Sweet potatoes don't ripen the way a tomato does. The roots keep getting bigger as long as the vines are growing in warm soil, so harvest is a judgment call. Most varieties are ready 90 to 120 days after the slips go in. Around day 90, dig carefully at the edge of one plant and look. When about a third of the roots are larger than 3½ inches across, the cr is ready. Cracks in the soil around the crown can be another sign that the roots are swelling.
The cutoff is cold, not the calendar. Dig before soil temperatures drop below about 60°F, because chilled roots lose quality and store poorly. In practice, that means digging before your first fall frost or immediately after a frost kills the vines. Don't leave roots in the ground for days under blackened vines. Cold, wet soil and dead tops can let rot start.
Dig carefully. The skin of a fresh sweet potato scuffs and bruises at the slightest knock, and every wound shortens storage life. Cut the vines away first. Then put a fork or shovel into the soil well out from the crown and lift each hill whole. Dig when the soil is slightly moist rather than bone dry, which causes more skinning. Don't wash the roots, and move them out of the sun.
Curing is what turns a starchy root into a sweet one. It heals scrapes and converts some starch to sugar. The ideal is about 80 to 85°F with 85 to 95 percent humidity for 7 to 10 days. Few homes have a spot like that, so put them in the warmest room you have, often the kitchen, for about two weeks. Little curing happens below 70°F. Skipping this step leaves roots that taste bland and spoil sooner.
After curing, store sweet potatoes somewhere dark at 55 to 60°F. Never refrigerate them. Below 55°F they develop hard cores and off-flavors, and above 60°F they tend to sprout. A cool closet or basement corner often works. Well-cured roots can keep 4 to 6 months or more. Check them now and then and use any that show soft spots first.
- Meadow VolePlants collapse with roots eaten; shallow surface runways and gnaw marks at stem bases near soil.
- WirewormTunneled seeds, failing seedlings, and holed root vegetables — caused by firm yellowish larvae living in soil for multiple years.
- Cabbage MaggotBrassica transplants wilting and dying as white maggots tunnel through roots at or below the soil line.
- Onion MaggotOnion seedlings and sets collapsing at the base, with white maggots tunneling into bulbs at or below the soil line.
- Root-Knot NematodeStunted, wilting plants with characteristic knobby galls on the roots. Worst in sandy soil and warm climates.
- How do I store winter squash so it lasts through winter?Cure winter squash at 80–85°F for 10–14 days to harden the skin, then store at 50–60°F in a cool, dry location — not the refrigerator.
- How can I extend my growing season in fall?Row cover fabric, cold frames, and switching to cold-hardy crops are the three most reliable tools for extending production 4–6 weeks past your first fall frost.