Sweet potatoes, scientific name Ipomea batatus, is a tropical plant that is grown for its starchy sweet roots. Native to South America, sweet potatoes are rated as the seventh most important food crop in the world. Sweet potatoes are commonplace in the diets of many Americans. They are not related to the common potato or yam.
Sweet potatoes can be grown from seed; however, when commercial farmers refer to seeds, they usually mean vine or root cuttings. These are called slips; they are selected from superior plants. It is essential that only high quality slips are used because this determines the yield and quality of the sweet potato at harvest. Many different growers sell state-certified seed sweet potatoes that are guaranteed to produce only the highest quality vegetables if grown properly. It may also be wise to save slips from the previous year's crop to supplement seed purchases.
Sweet potatoes like a light sandy loam that is not too organically rich. Light soils produce the best-shaped sweet potatoes that are desired by consumers. Sweet potatoes will suffer from fungal infections and rot if the soil is prone to flooding or stays too moist. Do not plant them in fields that have had sweet potatoes within the previous two to three years to avoid potential disease problems. Soil with a pH range of 5.8 to 6.2 is optimal for large scale production.
To save growing time and increase production, pre-sprout the seed stock from the previous year's harvest in a specialized sprouting room. Air temperatures should range from 70 to 80 degrees Fahrenheit with a 90 to 95 percent relative humidity. Make sure there is adequate ventilation and airflow. A way to check for adequate oxygen levels is if a lit match can continue to burn without going out. Do not let the humidity get too high; a relative humidity level close to 100 percent can potentially lead to rot. Pre-sprouting takes about three to four weeks.
Transplant the presprouted slips into a specialized bed where they can be allowed to grow out. Bury the slips under two to three inches of evenly moist, but not wet, soil, and maintain a soil temperature of 65 degrees. It may help to cover the bed with black plastic to hold in the heat. Poke holes above the slips to allow for vine growth and ventilation. Slips are ready to transplant into the field when they have six to 10 leaves.
After the threat of the last frost is gone, cut the slips about one inch above the soil surface with a sterile knife. Plant the slips in eight-inch-high rows about eight to 15 inches apart. Space the rows approximately three and a half to four feet apart. For large scale plantings, mechanical planters are often used.