The success of a potato harvest hinges almost entirely on accurate timing, which is determined by the intended use for the tubers. Potatoes can be harvested for two distinct purposes: as “new potatoes” for immediate consumption, or as mature tubers destined for long-term storage. The difference in harvest readiness is stark, with new potatoes taken while the plant is still vigorous and mature tubers only after the plant has completely finished its growing cycle. Harvesting at the wrong time for the desired outcome can result in either small, delicate potatoes or large, thin-skinned ones that will not last in storage.
Timing the Harvest for New Potatoes
New potatoes are prized for their delicate flavor and thin, tender skin. The harvest window for these smaller potatoes generally opens about two to three weeks after the plant begins to flower, while the foliage is still green and healthy. At this stage, the tubers have not yet developed the thick, protective skin necessary for extended storage.
The best way to check for readiness is through “scouting,” which involves gently digging at the side of a potato hill to check the size of the tubers. Once you find potatoes about the size of a golf ball or a small hen’s egg, they are ready to be carefully removed. Removing some new potatoes early will reduce the overall yield of mature storage potatoes later in the season, but the remaining tubers can continue growing by carefully covering the exposed area with soil again.
Visual Cues for Mature Potato Readiness
The signal for harvesting potatoes intended for long-term storage is the complete dieback of the above-ground foliage, known as the haulms. The plant naturally begins to yellow and wither as it shifts its energy entirely into maturing the tubers underground, typically 90 to 120 days after planting, depending on the variety.
After the foliage has turned completely yellow and withered to the ground, it is necessary to wait an additional two to three weeks before digging. This waiting period is known as the “skin-setting” phase, which thickens and toughens the potato’s skin. A thick skin provides a protective barrier against moisture loss and physical damage, which is essential for preventing rot and extending the potato’s shelf life in storage.
Harvesting too early, when the skin is still thin, causes it to “feather” or rub off easily when handled, creating entry points for pathogens and leading to rapid spoilage. To confirm readiness, gently rub the skin of an exposed tuber with your thumb; if the skin resists peeling, the potatoes are ready. Delaying the harvest much past this two-to-three-week window can also be risky, as overly saturated or warm soil conditions may cause the tubers to rot or sprout prematurely.
The Steps for Digging and Curing
Harvesting mature potatoes requires caution to prevent bruising or puncturing the tubers, which compromises their storage potential. A garden fork is preferable to a spade because its tines are less likely to slice through a potato hidden just below the surface. Begin by inserting the fork several inches outside the perimeter of where the foliage was growing to avoid impaling the tubers.
Once the fork is in the ground, gently lift the entire cluster of soil and potatoes to loosen them from the earth. After removal, handle them as little as possible to avoid unnecessary nicks or scrapes. Brush off any large clumps of dirt, but resist the urge to wash the potatoes, as introducing moisture will drastically shorten their storage life.
The potatoes must undergo a curing process to heal any minor surface wounds and further strengthen the skin. Curing involves storing the potatoes in a dark, cool, and humid environment, ideally between 50°F and 60°F with high humidity, for a period of 10 to 14 days. This controlled environment promotes a natural healing response in the tuber, allowing a new layer of skin, called the periderm, to form over damaged areas. After curing, the potatoes are ready to be moved to a cooler, long-term storage location where they can last for several months.