How to Plant and Harvest Sweet Potatoes
The arrival of cool fall weather means it’s time to harvest sweet potatoes, delicious veggies packed with fiber, vitamin C, beta-carotene and other nutrients.
Northern gardeners should bring in their sweet potatoes before the first frost arrives, while gardeners in other parts of the country will know their potatoes are ready when the vines start to yellow.
To harvest, wait for a day when the soil is dry, and use a spading fork to loosen the ground in a wide circle around each plant. (If you use a shovel, be careful not to chop into any of the potatoes. Even minor damage can lead to spoilage.) Use your hands to pull them out of the ground, shaking off the dirt as you free them.
Leave the newly dug potatoes to dry in the sun and fresh air for a few hours. Then store them in a box lined with newspaper, and keep them in a spot that gets good air circulation for a couple of weeks. The ideal temperature for letting them continue to dry, or cure, is 85 to 90 degrees F.
Next, move the sweet potatoes to a root cellar, if you have one, or a location where the temperatures are cooler, between 55 and 60 degrees F. An ideal humidity would be 75 to 80 percent. Check the sweet potatoes regularly, and discard any that show signs of spoilage. Properly cured, they should keep for several months.
When you’re ready to plant next spring, remember that sweet potatoes are tropical plants that thrive in warm climates. Wait until a month after the last spring frost to start them. Northern gardeners may want to cover their soil with black plastic or black garden fabric for a few weeks before planting; the material will absorb heat from the sun and help warm the soil faster.
Sweet potatoes are started from slips, which are root sprouts. Choose slips that are certified “disease-free,” to avoid introducing fungal diseases like scurf or pests like sweet potato weevils. Both are very hard to eliminate once they get started.
Plant the slips up to their top leaves, about 6” deep and 12” apart. Give them a spot in full sun with well-drained soil, and mix lots of good compost into the bed. If your soil is heavy clay, try raised beds amended with compost and sand. You can also grow sweet potatoes in large containers, letting the vines run or trellising them.
Weed often, and water deeply and regularly if rain is absent. Err on the side of under watering, though, as sweet potatoes can handle some dry periods. Let the vines start running for a couple of weeks before you apply a layer of mulch. Feed the plants with a balanced organic or timed-release fertilizer containing potassium.
Varieties to try in your garden:
- Sweet potato ‘Beauregard’ – a sweet, moist, popular variety with a deep orange color. Matures in 90 days. Well adapted to most areas; recommended for Northern gardens.
- Sweet potato ‘Vardaman’ – A compact, bush-type recommended for gardeners with limited space. The skins are gold, and the flesh is a rich orange. Easy to grow and high-yielding.