How to grow sweet potatoes from slips to harvest

To grow sweet potatoes, start with slips, which are leafy sprouts grown from a sweet potato root. Plant them after the last frost, once the soil has warmed to 65°F (18°C), 4 to 5 inches deep and about 12 inches apart in loose, well-drained soil. Keep them watered for the first two months, then ease off. Most varieties are ready 90 to 120 days after planting. Dig them before frost, cure them somewhere warm and humid for a week or so, and store them at 55°F to 60°F (13°C to 16°C).

Growing sweet potatoes in your garden

Short growing season? Sweet potatoes need a long, warm, frost-free season, so start slips indoors early and choose a fast variety. University of Illinois Extension notes that bush varieties with shorter vines work where space is tight. If your soil is heavy clay, grow them in a raised bed or grow bag.

Sweet potatoes need warm weather. University of Maryland Extension says frost injures the top growth, and that the crop matures 85 to 120 days after planting, depending on the variety.

Start with a slip

Unlike most veggies you can easily grow at home, sweet potatoes don’t start from seed. Instead, they start from slips, which are leafy shoots that sprout from a sweet potato root.

As we mentioned earlier, you can mail order pre-grown slips if you want to cut down on your time, effort, and trial-and-error. However, trying to nurture your own slips can be a fun and rewarding project for the whole family!

To get started, you’ll need a bag of fresh organic sweet potatoes or some seed sweet potatoes. Cut the sweet potatoes in half, or if they’re very large, they can be divided up into even more pieces. Just be sure to leave a few cubic inches of potato so the baby plant has lots of stored energy available to it.

Next, take a cup or mason jar and fill it with water. Insert four or five toothpicks around the perimeter of your sweet potato halves, about halfway between the cut side and the top. You want to submerge the cut side of your sweet potato pieces in water, and the toothpicks rest on the rim of your cup or jar to keep the top end nice and dry.

Place your prepared sweet potato halves in a warm place. This may be a sunny windowsill or on top of a radiator, depending on your climate. Make sure that you’re changing the water every day, or more frequently if you notice that the water is getting cloudy before 24 hours is up! 

Separating and rooting your slips

After about two weeks, you should get some nice leafy sprouts coming out of the top of your sweet potato and roots growing into the water. Those leafy sprouts are your slips, and it’s time to separate them from their sweet potato mama!

Gently twist the sprouts away from the base of the potato, selecting only those that look healthy. Then, place them in a small container of water so that the bottoms are submerged in water while the tops remain dry. Leave this in a warm environment that gets a good amount of light and change the water daily.

Within a few days, roots should appear. Once again, select the strongest slips with the healthiest-looking roots. Discard any slips that look wilted or diseased. If your slips fail, you can buy slips instead. Mississippi State University Extension says a good slip is firm, green, and 8 to 12 inches long.

Get your soil ready for planting

Sweet potatoes need loose soil so the roots can expand. Sweet potatoes, like regular potatoes, grow very well in grow bags (and there’s less digging too!).

University of Maryland Extension says sweet potatoes grow best in light, sandy soils but also do well in heavier clay soils amended with organic matter. Mississippi State Extension says they grow best at a soil pH of 5.5 to 6.5. A high-quality potting mix works in containers.

Good drainage matters too. Maryland Extension warns that keeping the soil saturated can cause root rot and splitting.

Planting sweet potato slips

Once your soil is prepared and your slips are showing nice, strong roots, it’s time to start planting! 

Plant slips 4 to 5 inches deep and 9 to 15 inches apart, according to Mississippi State Extension. Maryland Extension suggests 12 inches between plants and 40 inches between rows, since the vines spread.

Place one slip in each hole so that the bottom half is underground and the new leaves are exposed. When you’re filling in the space around the slip and tamping down the dirt, do so gently. Slips are fragile, and you don’t want them to bruise!

Timing depends on your climate. According to the Almanac, sweet potatoes need 3 to 4 months of warmth to produce good roots. Maryland Extension says to plant slips once the soil has warmed to 65°F (18°C).

Taking care of your sweet potato plants

Water slips right after planting so they can root, as Mississippi State Extension recommends.

Keep watering through the early weeks, since University of Maryland Extension notes that sweet potatoes are sensitive to drought for the first 50 to 60 days after planting. After that, water deeply during dry spells. Illinois Extension advises stopping watering 3 to 4 weeks before harvest, since heavy late water can split the roots.

Harvesting sweet potatoes

Mississippi State Extension says most varieties mature 90 to 120 days after planting. Maryland Extension suggests checking root size after 80 to 85 days, since roots keep growing and can split when they get too big. Harvest before frost, or right after a light frost, and dig gently with a garden fork a good distance from the crown to avoid cutting the roots.

If frost hits the vines, cut them off and dig the roots right away. Illinois Extension warns that decay can spread from frosted vines to the roots.

Curing and storing sweet potatoes

Curing heals small cuts and turns starches to sugars, so sweet potatoes taste sweeter and keep longer. Iowa State University Extension recommends curing for about a week at 80°F to 85°F (27°C to 29°C) with 90 to 95 percent humidity. At home, Maryland Extension suggests a covered porch or garage for a week or so, protected from rain and animals.

After curing, store them at 55°F to 60°F (13°C to 16°C). Iowa State says properly cured and stored sweet potatoes keep 4 to 6 months. Below 55°F they can develop off-flavors, and above 60°F they may sprout.

Sweet potato growing FAQ

How long do sweet potatoes take to grow?

Most varieties mature 90 to 120 days after planting slips, according to Mississippi State Extension.

When should you plant sweet potato slips?

After the danger of frost has passed and the soil has warmed to 65°F (18°C), per University of Maryland Extension.

How far apart should you plant sweet potatoes?

Plant slips 9 to 15 inches apart, 4 to 5 inches deep. Allow about 40 inches between rows for the vines.

Do sweet potatoes need to be cured?

Curing is worth it. It heals small wounds and converts starches to sugars. Maryland Extension notes that roots usually still store if you skip it, but cured roots taste better and last longer.