When to Harvest Potatoes

Two harvests from one planting

Potatoes give you two choices. You can take some early as new potatoes and leave the rest to mature, or you can wait for the whole crop. The timing depends on what you plan to do with them. New potatoes are for eating right away. Mature potatoes with set skins are the ones that keep.

New potatoes: 7 to 8 weeks, around flowering

NC State puts the first new potatoes about 7 to 8 weeks after planting, once the plants begin to flower. UGA also uses first flowers as the signal.

To harvest without losing the plant, work your fingers or a trowel into the side of the hill. Pull a few of the largest tubers near the surface, then firm the soil back over the rest (Utah State, Texas A&M, UGA). New potatoes have thin, delicate skins that scuff easily and dry out quickly, so eat them within a few days rather than storing them.

Storage potatoes: vines down, skins set

The main crop is ready when the vines yellow and die and the skins have set. Clemson recommends digging storage potatoes about two weeks after the vines die down. Days from planting vary by variety and source:

• Texas A&M: 95 to 110 days
• Clemson: 100 to 120 days
• UF/IFAS: 85 to 110 days
• University of Arizona (low desert): 90 to 120 days

Use the skin test to decide. Rub a tuber firmly with your thumb. If the skin scrapes or peels, wait. If it holds, the potatoes are ready for storage.

If the tops are still green when you want to dig, cut them back. Texas A&M notes that removing the tops speeds skin set. Maine advises pulling or cutting the vines at least 7 days before harvest.

Texas A&M suggests aiming for most tubers to weigh 6 to 12 ounces at harvest.

Digging without damage

• Pick the right soil moisture. Texas A&M recommends digging when soil is moist, not wet or dry. Wet soil sticks to the tubers, and dry clods bruise them.
• Start well out from the plant. Push the fork in 8 to 10 inches from the stem (Texas A&M) and lift from below so you don’t spear tubers.
• Handle them like eggs. Maine’s advice is apt because potatoes bruise. Damaged potatoes don’t store well (Texas A&M), so keep only intact, healthy tubers for long-term storage and eat the rest first.
• Limit light. Clemson leaves tubers in the sun only an hour or two, just long enough for the soil to dry. UGA lets them dry on the ground for several hours. Either way, get them out of the light before they start to green.
• Don’t wash. Brush off dry soil and store them dirty (Utah State, UGA).

Cut back on watering when the vines begin to yellow. Wet soil late in the season is a major cause of storage rot.

Curing

Curing heals small wounds and thickens the skin before long storage. Utah State recommends 2 to 3 weeks at 55 to 60°F with high humidity, in the dark.

Storage

Once cured, potatoes keep best cold, humid and dark, though the recommended temperatures differ:

• Maine: about 38°F and 95 percent humidity
• Utah State: 40 to 45°F, with good air circulation
• Clemson: 40 to 50°F and about 90 percent humidity, for six to eight months

Warmer storage causes sprouting (Clemson). NC State’s figure for a simply cool, dry, dark spot is three to four months. Keep potatoes away from apples and pears, because Utah State notes that the ethylene from the fruit makes tubers sprout.

Late-season varieties keep longest (Clemson). Texas A&M notes that most red varieties store longer than whites.

Green potatoes

Any tuber exposed to light, in the garden or in storage, turns green. The green parts and any sprouts contain solanine, which is bitter and toxic. Cut away small green patches before cooking and throw out potatoes that are green throughout.