Sweet potatoes are grown from slips, or sprouts, that grow from mature potatoes.
The main difference between sweet potato slips and plants is timing. Sweet potatoes are propagated using sprouts --- or slips --- that grow out of existing sweet potatoes. When the slips are a few inches long, gardeners snap them off their host potatoes and plant them in the ground. The transplanted slips then grow into mature sweet potato plants. You can find sweet potato slips at garden centers, but growing your own is fairly simple.
Starting Slips in Water
Starting sweet potato slips in water is easy --- even for the occasional gardener. Place one-third of the sweet potato into water, either on end or on its side. Watch for sprouts to begin growing out of the top of the potato. Once they grow 6 to 8 inches long, these sprouts --- or slips --- are ready to be snapped off and transplanted into the outdoor garden.
Starting Slips in a Hotbed
Growing sweet potato slips in a hotbed is an efficient method for the gardener who wants to plant a fairly large crop of potatoes. The University of Illinois Extension recommends placing several sweet potatoes about an inch apart in a hotbed and covering them with about 2 inches of sand or soil. When shoots begin to sprout out of the sand or soil, add another inch of sand. Keep the soil moist, but not overly wet. The soil temperature should hover between 70 and 80 degrees Fahrenheit. The slips are ready to snap off and transplant into the outdoor garden when they are 6 to 8 inches tall.
Planting & Care
Sweet potatoes can take up to 150 days to grow from transplant slips into mature vegetables. So it's important to plant sweet potato slips in the spring as soon as the threat of frost has passed to allow the plants enough time to mature before fall harvest. Space the plants 12 to 18 inches apart, leaving about 3 to 4 feet between plant rows to allow for spreading vines. You can encourage early season growth by using black plastic mulch to warm up the soil. Sweet potato beds need little weeding as the spreading vines choke out the weeds. Water only during extended dry periods; stop watering three to four weeks prior to harvest.
Harvest
Harvest sweet potatoes around the first fall frost. If you want larger potatoes, you can "rob" early roots in the late summer. This involves digging around the root and removing small developing roots that are sprouting out of the plant. Harvest potatoes using a spading fork or a small shovel. Dig carefully around the plants, removing soil until you can see the roots. Dig under the roots and remove the potatoes. Let them dry on the ground for two to three hours. If possible, place them in a warm, humid room --- 85 degrees Fahrenheit and 85 percent humidity --- to cure for about two weeks. Move your cured sweet potatoes to a cool (approximately 50 degrees F) place. Eat the potatoes as soon as possible after harvest for best quality.
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