Check the plant tops: when they yellow, start to die back, and dry out, potatoes are usually nearing harvest
For new potatoes, harvest when plants are still green but have flowered
For mature potatoes, wait until the foliage has completely died back
Gently dig around one plant to see if tubers are a usable size
Harvest when the skin is set and does not rub off easily when rubbed with your finger
If the variety is a maincrop type, wait about 2–3 weeks after the tops die back before harvesting
Avoid harvesting if the soil is very wet
Harvest before a hard frost if possible
Check for signs of overmaturity such as cracked skins or sprouting
Use the expected days-to-maturity for the variety as a timing guide