salsify at a temperature of 32 degrees Fahrenheit and a relative humidity of 95 to 98 percent.
Salsify can also be left in the garden over winter. In late November, cover the salsify with several inches of straw. Harvest the remaining salsify 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, harvest horseradish in late 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 degrees Fahrenheit and a relative humidity of 90 to 95 percent. When storing horseradish, keep the roots out of light. Light turns the roots green.
Horseradish can also be left in the ground over winter. Harvest the remaining crop in early spring before growth begins.