Mulching sweet potato plants with black plastic helps keep the soil as warm as possible. It also prevents the vines from setting down more roots as they grow, which takes energy from tuber formation. If you are not using plastic, lift the vines from time to time to break off the roots that form along the stem.
The foliage on regular potato plants tends to die back when the spuds are ready to harvest. Sweet potato plants keep on growing until the temperatures get too chilly. Let them grow as long as possible (at least 120 days), but be sure to harvest the tubers before the first heavy frost. Cold temperatures can damage the sensitive tubers. You’ll find sweet potatoes are easier to dig than regular potatoes because the tubers tend to cluster more closely to the stem. As you harvest, treat the tubers gently because the skin is thin and the flesh bruises easily.
Once harvested, let your sweet potatoes air dry for several hours, then nestle them into a shallow basket or ventilated box, lined with dry newspaper. The tubers should then be “cured” for 10 to 15 days at 80 to 85 degrees (a warm, dark attic is ideal). The optimum temperature range for storage after curing is 55 to 60 degrees.
