Determining the precise moment to harvest potatoes significantly impacts the yield, flavor, and potential storage life of the crop. Since the edible portion develops entirely underground, the visible cues above the soil become the primary indicators. Optimal timing depends entirely on the grower’s intended outcome, whether the goal is to enjoy small, tender new potatoes immediately or to store a fully mature main crop. Understanding the difference in readiness signals for these two goals is the first step in a successful potato harvest.
Differentiating Harvest Goals
Potato harvest is divided into two categories defined by tuber maturity: new potatoes and main crop potatoes. New potatoes are young, small tubers harvested early, typically 60 to 80 days after planting, while the foliage is still green. They are valued for their delicate, thin skin and sweet, mild flavor, making them ideal for immediate consumption.
Main crop, or storage potatoes, are left in the ground longer, generally 90 to 120 days or more, until the plant completes its full growth cycle. Harvesting later allows the tubers to reach maximum size and develop a thick, protective skin necessary for long-term preservation.
Identifying Readiness for New Potatoes
New potatoes are ready for harvest once the plant begins its flowering stage, usually about seven weeks after planting. Flowers signal that the tubers have begun to form and are reaching a small size, typically one to two inches in diameter. At this stage, the plant is still green and the tubers are actively expanding.
Growers often wait an additional one to three weeks after flowering before harvesting. Since the plant is still alive, the common technique is to gently “rob” the outer edges of the hill without disturbing the main root system. The skin on a new potato is immature and delicate, rubbing off easily, which is acceptable because these potatoes do not store well and are meant to be eaten quickly.
Key Indicators for Main Crop Storage
The most reliable visual indicator for a mature main crop is the natural die-back of the plant’s foliage, known as senescence. The plant’s leaves and stems will begin to yellow, wilt, and eventually turn brown and collapse. This process signifies that the plant has finished transferring carbohydrates to the tubers, and their growth has ceased.
The critical step for storage quality is to leave the tubers in the ground for a period after the foliage has fully died back. This waiting period allows for a process called “skin set” to occur, where the tuber’s periderm matures and toughens. Skin set strengthens the skin’s attachment to the tuber flesh, which minimizes water loss and protects against bruising and disease during storage.
To confirm the skin has properly set, perform a physical assessment on a test potato. Dig up a single tuber and gently rub the skin with your thumb. If the skin peels, scuffs, or “slips” easily, the potato is not yet ready for long-term storage and needs more time underground.
For optimal skin set and maximum storage life, allow the potatoes to remain in the soil for 10 to 14 days after the vines are completely dead. Harvesting before this period, when the skin is delicate, leads to a higher risk of scuffing injuries and rapid water loss in storage.