Sweet potatoes can provide big yields of tasty and nutritious roots with relatively little effort. They’re often confused with yams, but sweet potatoes are a different plant altogether. And while commonly a southern crop, short-season varieties can be grown by many northern gardeners.

Sweet potatoes are plants in the morning glory family, and the root portion we eat will continue to grow as long as the plant is alive. They are grown from slips, which are sprouts on sweet potatoes from the previous year’s crop. Slips look a bit like a rooted cutting.

Most sweet potato varieties are vining plants that can take up a lot of space, but there are bush types available that are much better suited to small spaces or containers. Sweet potatoes in vine form can even be trained to climb up a trellis or arbor.

It’s the tasty orange roots that we’re normally after, but the young shoots and leaves of the plant are also edible. Keep the main growing shoot intact and harvest only leaves and shoots from the side stems for a tasty green treat.

Unpacking sweet potato slips

Sweet potato slips purchased online are shipped based on the arrival of planting weather for your location. Southern gardeners will typically see delivery dates in April, while those in the north will receive their slips in late May or even early June.

Your sweet potato slips should be removed from the shipping box immediately. Leaving them in the box can cause issues with mold and rot. It is normal for the young sweet potato plants to look a bit wilted and bruised. Remove them from any wrappings or internal packaging.

If you are unable to immediately plant your sweet potato slips, they will need to be kept moist. Slightly spread them apart, and then wrap the root ends with a wet paper towel. Place them upright in a bucket or jar, and rewet them daily until planting. If you need to hold them for longer than a few days, temporarily plant them as a group in a small pot with some sterile potting mix, keeping them moist. 

Choosing a site for sweet potatoes

Sweet potatoes want to grow, but choosing a proper site will help them along. They need a sunny spot, preferably with 8 or more hours of sunlight per day. Planting them in partial sun locations will result in lower yields. 

Most importantly, sweet potatoes need a site with good drainage. Heavy, wet soils not only restrict the development of the nice-sized storage roots we want, but also increase the risk of root rot. A sandy loam or loam soil is ideal, with a pH of around 6.0-6.5, which handily is the sweet spot for many veggies. 

Planting Sweet Potatoes

Sweet potatoes are warm-weather crops, and the soil needs to be at least 65℉ before planting. Normally, the soil has reached that temperature range three to four weeks after your last spring frost date. 

Sweet potatoes can be planted in raised beds or in raised ridges formed from garden soil. If building ridges to plant them in a traditional garden, build the berms about 8-12 inches high and at least 12 inches wide. The ridges warm faster in spring, have better drainage, and make harvesting easier than digging holes and planting on flat ground. If making more than one ridge, space them about three feet apart.

Plant sweet potato slips about 6 inches deep, with at least 2 nodes below the soil and 2 above. More nodes underground means more sweet potatoes, all else being equal, but you’ll still need nodes above ground for leaves to form. Nodes are where leaves emerge from the stem and typically appear as little bumps. Space slips about 12 inches apart in the row. 

Water sweet potato slips daily for the first week or two until you see new growth, then provide 1 inch of water per week if rainfall is insufficient.

Midseason Care for Sweet Potatoes

Sweet potatoes are easy to care for. A little water and some fertilizer, and they will be on their way.

Sweet potatoes form a vigorous canopy of foliage and often take over the bed, shading out any weeds as they spread. Pull out any weeds that do pop through to prevent them from going to seed. A mulch of shredded leaves or grass clippings (from a non-treated lawn) can reduce early weeding. 

Sweet potatoes are sensitive to dry conditions for the first two months after planting, and will need to be watered if you haven’t received rain. About an inch per week, like the rest of the vegetable garden, is sufficient. You may wish to slow down watering a few weeks before harvest to reduce the likelihood of root splitting, but don’t let them get so dry that they wilt.

Avoid excess nitrogen for sweet potatoes. Similar to a tomato, sweet potatoes given too much nitrogen will have loads of vibrant green foliage, but yields will suffer. The plants get too busy growing above ground, and don’t put as much energy down into the storage roots. Wait 3 weeks after planting before fertilizing for the first time. A low nitrogen product, like a 4-10-5, is better than one with a higher nitrogen content. If fertilizing, feed them once or twice during the earlier part of the season and avoid late-season applications.

Growing Sweet Potatoes in Pots

While sweet potatoes are typically grown in the ground, they do quite well in large containers. The key is selecting a suitably sized pot. These are big plants, and keeping them in a pot that is too small will limit their growth and, consequently, their yields. Porto Rico is an excellent variety for container gardening. Its bushy growth habit will create a lush, overflowing planter but won’t send vines sprawling across your patio or balcony. 

Choose a large container or a grow bag, and use a potting mix with good drainage. If the potting mix you have doesn’t contain perlite, you may wish to add some to help with drainage and aeration. Look for pots larger than five gallons. Grow bags in the 10-gallon range are inexpensive and ideal for a single sweet potato plant, while a 20-gallon bag can support 2-3 plants.

Keep in mind that plants in pots or bags will need more frequent watering and fertilizing than those planted in the ground. You may need to water several times per week.

Harvesting, Curing, and Storing Sweet Potatoes

Sweet potatoes are ready for harvest when the tops begin to die back and turn yellow, generally about 90 or more days after planting. If you aren’t sure, gently move some soil and do a test dig. Sweet potatoes can be harvested as soon as they reach eating size. 

Even if they don’t appear ready yet, harvest them before the first fall frosts, as the vines will die and decay can rapidly move down the dead vines into the roots. If the vines are killed by frost, don’t delay harvest. 

• On harvest day, start by cutting back all the vines to near ground level. Attempting to fight your way through the tangled foliage makes it harder to find all the sweet potatoes. 

• Use a garden fork or spade to loosen the soil and gently lift the roots. Start from farther away than you think the plant might have put down roots and work your way closer to avoid spearing a sweet potato. The sweet potatoes will normally be within the top ten inches of soil.

• Handle the sweet potatoes carefully, as their thin skin is prone to damage.

• Rub excess soil off gently, but don’t wash the roots. Leave the last bit of soil on and proceed to the curing steps.

For sweet potatoes grown in a grow bag or pot, spread a large tarp on the ground and simply tip the pot right over onto the tarp. The roots are easily found, and the tarp makes it easy to collect and reuse the potting mix.

Curing & Storage for Sweet Potatoes

Curing sweet potatoes is important for quality, shelf life, and flavor. The curing process converts starches to sugars, providing a sweeter flavor. Any small wounds on the root can seal over, preventing rot later.

Ideally, sweet potatoes are cured for a week at 80-85℉ and high humidity, around 90%. However, that can be hard to achieve at home. Spread the unwashed roots in a single layer on a tray or table in a sunny, warm location, such as an enclosed porch. They can also be put in plastic bags with a few slits for aeration, and placed in a sunny, warm window where the temperature will be above 80℉.

To store sweet potatoes after curing, keep them in a dark, cool location at about 55-60℉. Avoid refrigerator-type temperatures, as they can cause woody texture and off flavors. With proper storage, sweet potatoes can last six months or more.