The sweet potato, a warm-weather tuber of tropical American origin, thrives in the long, hot growing season provided by Texas. Its cultivation is widespread and generally successful in both commercial agriculture and home gardens across the state. Determining the exact moment to lift the crop from the soil remains the primary challenge for many Texas growers. The correct harvest time is a flexible window based on the plant’s maturity, local climate conditions, and the need for immediate post-harvest preparation.
Knowing When the Tubers Are Ready
The most reliable indicator for when sweet potato tubers are ready rests on the plant’s biological signals and the number of days since planting. Most popular commercial varieties, such as ‘Beauregard’ and ‘Covington,’ require a growing period ranging from 90 to 135 days to fully mature. Growers should check the specific days-to-maturity for their variety and use that timeline as a guide for when to begin monitoring the crop.
A visible sign of approaching maturity is when the vigorous vines begin to turn yellow, often around the plant’s crown. This indicates the plant is shifting energy away from foliage production and toward tuber enlargement. This yellowing suggests the tubers are near their full size, and they will continue to grow as long as conditions allow. Unlike traditional potatoes, sweet potatoes can remain in the ground past the estimated maturity date to increase size, provided the soil temperature remains warm.
The absolute deadline for harvesting sweet potatoes is the arrival of a “killing” frost (a temperature drop below 32°F). Sweet potatoes are highly sensitive to cold, and a frost that kills the vines can quickly cause chilling injury to the tubers just beneath the soil surface. Soil temperatures that fall below 50°F to 55°F can cause internal decay and a hard core to develop, ruining their storage potential. Therefore, all roots must be lifted from the ground immediately before or directly after the first frost event in a region.
How Planting Dates Affect Regional Harvest Windows
The vast size of Texas creates variable planting and harvest calendars, shifting the ideal harvest window by several weeks depending on the geographic region. Sweet potato slips must be planted when the soil temperature consistently reaches 65°F, which occurs much earlier in the southern part of the state. This regional variation in planting time directly dictates the corresponding harvest season, even for the same variety.
In South Texas and along the Gulf Coast, planting can begin in March or April, as the last spring frost can occur as early as February. This early start allows for an early harvest window, often beginning in August and continuing through September for standard 100-day varieties. Coastal regions typically see their first frost much later, sometimes not until late December, providing a long, flexible growing season.
Conversely, in North Texas, including the Panhandle and areas around Dallas, the last frost is closer to late March or April. Planting is delayed until mid-to-late May to ensure the soil has warmed sufficiently, which pushes the harvest season back into the cooler months. Growers in these zones typically plan to harvest in October, with the deadline being the expected first frost of mid-November. The harvest window is condensed, requiring monitoring of the weather forecast in the late fall.
Proper Digging and Curing for Storage
Once the optimal timing is determined, the physical removal of the tubers requires a careful technique to prevent skin damage, as the skin is delicate at this stage. It is beneficial to cut the vines back a day or two before harvest to make the digging process easier and help slightly toughen the skin. The best tool is a garden fork or shovel, which should be inserted into the soil at least 12 to 18 inches away from the central plant crown.
This distance helps to avoid spearing or slicing the tubers, which often grow horizontally away from the main stem. The soil should be gently loosened in a wide circle around the plant, and the entire clump of roots should be lifted carefully to minimize bruising. Any damage to the skin, even minor abrasions, introduces pathways for rot and reduces the tuber’s ability to be stored long-term.
Immediately following the harvest, sweet potatoes must undergo curing to be properly preserved and to develop their signature flavor. Curing involves keeping the roots in a high-temperature, high-humidity environment for approximately four to fourteen days. The ideal conditions are a temperature range of 80°F to 85°F with a relative humidity of 80% to 95%.
During this curing period, wounds and minor cuts on the skin heal over, forming a protective cork layer that prevents moisture loss and decay. The heat facilitates the conversion of starches within the tuber into complex sugars, increasing the sweet potato’s sweetness and palatability. After curing, the roots should be moved to a cooler storage area, ideally maintained at 55°F to 60°F, to maximize their shelf life.