Determining the optimal harvest time for potatoes is the most important factor affecting their quality and storage life. Harvest readiness depends entirely on the gardener’s goal: harvesting for immediate, tender consumption or for long-term storage as a mature potato. Immature potatoes have delicate skin and high moisture content, making them unsuitable for keeping. Conversely, a mature potato’s hardened skin allows it to last for months.
Harvesting New Potatoes
New potatoes are small, thin-skinned tubers harvested early in the plant’s growth cycle, prized for their sweet flavor and tender texture. This early harvest typically occurs two to three weeks after the plant has finished flowering, or when the plant reaches about six inches in height. At this stage, the sugars have not fully converted to starch, which contributes to their desirable taste. Because their thin skin is easily damaged, new potatoes are not suitable for long-term storage and must be used within a few days.
A technique called “stealing” allows for harvesting new potatoes without disturbing the main plant. Gently feel around the edges of the plant’s hill to locate the largest tubers near the surface. Carefully pull or twist a few of these smaller potatoes from the stolon. This method leaves the majority of the root system intact, allowing the remaining tubers to continue growing toward maturity for a later main harvest.
Recognizing Maturity for Main Harvest
The main potato harvest targets mature tubers with thick, set skins necessary for successful storage. The clearest sign of maturity is the natural dieback of the above-ground foliage, known as senescence. This occurs when the plant’s leaves and stems turn yellow, brown, and collapse as the plant redirects energy to the developing tubers.
Once the foliage has completely died back, a waiting period is required for the skins to thicken and harden in the soil. This process, called “skin set,” prevents scuffing, bruising, and disease entry during harvest. Gardeners should wait approximately two weeks after the foliage has fully died before digging up the tubers. This delay ensures the skin is firm and extends the potato’s storage life.
The Harvesting and Curing Process
Harvesting must be executed with care to avoid damaging the mature tubers. A spading fork is preferred over a sharp spade because its tines reduce the risk of stabbing or slicing the potatoes. Begin digging well outside the plant’s main stem, often a foot or more away, then gently lift the soil and tubers to expose the crop. Work slowly to unearth all the potatoes, as any left behind may sprout the following season.
After unearthing the tubers, handle them gently and never wash them, as moisture encourages rot during storage. Instead, gently brush off any loose soil while inspecting each potato for damage. Damaged potatoes should be separated and used immediately, as they will not store well and could spread decay to the healthy crop.
The final preparation step is curing, which further hardens the skins and allows minor harvest wounds to heal. Curing involves placing the undamaged potatoes in a dark, cool, and humid location for 10 to 14 days immediately after harvest. Ideal curing conditions are 50 to 60 degrees Fahrenheit with 85% to 95% relative humidity. This period facilitates the formation of a protective layer over small scrapes, ensuring the potatoes are ready for long-term storage.