Sweet potato garden.
image by Jennifer Dickert/flickr.com
Sweet potatoes (Ipomoea batatas) are warm-weather vegetables that require a long, warm growing season. Sweet potatoes are tropical vegetables, so they grow the easiest in southern states. It is possible to grow sweet potatoes in the north as well, given proper weather and conditions. Sweet potatoes are high in vitamin A. There is no actual relation to the yam (Dioscorea sp.), due to popular belief. They are of entirely separate species that is grown only in tropical areas.
Choose the variety of sweet potato you would like to plant and purchase the slips (sprouts that sweet potatoes grow from). Sweet potato slips are found more commonly in the southern States, so if you have trouble locating them at local nurseries, check mail order options. You may opt to use transplants as well. See Resources for a variety listing.
Plan the garden site in a place that has full sunlight and well-drained soil. Use a tiller to loosen the soil 12 to 15 inches deep, once the last frost has passed. Mix in a 2 to 4-inch layer of compost. Optimal soil temperatures are between 70 and 80 degrees Fahrenheit. You want the soil to be moist, but never waterlogged.
Plant the slips or transplants 4 inches deep and in the soil using a spade. Ensure plants have 8 inches between them and the rows are 3 feet apart. Firm the soil around the slips or transplants and make a shallow depression around each plant.
Water the beds generously for the first few days. The plants will need 1 inch of water per week, via rainfall or irrigation. Water until the soil is moistened approximately 6 inches deep. Do not water during the last 3 to 4 weeks before the harvest, especially if you plan to store part of the harvest. Place black plastic mulch over the bed approximately 4 to 5 weeks after planting, to speed growth and control weeds.
Aim to harvest approximately 120 days after planting them. Harvest the potatoes on a dry and overcast day, or make sure to shade the roots from direct sunlight. Cut the vines before digging up the potatoes. Handle the potatoes with care while harvesting, as they easily bruise. Allow the potatoes to dry on the ground for a few hours.
Cure the sweet potatoes to heal wounds and convert some of the starch to sugar. The best curing conditions are 85 to 90 percent humidity for one week. If you are unable to achieve those conditions, keep the potatoes in the warmest place in the house (most likely the kitchen) for 14 days. Try to keep the temperature above 70 degrees Fahrenheit.
Store the potatoes in a cool place, but never below 50 degrees Fahrenheit. Do not refrigerate the potatoes. Potatoes should last for at least six months in good storage conditions.