The decision of when to harvest potatoes is more complex than simply digging them up when the plant looks mature. Correct timing is necessary for determining the quality of the final product, influencing both flavor and potential for long-term storage. Harvesting at the wrong time can result in thin-skinned tubers that spoil quickly or a significantly reduced yield. Understanding the plant’s life cycle and your specific goal, whether for immediate consumption or winter keeping, guides the entire process.
Visual Signals of Readiness
The most reliable indicator that potato tubers have finished their main growth phase is “haulm dieback,” which is when the foliage (vines) yellows, wilts, and eventually turns brown and dies. When the plant’s tops begin to senesce, they are no longer actively sending energy to the tubers for growth.
For potatoes intended for storage, the haulm must be completely dead and dry before harvesting. Once the foliage is fully dead, allowing the tubers to remain in the soil for an additional one to three weeks is beneficial. This waiting period allows the potato skins to thicken and “set,” making them more durable and resistant to bruising. To test for skin set, gently rub the skin with your finger; if it does not easily rub off, the potato is ready for harvest and long-term keeping.
Harvesting for New Potatoes vs. Storage
The primary harvest goals are divided into two categories: new potatoes and storage potatoes, differentiated by maturity and intended use. New potatoes are young tubers harvested while the plant is still green and actively growing, often two to three weeks after the plant has flowered. They are prized for their small size and delicate, thin skins.
Because their skins are thin, new potatoes do not store well and should be consumed within a few days of harvest. In contrast, storage potatoes are left in the ground until the plant has completed its life cycle, allowing the tubers to reach maximum size and develop a tough, protective skin. This mature, thicker skin prevents moisture loss and decay, making them suitable for keeping through the winter.
Technique for Digging and Minimizing Damage
The physical act of harvesting requires careful attention to avoid damage, as any puncture or slice provides an entry point for disease and rot. A garden fork is preferred over a sharp shovel because the tines are less likely to slice a tuber than a solid blade. Begin digging several inches away from the main stem, working outside the expected cluster of potatoes.
Carefully lift the entire plant and surrounding soil, gently sifting through the loosened dirt by hand to locate all the tubers. Avoid pulling the vines, as this can separate the potatoes from the stem and leave many behind. Harvest on a dry, warm day; this helps ensure the soil is loose and the potatoes are relatively dry, reducing the risk of skin damage during removal.
Curing and Preparing Potatoes for Storage
Once harvested, any potato intended for long-term keeping must undergo curing. This step heals minor scrapes, nicks, or bruises that occurred during digging and further toughens the skin. Curing involves placing the potatoes in a dark, well-ventilated area with high humidity, typically between 85 to 95 percent.
The ideal temperature range for curing is 50 to 60 degrees Fahrenheit, maintained for one to two weeks. After curing, the potatoes should be moved to their final storage location, which must be cool, dark, and humid to prevent sprouting and shriveling. Storage conditions should be kept around 40 to 45 degrees Fahrenheit to ensure the tubers remain dormant for months.