Unlike regular potatoes, sweet potato prefers the warmest growing conditions. In fact, they like it hot, so we suggest waiting at least 2 to 3 weeks after the last frost to plant them. This will allow the soil to warm to a temperature more amenable to growing. Covering the bed with black plastic prior to planting and then planting through the plastic can speed the process for those with a shorter growing season or for those in a hurry to get them in the ground.
Growing Sweet Potatoes in the Garden
Soil, Water & Light Requirements Sweet potatoes are very adaptable, although you should be aware the tubers (the edible roots) can be deformed when grown in heavy clay. On the other hand, very sandy soil can result in long, stringy tubers. If one of those is your soil type, amending the soil to a depth of about one foot should alleviate that problem and help to ensure a good-looking, palatable crop. Don’t know your soil type? This article will help you determine what type you have by simply using a canning jar: Simple Soil Test.
Regardless of where you grow your sweet potatoes, the amount of sunlight is critical. Sweet potatoes will grow best with 8 hours or more of direct sunlight. Regular, weekly, deep watering will yield the best crop. Be sure to monitor the soil moisture, especially if you are experiencing droughty conditions. As harvest time approaches, cut back on watering; overwatering at this time can cause cracking of your tubers. Take the guesswork out of monitoring with a moisture tester.
Spacing, Fertilizing & Weed Control Sweet potatoes need a lot of room to grow, so plan accordingly. Most gardeners have the best results by building 10-inch-high ridges or hills with approximately 3 to 4 feet between them; leave 12 to 18 inches between each plant, and bury each plant right up to the bottom leaves, tamping down firmly, but not overly hard. If planting through plastic, build the hills/ridges first and then cut a hole at least 6 inches in diameter at each place where you want a plant. If not using plastic, we recommend you mulch around the vines about 2 weeks after planting in order to discourage weed growth and to conserve moisture. This will also help to keep the soil loose, which aids in the most desirable development of the tubers. To prevent secondary rooting, regularly lift the vines where they touch the ground as they spread. Fertilize with a low-nitrogen fertilizer when transplanting and then us a balanced organic fertilizer every 2 weeks throughout the growing season. Avoid nitrogen-rich fertilizers, as these will produce fantastically gorgeous leaves, but tinier tubers.
Harvesting, Curing & Storage As soon as the leaves start to turn yellow, you can begin harvesting, though leaving them in the ground longer will result in the highest yield and tastier tubers. They should be harvested before the first fall frost. The best time to harvest is when the day is sunny and the soil is relatively dry. Most growers will tell you to cut the vines back to about 12 inches just before harvesting. This clears the field to avoid digging too close to the crown of the plants and possibly damaging the tubers. Then, using a spade or fork, carefully loosen the soil starting out about 18 inches from the crown of each plant and digging down at least a foot. Work around the entire plant, gently loosening the soil, and then pull gently on the crown and gather in those gorgeous sweet ‘taters with your hands.
Sweet potatoes should be cured prior to storage and use. First, separate the bruised or cut tubers: they can be used right away. Next, lay the unwashed sweet potatoes in a warm, well-ventilated, shaded spot for about 10 days. If such a spot is not available, they can be cured inside by placing them near a furnace for 2 to 3 weeks. Once cured, wrap each tuber individually in newspaper and pack carefully in a wooden box or basket. Treat them gently as you do this, as they bruise easily. Now store them in the coldest room or basement. The ideal storage temperature is between 50° and 60°F. If cured and stored properly, some varieties will store up to 6 months.
Sweet Potatoes in Containers
Sweet potatoes can also be grown in containers to save space. The water, sunlight and nutritional requirements will be the same as for garden growth, although in a container they will most likely need more water, and more often. When the soil is dry to an inch from the top, water well.
Container Size & Drainage Your sweet potatoes will need at least a 5-gallon container to grow well. If your potting soil does not already contain fertilizer, mix some into the soil prior to planting. Ensure the container has proper drainage. If not, drill a few 1/2-inch holes in the bottom. Fill the container with your potting soil to within an inch of the top, and then plant 1 or 2 plants in individual holes, as described above.
Harvesting You can follow the advice above, taking extra care not to damage the tubers as you dig, or you can simply dump the container and pull your treasures from the pile. Use the dumped soil to fill in holes in the yard, spread it to amend your lawn or add to your compost bin. It’s best to start fresh or to plant a non-potato-related vegetable in that container for next year if you are reusing the soil. If you’ve experienced any disease, discard it completely and clean the container with a 4 to 1 mixture of water and bleach. Cure and store your sweet potatoes as described above.