Sweet potatoes are a delicious and highly nutritious vegetable that can be easily grown in the home garden. You can be growing sweet potatoes in your own garden this summer if you get started in late winter to early spring.
Sweet potatoes are sometimes referred to as yams, but in fact, yams and sweet potatoes are two different species and are unrelated. The sweet potato plant is actually a perennial that is commonly grown as an annual. The Latin name for sweet potatoes is Ipomoea batatas and they are in the morning glory family. When you are growing sweet potatoes you may notice small blossoms similar to morning glory blossoms hidden amongst the vines.
When growing sweet potatoes you do not begin by planting seeds. Like white or red potatoes, sweet potatoes are grown from seed potatoes, usually, some that are left over from the previous year’s crop. But when growing sweet potatoes, there is an extra step involved, because sweet potato plants are grown from slips. Slips are a small section of sweet potato vine that has grown from a sweet potato tuber.
Sweet potato slips can be purchased from some seed catalogs, or you can grow your own slips. All you need is a whole sweet potato, some toothpicks, a jar or glass of water, and some small pots with potting soil.
Sweet potato plants do not tolerate frost at all, and they cannot be planted out until about until the soil has warmed to at least 65 degrees, a week or two after all danger of frost has passed. Begin making slips for growing sweet potatoes about 8-10 weeks before the last frost date in your area.
Begin by sticking three or four toothpicks around the circumference of the sweet potato about halfway down its length. Place the sweet potato into the jar or glass and fill the container with water, leaving about half of the sweet potato above the water line and propped up with the toothpicks. Soon the sweet potato will start to grow roots in the water, and not long after that sprouts will begin to appear on the potato above the water. The sprouts will be your slips for growing sweet potatoes.
Once the slips are 4-5 inches long, they can be cut from the sweet potato. Leave about a quarter-inch stub of the slip on the tuber and it will produce another slip for you. One sweet potato can produce more than a dozen slips.
Once a slip has been cut from the parent sweet potato, it can be planted in small pots of soil and allowed to root. The slips can also be planted directly in the garden, but if they are allowed to develop a root system before they are planted out, you will achieve a larger crop of tasty tubers.
Plant slips 3-4 inches deep, with 3 or 4 nodes beneath the soil. A node is the bump on the slip where a leaf attaches to the stem. Growing sweet potatoes in well-drained, sandy loam soils is recommended for the best crop and an easier harvest. If your soil is heavy, consider growing sweet potatoes in raised beds 6-9 inches high, or in bottomless barrels or stacks of tires.
Since sweet potatoes love heat, it makes sense to grow the plants inside two or three old tires stacked one atop another. Fill the stack with soil and plant one to three slips per stack. The black rubber tires will absorb heat and that heat will make your sweet potato plants very happy. Come harvest time, just pull off the top tire from the stack to reveal your sweet potato crop. Sweet potatoes will grow most vigorously in temperatures between 70 and 85 degrees Fahrenheit, so the stacked-tire method is ideal for cooler, northern growing zones.
Sweet potato plants, like their relatives the morning glories, grow long, lush vines. The vines or runners will take root where they touch the soil. Do not allow the runners to take root as this will reduce the harvest. Growing sweet potatoes in bottomless barrels or stacked tires help prevent the runners from taking root.
Plant sweet potato slips at least 12-18 inches apart in rows 3-4 feet apart. The more room the plants have to spread out, the faster the tubers will grow. A soil pH of 5.0 to 6.5 is ideal for growing sweet potatoes.
Sweet potato plants may need a dose of phosphorus and potassium fertilizer, but be careful to not apply too much nitrogen to the soil. Excess nitrogen will encourage the plants to grow beautiful, lush vines but very few sweet potatoes. Avoid applying high-nitrogen manure to the sweet potato-growing bed.
Depending on the variety, sweet potatoes are ready to be harvested anywhere from 95 to 150 days after the slips are transplanted to the garden. Sweet potato plants cannot tolerate frost and the crop should be harvested before the first frost. A light frost will kill the vines but will not harm the tubers beneath the soil. When the tubers are ready to be harvested the foliage generally begins to yellow slightly. Two or three days before harvesting, cut the vines to ground level. This will help to toughen the skins on the sweet potatoes.
Handle the sweet potatoes carefully as they are harvested to avoid bruising the tubers or tearing their skins. Do not wash the sweet potatoes.
Before they can be eaten or stored, freshly dug sweet potatoes must be cured. Curing increases their sugar content and allows the flesh to become more orange. An uncured sweet potato has very little flavor and will be disappointing.
To cure sweet potatoes, place the freshly dug tubers in a warm, humid environment for 4-6 days. A temperature of 85 degrees and a humidity level of 90 percent is ideal for curing sweet potatoes. Once cured, the sweet potatoes can be placed in boxes or bins and kept at a temperature of 55-60 degrees. A root cellar or unheated basement or garage would be appropriate for long-term storage. Sweet potatoes should not be stored in the refrigerator, as the humidity is too low.
Growing sweet potatoes is a fun project for any vegetable gardener. Besides providing nutritious food for your table, the growing sweet potato vines are also quite lovely in the garden.