The potato (Solanum tuberosum) is a widely cultivated staple crop. Determining the exact time required to grow potatoes is highly variable. This variability stems from genetic differences between potato types and the influence of local growing conditions. The timeline is measured from the moment the “seed potato” is planted until the tubers are ready to be harvested, a period that can range from a little over two months to nearly five months.
General Timeline Based on Variety Classification
The primary factor dictating the growth timeline is the classification of the variety planted, which falls into three main maturity groups defined by the days required to reach a harvestable size.
The earliest varieties, often referred to as First Early or New Potatoes, are ready for harvesting approximately 60 to 90 days after planting. They produce smaller tubers with thinner skins that are best consumed immediately rather than stored long-term.
The next group is the Second Early or mid-season potatoes, which offer a balance between a quick harvest and a larger yield. These varieties usually require about 90 to 110 days to reach maturity, allowing for a slightly larger harvest of tubers compared to the first early types.
Finally, Main Crop or Late Season potatoes require the longest growth period, often needing 110 to 140 days, and sometimes up to 150 days. These varieties dedicate more time to the bulking phase, resulting in the largest yields and the thickest skins, making them the most suitable types for long-term storage.
Environmental Factors Influencing Growth Speed
While variety classification sets the expected timeline, environmental factors can accelerate or delay the potato’s development. Soil temperature governs the two most important phases: sprouting and tuber initiation. Optimal soil temperatures for root development and tuber formation are between 59°F and 68°F (15°C and 20°C). Tuber development slows considerably above 68°F (20°C) and can nearly cease if it exceeds 86°F (30°C).
Water availability affects the growth rate and quality of the final product. Potatoes are shallow-rooted plants, making them sensitive to drought. Extended periods of drought or excessive moisture introduce stress that delays maturity or causes defects like cracked or malformed tubers.
Proper sunlight exposure is necessary because the foliage must efficiently perform photosynthesis to generate the energy required for the tubers to bulk underground. A lack of sunlight directly reduces the plant’s ability to produce starch, slowing overall growth and extending the time to maturity.
Determining the Optimal Harvest Time
The decision to harvest is determined by observing the above-ground plant, which signals the completion of the tuber-bulking process. The goal for harvesting “new potatoes” differs from the goal for collecting storage potatoes.
New potatoes are typically ready roughly 7 to 8 weeks after planting, often coinciding with or shortly after the plant flowers while the vines are still green. These young potatoes have thin, delicate skins that rub off easily and must be consumed quickly as they do not store well.
For full maturity and long-term storage, growers must wait for the plant to enter senescence, the natural dieback of the foliage. This process begins when the leaves turn yellow, wilt, and eventually die completely.
After the vines have fully died back, a waiting period of 10 to 21 days is important for “skin setting.” This involves the periderm, or outer skin layer, hardening and tightening around the tuber. This makes the potato resistant to damage and moisture loss during storage, indicating it is fully mature and ready for keeping.