Planting potatoes in August is a viable option for a second, fall harvest. This late-season planting is typically only successful in regions that experience long, mild autumns, generally corresponding to USDA Hardiness Zones 7 and warmer. The August timing requires gardeners to plan around two environmental challenges: the lingering high heat of summer and the eventual arrival of freezing temperatures. Success relies on strategic variety selection and specialized care to ensure tubers develop before the growing season ends.
Determining the Fall Planting Window
Calculating the planting date requires working backward from the expected first hard frost date for the specific region. Quick-maturing varieties generally need 70 to 90 days to reach a harvestable size. Gardeners must allow for this full maturation period plus a buffer to compensate for potential heat-induced dormancy during establishment.
Planting in August is common in warmer climates, such as USDA Zones 7 and 8, where the growing season extends well into November or December. The subsequent cooling temperatures of fall provide the ideal environment for tuber development. Attempting an August planting in colder zones with an early October frost date makes the window too short for a meaningful harvest. The cooler night temperatures that arrive in early fall signal the plants to begin tuber formation and bulking.
Choosing Seed Potatoes and Preparing the Site
For an August planting, selecting quick-maturing varieties is necessary to ensure the crop finishes before a killing frost. Varieties classified as “early season” or “second early” are often the best choices. It is important to source certified, disease-free seed potatoes, rather than planting leftover potatoes from a spring harvest, as these may be dormant or carry diseases.
Site preparation must focus on creating a cool, loose environment that encourages immediate growth despite the summer heat. Potato plants prefer loose, well-draining soil that is rich in organic matter. Before planting, the soil should be thoroughly loosened and amended with compost. For August planting, some gardeners temporarily shade the planting area or heavily pre-water the ground to lower the soil temperature slightly, counteracting heat that can inhibit initial sprouting.
Planting and Care Techniques for Summer Heat
The August planting process requires modifications from typical spring methods to insulate the seed potatoes from high temperatures. Planting the seed potatoes deeper than the standard spring depth, typically around six inches, helps keep the tubers and developing roots in cooler soil. Tuber development is inhibited when the soil temperature exceeds 75°F, so deeper planting acts as a thermal buffer against surface heat.
Consistent and substantial moisture is required during the hot establishment phase. Daily watering may be necessary to keep the soil consistently cool and moist, preventing the plants from entering heat-induced dormancy. The first hilling—mounding soil around the emerging green shoots—should be performed promptly after the foliage appears. Subsequent hilling should be heavy and frequent, protecting the developing tubers from sun exposure and acting as insulation against high soil temperatures.
The late-season planting window also means monitoring for pests and diseases that thrive in late summer humidity. Fungal diseases, such as late blight, can be a risk, requiring vigilance to manage infestations quickly. As temperatures cool in September and October, the plants transition from focusing energy on foliage to bulking up the underground tubers. Maintaining proper moisture levels throughout this bulking period is essential for a good yield.
Harvesting the Fall Crop
The timing of the fall harvest is dictated by the weather, specifically the threat of a hard freeze. A light frost that kills the foliage is acceptable and can signal that the tubers are ready. However, the crop must be fully harvested before the ground freezes solid. A hard freeze can damage the potatoes underground, causing them to turn to mush.
Visual cues for harvest include the natural yellowing and dying back of the potato foliage, which indicates the plant has diverted its energy into the tubers. Once the foliage has died back, the potatoes should be left in the ground for about two weeks to allow the skins to “set” or thicken, improving their storage potential.
After gently digging the potatoes, they require a curing period of about 10 to 14 days in a dark, cool, and humid location with temperatures between 50°F and 60°F. This curing process allows minor skin damage to heal and further toughens the skin. Properly cured fall-harvested potatoes can be stored in a cool, dark, and frost-free area for several months.