Sweet potatoes are usually ready to harvest about 90–120 days after planting, when the vines start to yellow and you are within a week or two of your first expected frost.

Key signs they’re ready

  • Vines and leaves begin to turn yellow or look tired rather than lush and deep green.
  • You’re roughly 90–120 days from planting slips (some varieties may take up to about 140 days).
  • Weather is cooling and frost is getting close; harvest before the first frost or before soil drops below about 50°F.

Simple “dig-and-check” test

  • Pick one hill, dig carefully with a fork 12–18 inches away from the plant, and gently expose a few tubers.
  • If most roots are at least “store‑bought” size, go ahead and harvest the bed; if they’re very skinny and frost is still weeks away, you can wait a little longer.

How to harvest without damage

  • Cut the vines back a day or two before digging to make handling easier and help skins toughen slightly.
  • Use a garden fork or shovel to loosen the soil and lift the roots gently; avoid stabbing or dropping them because sweet potatoes bruise easily.
  • Brush off loose soil only; don’t wash them yet if you plan to cure and store them.

After harvest: curing for sweetness

  • Cure sweet potatoes in a warm, humid place (around the low 80s °F with good ventilation) for about 7–14 days to heal small nicks and develop richer sweetness.
  • After curing, store them in a cool, dry, dark place above 50°F; properly cured and stored roots can last through much of fall and winter.

Information gathered from public forums or data available on the internet and portrayed here.