The potato is a versatile tuber crop, and knowing precisely when to harvest it is paramount for achieving the best results. Optimal timing directly dictates the potato’s flavor, size, and viability in storage. Treating the plant’s lifecycle as multiple harvest windows is key to maximizing the crop’s potential. Aligning the harvest with the intended use—whether for immediate eating or long-term keeping—ensures the highest quality and prevents spoilage.
Harvesting Timing for New Potatoes
“New potatoes” are young, immature tubers defined by their small size and thin, delicate skins. Harvesting them early allows for a tender texture and a fresh, milder flavor distinct from mature potatoes. These smaller spuds are not a separate variety but are harvested before the plant’s energy has been fully dedicated to tuber growth.
The visual cue for this initial harvest window is the plant’s flowering stage, usually occurring 60 to 70 days after planting. Wait two to three weeks after the plant has finished blooming before checking for size. At this point, the tubers have formed but lack the thick, protective skin needed for extended storage.
New potatoes are harvested selectively, allowing the rest of the plant to continue growing. Gardeners can gently feel around the base of the plant or carefully dig up only a few tubers from the outer edges of the hill. The remaining potatoes are left undisturbed to continue their maturation process, providing a staggered harvest throughout the season.
Harvesting Timing for Storage Potatoes
Potatoes intended for long-term storage must be fully mature, marked by a tough, set skin. The most reliable visual indicator of maturity is the complete die-back of the foliage. The green vines will yellow, wither, and collapse, signaling that the plant has finished its growth cycle.
Once the vines have fully died back, a mandatory waiting period of two to three weeks is necessary before digging. This time allows the potato skins to “set” or thicken, a process called suberization. A mature, suberized skin acts as a protective barrier against bruising, moisture loss, and disease during storage.
Testing for maturity involves gently digging up a test tuber and rubbing the skin with a thumb. If the skin easily rubs off or “feathers,” the potato is not yet ready, and harvesting should be delayed for another week. Harvesting before this skin-set process is complete results in tubers that shrivel and rot quickly, making them unsuitable for winter storage.
Techniques for Successful Harvesting
Removing the tubers requires precision and care to prevent physical damage, a primary cause of storage loss. Using a spading fork rather than a sharp shovel is recommended, as the blunt tines are less likely to pierce the potatoes. The fork should be inserted into the soil at least 12 to 18 inches away from the main stem of the plant.
Digging well outside the immediate base of the plant ensures you avoid the main cluster of tubers, which can extend surprisingly far. Gently lever the soil and the plant upward, then carefully search through the loose dirt by hand to locate all developed potatoes. Handling the tubers gently minimizes bruising, which can initiate decay even if the skin is not broken.
After extraction, gently brush off the clinging soil, but resist washing the potatoes. Introducing moisture before curing can shorten their storage life by increasing the risk of bacterial soft rot. Any potatoes cut, bruised, or damaged during digging should be set aside for immediate consumption, as they will not store well.
Preparing Potatoes for Long-Term Storage
Immediately following harvest, mature potatoes must undergo curing, their first line of defense against decay. Curing involves holding the tubers in a dark, warm, and highly humid environment for ten to fourteen days. Ideal conditions are a temperature range of 50 to 60°F (10 to 15°C) with 85% to 95% relative humidity.
The purpose of curing is twofold: to allow minor nicks sustained during harvest to heal and to strengthen the skin. In this environment, the potato forms a new layer of protective skin, or periderm, over damaged areas. This seals the wound, prevents moisture loss, and determines the tuber’s ultimate storage life and resistance to pathogens.
Once cured, potatoes should be moved to long-term storage conditions that prioritize a cool, dark, and humid environment. The optimal temperature for long-term keeping is 35 to 40°F (2 to 4°C), paired with high humidity to prevent shriveling. Storing them in darkness is necessary to inhibit the development of chlorophyll and the toxic compound solanine, which causes greening.