How to Grow and Harvest Sweet Potatoes
A sweet potato is, as its name suggests, a sweet tuberous root vegetable that grows prolifically underground. "In many cultures, the young shoots and leaves are also eaten as greens," explains Greg Peterson, founder of The Urban Farm. There are dozens of sweet potato varieties—and they are not to be confused with yams, which have bumpy, bark-like skin and starchy, less-sweet flesh—from the popular Beaureguard to the tasty Jewel; they come in all different colors and sizes. Ahead, exactly how to grow and harvest sweet potatoes, so you can enjoy them alongside your favorite fall-time recipes.
Sun and healthy soil are key.
Sweet potatoes can be grown in USDA hardiness zones six and higher, and they will thrive perennially in zones eight and above. "As with other food-growing plants, they require a generous amount of sunlight to actually generate the tuberous edible parts," Peterson explains. "But the single biggest success factor that a gardener can employ is creating healthy soil in their growing beds." Adding nutrient-rich compost will help improve the earth around your home: "With sweet potatoes and other root vegetables, this is particularly important as growing in hard, compacted soil nets roots that are skinny and less abundant."
Water and fertilize mindfully.
Maintain a consistent watering schedule. "Clay soil may need less water than sandy soil," Peterson shares. As for fertilization? Getting nutrients to your sweet potatoes is important, but standard formulas likely won't cut it. "NPK (nitrogen, phosphorus, and potassium) are the macronutrients that are typically found in a bag of fertilizer, but these plants need many more," he adds, noting that both organic and non-organic fertilizers usually contain these three, which will be listed on the packaging. Instead, look for bags labeled 6-5-5 or 8-15-7. "As a general rule, if any of the numbers are larger than 10, the fertilizer is not organic," he flags. Organic is best, says Peterson, for both your plants and your soil. "It is important to note that garden nutrition is multifaceted. Using just one form of fertilizer will likely not be the most effective solution," he explains.
Head to the grocery store to start your own sweet potato patch.
To grow your own, Peterson suggests making a trip to your local grocery store in April and grabbing a few organic sweet potatoes from the produce section. "Organic is important," he shares, "since non-organic sweet potatoes have been sprayed with a chemical herbicide called chlorpropham. This prevents them from budding out."
Help your sweet potato grow slips.
Once you return home, all that's left to do is wait: Set your organic spud on the counter—for the best results, place the sweet potato in water, with the tapered end down—and let it do its thing for about a month, Peterson notes, during which it will produce "slips" or shoots (they should be six inches to a foot long). Next, separate the slips from the potato, leaving the roots attached. If they don't have a root system yet, no problem: Place the slip in water for a week or two to help them develop. Remember to time everything just so: You should plant your slips, their roots included, into the earth about three to four weeks after the last spring frost.
Know when to harvest sweet potatoes.
The best time to harvest sweet potatoes is in the fall, after a three- or four-month-long growing period. "I watch for the tops to start dying back from the cold, which usually happens around the beginning of November," Peterson says. "When it comes to harvesting, I like to leave several roots behind so that they automatically grow the next season." After you've collected your bounty, store these root vegetables in a cool, dry place, like a root cellar, until you are ready to enjoy them.