Growing a second crop of potatoes after the spring harvest is often referred to as a fall or second-season planting. This is advantageous in regions with long, mild autumns or where summers are too hot for mid-season potato development. Potatoes are a cool-season crop that thrives when temperatures are moderate, making the transition from late summer into fall an ideal growing window. Successful fall cultivation relies on precise timing, variety selection, and the careful management of late-season weather challenges.
Feasibility and Timing the Second Planting
The success of a fall potato crop hinges on accurately predicting the first average frost date for your specific location. To determine the correct planting window, count backward from this expected frost date, allowing for the variety’s required maturity time, plus a buffer. Most short-season potato varieties require 70 to 90 days from planting until they reach a mature, harvestable size. Planting too late means the tubers will not fully size up before the ground freezes, while planting too early risks exposing the young plants to the high heat of late summer.
Tuber formation slows or stops entirely when the soil temperature consistently exceeds 80 degrees Fahrenheit, which is a common challenge during mid-summer planting. Therefore, the calculated planting date must allow the plants to establish themselves during the final weeks of summer heat, with the bulk of their tuber development occurring as soil temperatures naturally cool in the fall. In warmer climate zones, such as USDA Zones 8 through 10, planting often occurs in August or September, avoiding the most intense heat while still allowing for a sufficient growing period. Gardeners in cooler regions may still achieve a fall crop by using season extenders like cold frames or row covers.
Selecting the Right Potato Varieties
Choosing a potato variety with a short maturity window is essential for a fall crop, as the season is compressed between summer heat and winter cold. Look for “early maturity” or “short-season” types, which typically mature in 60 to 80 days. Suitable examples include ‘Yukon Gold,’ ‘Red Pontiac,’ ‘Purple Viking,’ and ‘Dark Red Norland.’ Selecting a quicker-maturing variety ensures the tubers have sufficient time to develop before the plant’s foliage is killed by frost.
It is recommended to purchase certified seed potatoes for the fall planting, rather than using potatoes saved from your spring harvest. Spring-harvested tubers often enter a natural dormancy period that prevents them from sprouting immediately, causing significant delays in your short fall window. If you must use saved stock, you can encourage them to break dormancy and sprout, a process known as chitting, by placing them in a warm, well-lit area for a week or two before planting. This step confirms the seed potato is actively ready to grow and will not delay the crop.
Essential Planting and Growing Techniques
Preparing the soil properly is important because the plant must establish quickly in the late summer heat. Potatoes require loose, well-draining soil that is rich in organic matter to allow the tubers to expand easily. Plant the seed pieces deeper than you would for a spring crop, typically 5 to 6 inches deep, to help insulate them from the high late-summer soil temperatures. This deeper planting assists in keeping the developing root zone cooler, which encourages more vigorous early growth.
Once the potato plants emerge and reach about 6 to 8 inches tall, begin the process of hilling, or mounding soil around the stems. Hilling serves two primary functions: it prevents sunlight from reaching the developing tubers, which causes them to turn green and inedible, and it provides a greater surface area for new tubers to form. Continue to add soil or mulch around the stems as the plant grows, covering all but the top few inches of foliage. Maintaining consistent soil moisture is necessary during the initial hot phase, but avoid overwatering, as overly saturated conditions can lead to rot.
Protecting the Crop and Harvesting
As the season progresses, the primary focus shifts to protecting the developing crop from the first hard frost, which can kill the foliage prematurely. While a light frost may only damage the leaves, a hard freeze can compromise the plant’s ability to provision the tubers. To guard against early cold, apply a thick layer of straw or mulch over the plants, or use temporary coverings like row covers or old blankets when frost is forecast. Covering the plants traps latent heat from the soil, providing a protective buffer for the above-ground growth.
The potatoes are ready for harvest once the plant’s foliage naturally begins to yellow and die back, typically around 90 days after planting. This process, called senescence, signals that the plant has finished transferring its energy to the underground tubers. Wait until the foliage has fully died down to allow the potato skins to thicken, or “set,” which significantly improves their storage life. Dig carefully around the plant’s perimeter using a garden fork to avoid puncturing the tubers. Allow the harvested potatoes to cure in a dark, humid, and well-ventilated space for about two weeks before moving them to long-term storage.