The success of a potato harvest, whether in the high-altitude valleys or the lower plains of Colorado, relies on precise timing. Potatoes are an unusual crop because their development is hidden underground, making the correct moment to dig them up a matter of observation and waiting. Knowing when to harvest is crucial for the quality, flavor, and longevity of the crop, especially for home gardeners aiming to maximize their yield from Colorado’s diverse and often short growing seasons. The decision to harvest can drastically change the resulting tuber, separating a tender “new potato” from a fully mature, long-storing main crop.
Differentiating Harvest Timings
The timing of potato harvest depends entirely on the intended use, allowing for two distinct harvest windows. Gardeners can choose to harvest young, thin-skinned “new potatoes” early in the season, or wait for the full maturation of the tubers for long-term storage. New potatoes are typically ready for harvest around 60 to 70 days after planting, often appearing about two to three weeks after the plant finishes flowering. These tubers have a high moisture content and a delicate skin that rubs off easily, which makes them ideal for immediate consumption but unsuitable for extended storage.
For a mature crop intended for storage, the timeline extends significantly, usually falling between 90 and 120 or more days after planting. This longer period allows the tubers to reach their full size and develop a thick, protective skin, a process known as “setting the skin.” The thickened skin is necessary for the potatoes to withstand the handling and conditions of a cool-weather storage environment. Mature potatoes are higher in starch and possess a more robust texture.
Visual Indicators of Readiness
The most reliable sign that mature potatoes are ready for harvest comes from the plant’s foliage, not the calendar. Gardeners should watch for the natural process of senescence, where the vibrant green leaves begin to yellow and eventually brown. This “dying back” indicates that the plant is redirecting its energy away from foliage production and into the final bulking and skin-setting of the tubers underground.
For a mature, storable crop, it is recommended to wait until the foliage has completely died back and withered. After the vines have fully browned, a waiting period of one to three weeks is observed before digging. This waiting period in the ground allows the skin to fully harden, ensuring the best possible quality for storage. A simple test is to gently rub the skin of an unearthed sample potato; if the skin does not easily rub off, the potatoes are ready.
Digging Techniques and Climate Considerations
When the time comes to harvest, proper digging technique is essential to avoid damaging the tubers, which compromises their storage life. A spading fork, rather than a shovel, is the preferred tool because its tines are less likely to slice through a potato. The tool should be inserted into the soil well away from the main stem, about six to twelve inches out, to ensure the tines do not pierce the cluster of potatoes directly beneath the plant. The gardener then gently loosens the soil and lifts the entire clump of earth, carefully sifting through the dirt to find all the buried tubers.
Climate Considerations
In Colorado, climate factors are an overriding concern that can force a harvest regardless of the plant’s visual cues. In high-altitude growing regions like the San Luis Valley, gardeners must harvest before a hard frost penetrates the soil, which can quickly turn the potatoes to mush. A light frost on the foliage is acceptable and even encouraged, as it helps kill the vines and promotes skin set, but a prolonged or deep freeze is detrimental. Furthermore, the soil should be relatively dry during harvest, so stop watering one to two weeks before digging; harvesting from overly wet soil can encourage rot.
Preparing Potatoes for Long-Term Storage
Immediately following harvest, potatoes intended for winter storage must undergo a process called curing. Curing is a period of rest that allows any minor scrapes or bruises from the digging process to heal, which is necessary for preventing decay. This involves placing the unwashed, soil-covered potatoes in a dark, well-ventilated space for one to two weeks.
The ideal environment for curing is a moderately warm temperature, typically between 60 and 65 degrees Fahrenheit, with high humidity. Once cured and the skins are firm, the potatoes are ready for long-term storage in a cool, dark location. The storage temperature should be lowered to a range of 40 to 46 degrees Fahrenheit, such as in an unheated basement or root cellar. Maintaining high humidity in the storage area is important to prevent the tubers from shriveling over time.