The extended season of USDA Hardiness Zone 7, characterized by mild winters and early springs, provides a planting window that allows for both early summer harvests and substantial late-season yields. Achieving a successful potato crop depends entirely on knowing the precise moment to dig, a timing decision dictated by the intended use of the tuber. This guide focuses on the specific visual cues and calendar dates necessary to time your harvest perfectly in Zone 7.
Differentiating New Potatoes from Storage Potatoes
The initial decision when harvesting is determining whether you are aiming for a “new potato” or a “storage potato.” New potatoes are immature tubers harvested early while the plant’s foliage is still green and vigorous. These young potatoes have a delicate, thin skin that is easily rubbed off, making them tender for immediate consumption. Because their thin skin provides little protection against moisture loss or spoilage, they require refrigeration and should be used within about ten days of harvest.
Storage potatoes are left in the ground until the plant has fully matured and died back, a process known as senescence. This extended time allows the tubers to grow to their maximum size and develop a thick, protective skin. This mature skin is necessary for the curing process and provides the durability needed for months of storage. The timing of the harvest directly links the plant’s life stage to the potato’s ultimate purpose.
Recognizing the Visual Cues for Harvest
The potato plant gives clear visual signals indicating when the tubers are ready for harvest. For new potatoes, readiness typically appears around 7 to 8 weeks after planting, often coinciding with the plant’s flowering stage. If your variety flowers, you can gently probe the soil around the base of the plant once the blossoms fall to check for marble- to golf-ball-sized tubers. Harvesting new potatoes selectively allows the main plant to continue growing, but removing too many early will reduce the final yield.
The signal for harvesting storage potatoes is the complete die-back of the foliage. This process, called senescence, begins when the leaves turn yellow, wilt, and eventually collapse, indicating the plant has finished directing energy toward tuber growth. Once the vines are entirely brown and dead, leave the potatoes in the ground for an additional two weeks. This waiting period allows the potato’s skin to set or toughen up, which maximizes storage life. You can test the skin by digging up a single potato; if the skin easily rubs off, the tuber needs more time underground to mature.
The Zone 7 Specific Harvest Calendar
Zone 7’s mild climate allows for an earlier planting window than many other regions, directly influencing the harvest timing. Gardeners can plant seed potatoes as early as late February or March, provided the soil temperature has reached at least 45°F. This early start pushes the new potato harvest window into the late spring and early summer. New potatoes are typically ready for harvest from late May through mid-June in Zone 7.
This earlier planting also moves the primary storage potato harvest forward, ideally allowing it to finish before the intense heat of late summer. Storage-ready potatoes, which mature 90 to 120 days after planting, are generally ready to be dug from late July through August. Harvesting before the peak summer heat or heavy early fall rains is beneficial, as dry soil makes the harvest easier and reduces the chance of damaging the tubers. It is best to harvest on a warm, dry day to prevent bruising and rot.
Curing and Storing Your Potato Crop
Immediately following the harvest of mature tubers, curing must take place to prepare the potatoes for long-term storage. Curing involves holding the potatoes in a specific environment for 10 to 14 days, allowing minor surface wounds and bruises to heal. This healing process involves suberization, which thickens the skin and increases the potato’s resistance to decay.
The ideal curing environment requires high relative humidity (85% to 95%) and a moderate temperature range of 45°F to 60°F. After the curing period, the potatoes are ready for long-term storage. Storage requires a cool, dark location, ideally with temperatures maintained between 40°F and 45°F, and high humidity (around 90%). Storing potatoes above this temperature range can lead to premature sprouting. Temperatures below 40°F can cause the starches to convert to sugar, resulting in an undesirable sweet flavor.