How to Grow Sweet Potatoes

Sweet potatoes were considered to be a winter holiday treat in my family, until we moved to Tennessee. Now they have become a basic staple. The main reason we learned how to grow sweet potatoes is that regular potatoes don’t store well in this warm climate without sprouting and becoming soft within a few months of harvest. But sweets easily keep until the next year’s harvest.

Grown from Slips

Unlike our Yukon Gold, Yukon Gem, and Purple Majesty potatoes, which grow from small seed potatoes, sweets grow from slips. The slips are started by suspending the bottom half of a potato in water, pointy end down.

I once found some ceramic pots that are ideal for the purpose. I bought 3 and wish I had bought a couple more, as I never saw them again. A suitable alternative is a wide-mouth canning jar.

Initially I suspended the potatoes with toothpicks, three per potato. But toothpicks can get soft and break before the slips are ready. Now I use poultry lacers. They slide in easily, don’t bend or break, and don’t rust, so they may be used from year to year.

Around 6 weeks before the expected last frost we pot the potatoes in water and set them on the windowsill. Sprouts appear about one month later. They are optimum for transplant at 10 to 12 inches, with 5 or 6 leaves. Each potato produces 10 to 20 slips.

Transplanting Slips

After danger of frost has passed, the slips are planted horizontally in long rows, with the stems about 2 inches deep and the terminal buds about 15 inches apart. Only the two terminal leaves remain above ground. We plant ours in blocks, with the rows about 3 feet apart.

Unless they are transplanted during a cloudy spell, the slips do best when they are protected from sun for the first 3 days or so. Covering the soil with mulch, taking care not to damage the slips’ terminal buds, helps keep them moist.

The slips need to be watered often for the first 2 to 3 weeks. After that about 1 inch of water a week is about right.

The vines continue to spread as they grow, setting down new roots to match the vines. Some expert growers recommend cutting vines to a 3-foot radius around each mother plant. We cut only vines that venture outside the bed and into the surrounding path.

We use the delicious tender leaf tips in salads. The rest of the cuttings go to our Nubian dairy goats.

Sweet Potato Varieties

Sweet potatoes come in a wide range of sizes, shapes, colors, textures, and flavors. I wish I could tell you which variety we grow. But, to be honest, I bought some at a market that we liked, so I took a chance and stuck one in a jar of water. That was decades ago. We’ve been growing that variety ever since, starting this year’s slips by setting aside the best few of last year’s sweets.

Sweet potatoes can accumulate viruses like regular potatoes do, and they tend to mutate. So eventually we may need to start over, preferably with certified disease-free potatoes or slips.

The ideal potato to save for growing slips comes from a well producing plant. A starter potato should have a diameter between 1½ and 2½ inches. It should have smooth skin with no damage or sign of disease. Some years the ideal starter sweets can be hard to find if we aren’t super careful to avoid damage during the harvest.

Harvesting Sweets

The potatoes are ready for harvest about 120 days after transplant, but no later than right after the first frost. We stop watering during the last 3 weeks before harvest, as sweets dug from soggy ground may crack after being harvested. This part presents a challenge during rainy weather.

We start the harvest by removing the vines and hauling them to the goat barn. We usually cut only one or two rows at a time, both to avoid overloading the goats and to avoid overloading our backs digging up the bountiful harvest.

The potatoes must be dug up within a few days of vine removal. Each plant produces a cluster of 8 to 12 good-size potatoes, with some smaller renegades surrounding the main group.

For the first 10 days after harvest, the potatoes should be stored, unwashed, out of the sun where the temperature is 80°F to 85°F and the humidity is high. We spread them on cardboard on our covered back porch. After about 10 days the soil has dried enough to be brushed off. Then we move the sweets into crates for storage in our dark, cool pantry.

We enjoy eating them all winter. When winter forage is scarce, we also slice some raw sweets to share with our Nubians. They always do an eager head-bobbing dance when they spy the sweet potato bucket.

Until we came to Tennessee we had no idea how to grow sweet potatoes, and that they may be grown in zones 3 through 11. Nothing in our garden is as easy or cheap to grow for the quantity produced and the amazing nutritional benefits. And some years we are further rewarded with the rare sight of a beautiful sweet potato blossom.