The potato plant is unique because the edible portion—the tuber—grows entirely underground, hidden from view. Timing the harvest determines both the final yield and the quality of the crop. The plant’s above-ground foliage provides the most reliable cues for when the tubers are ready. Observing these signals ensures potatoes are harvested appropriately for either immediate use or long-term storage.
Harvesting for New Potatoes
New potatoes are young, small tubers harvested before the plant fully matures, prized for their tender texture and delicate flavor. The primary indicator for this early harvest is the appearance of flowers on the plant’s stems. Gardeners can begin a test dig two to three weeks after flowering, when tubers are typically one to two inches in diameter. The technique involves gently reaching beneath the plant’s base to remove a few tubers without fully uprooting the main stem. Since new potatoes have thin, delicate skins, they are not suited for extended storage and should be consumed quickly to maintain freshness.
Visual Signals for Mature Harvest
The most significant signal for a mature, storage-ready crop is the process known as “dieback,” which is the natural aging and dying of the foliage. This phase begins when the plant stops directing energy toward vegetative growth and instead focuses on filling and setting the underground tubers. A healthy, upright green plant will begin to turn yellow, starting at the tips of the leaves and moving inward. This yellowing progresses to browning, until the entire plant stem and leaves wilt, dry out, and collapse onto the soil surface. This dieback indicates that the tubers have reached their maximum size and the plant’s nutrient transfer process is complete.
It is necessary to wait an additional period after the foliage has fully died back before digging, as this time allows the potato skins to “set.” The setting process involves the skin thickening and hardening, which improves the tuber’s ability to resist bruising and disease during storage. A waiting period of two to three weeks after the vines are completely brown and dry is recommended to ensure the skins are sufficiently cured underground. If a potato’s skin rubs off easily when tested, it indicates the tuber is not yet ready for long-term storage and requires more time in the soil.
Digging, Curing, and Storage Preparation
Once the foliage is dead and the waiting period for skin set is complete, the potatoes can be harvested. To avoid damaging the tubers, insert a garden fork or shovel well away from the center of the plant, typically 12 to 18 inches out from the stem. The goal is to gently lever the entire mass of soil and tubers upward, minimizing the chance of piercing the potatoes.
Immediately following harvest, the tubers must undergo curing, which is necessary for long-term storage and quality preservation. Curing allows minor nicks or bruises from digging to heal, forming a protective cork layer over damaged areas. This process also allows the skins to further dry and toughen.
Curing requires placing the freshly dug, unwashed potatoes in a dark, well-ventilated space with high humidity and a temperature between 55 and 70 degrees Fahrenheit for one to two weeks. Before final storage, inspect the potatoes and gently brush off any excess soil. Do not wash the potatoes, as added moisture encourages rot and negatively affects storage life. Potatoes showing signs of damage, disease, or greening should be set aside for immediate consumption.