Planting a second crop of potatoes for a fall harvest allows Zone 7 gardeners to maximize their yield outside of the typical spring season. This autumn crop utilizes the cooling temperatures of the late season, which are ideal for tuber development after the summer heat has passed. Successfully growing fall potatoes depends entirely on carefully timing the planting to ensure the tubers mature before the first killing frost. The challenge is providing enough growing time within a shorter, frost-limited window while navigating the hot days of late summer.
Calculating the Optimal Planting Window
Determining the precise planting date requires counting backward from the expected first frost, generally between October 29th and November 15th for Zone 7. Potato varieties suitable for a fall harvest typically require 70 to 90 days to reach a size appropriate for digging. This maturity period places the optimal planting window between late July and mid-August, giving the plants approximately 10 to 12 weeks of growth. Planting too late risks the tubers not fully developing before the ground freezes, while planting too early can expose young plants to excessive heat that inhibits tuber formation.
To gain a time advantage in this compressed schedule, select seed potatoes that have been “chitted,” or pre-sprouted. Chitting involves placing the seed pieces in a well-lit area with moderate temperatures until short, sturdy sprouts emerge. This preparatory step can shave one to two weeks off the time it takes for the plant to emerge, accelerating the initial vegetative growth phase. Focusing on fast-maturing, early-season varieties, such as certain reds or Yukon Golds, further ensures the crop is ready for harvest before the seasonal deadline.
Preparing the Ground and Seed Potatoes
Preparing the soil for late-summer planting provides the immediate resources the plants need for quick growth. The soil should be deeply loosened to at least 10 inches, allowing for easy tuber expansion and improved drainage, which is important in warm, late-season conditions. Potatoes are heavy feeders, and the fall crop benefits from incorporating aged manure or rich compost directly into the planting area for immediate nutrient access. This provides the potassium and phosphorus necessary to support vigorous foliage and tuber development.
If the seed potatoes are large, cut them into pieces roughly the size of a chicken egg, ensuring each piece contains at least one or two “eyes” or growth nodes. After cutting, the pieces must be cured for one to three days in a dark, warm, and well-ventilated space. Curing allows the cut surface to dry and form a protective, calloused layer. This significantly reduces the risk of rot and fungal infections when planted in the often-warm, moist soil of late July or August.
Essential Care for the Fall Growing Season
The initial weeks of the fall growing season coincide with the hottest part of the summer, making consistent moisture the most important factor for success. Potatoes require deep, regular watering, particularly when daytime temperatures exceed 85°F, because heat stress can halt tuber formation and lead to poor yields. Maintaining even soil moisture helps cool the root zone and prevents secondary growth or misshapen tubers that result from cycles of drying and sudden rewetting.
As the potato plants grow, the process of hilling must begin, involving mounding soil or organic material around the emerging stems. Hilling serves the dual purpose of protecting the developing tubers from sunlight, which prevents greening and toxicity, and keeping the surrounding soil cooler. A thick layer of straw or mulch applied around the base of the plants can further moderate soil temperature and reduce water evaporation. Monitoring for common pests like the Colorado potato beetle and diseases like early blight is important in the late season, requiring prompt action to maintain healthy foliage until harvest.
Harvesting and Storage
Harvesting fall potatoes is signaled by the natural dieback of the plant’s foliage, a process known as senescence. The leaves and stems will yellow and begin to wither, indicating the plant has diverted its energy fully into tuber development. If the foliage remains green close to the expected first frost date, manually cut the stems back to the soil line two to three weeks before the frost is anticipated. This action forces the potato to finish forming its skin, which is necessary for long-term storage.
After the foliage has died back or been cut, the tubers should remain in the ground for 10 to 14 days to allow the skin to fully set, a process called curing. Once dug, the potatoes must undergo an initial curing phase by being spread out in a cool, dark, and moderately humid location for about two weeks. This period allows minor cuts or bruises to heal over, providing a protective barrier against pathogens during storage. For long-term preservation, move the cured potatoes to a permanent storage environment that maintains temperatures between 35°F and 40°F, with high humidity and total darkness, to discourage sprouting and shriveling.