Sweet Potatoes for the Home Garden: Your First Crop From Slip to Storage

Sweet potatoes are one of the most rewarding warm-season crops for a home garden. They produce heavy yields from very little effort once they get going, store through the winter without a freezer, and taste nothing like the rubbery stuff in the produce aisle.

There is one thing most beginners get wrong right away: sweet potatoes are not potatoes. They belong to the morning glory family, they grow from vines instead of tubers, and they need a completely different approach to planting and care. If you treat them like regular potatoes, they will not do well.

This guide walks you through growing your first sweet potato crop from start to finish, including how to grow your own slips from a grocery store root, plant them out, care for the vines through summer, harvest before frost, and cure them for winter storage.

What You Need to Know Before You Start

Sweet potatoes (Ipomoea batatas) are tender warm-season annuals. They do not tolerate cold at all. Frost will injure the foliage, and soil below 60 degrees will keep them from growing. You need a long, warm growing season with at least 85 to 120 frost-free days depending on the variety.

Zone 7a gardeners in the Tennessee area can grow sweet potatoes successfully. The trick is giving them the warm start they need and getting them out of the ground before the first fall frost hits.

Sweet potatoes prefer light, sandy soil but will grow in heavier soils if you amend them with compost. They need full sun, ideally 8 to 10 hours of direct light per day. They are medium feeders, so if your soil is decent, a layer of compost worked in before planting is usually enough.

How to Grow Slips From a Store-Bought Sweet Potato

Sweet potatoes are planted as slips, which are sprouted shoots pulled from a larger root. You do not plant seed, and you do not plant the tuber itself directly in the garden. This is the step most beginners skip, so let me be clear: you need slips.

The good news is you can grow your own slips at home from a single store-bought sweet potato. It takes about six weeks.

Here is how:

1. Pick a firm, healthy sweet potato from the grocery store. Wash it well to remove any anti-sprouting chemicals applied during storage.

2. Cut the potato in half lengthwise so you have two rooting surfaces.

3. Take a clear plastic container or a nursery flat and add 1 to 2 inches of coarse sand or a soilless potting mix on the bottom.

4. Place each potato half cut-side-down in the container, cut surface touching the soil.

5. Cover with another 2 inches of sand or potting mix.

6. Keep the roots moist, warm (75 to 85 degrees is ideal), and covered loosely with plastic wrap. Place them near a warm window or on a heat mat if you have one.

7. After about two to three weeks, you should see green shoots pushing up from the cut surface. Remove the plastic wrap and move the container under grow lights or a very bright south-facing window. Run the lights 14 to 16 hours per day using a timer.

8. Once the slips are about 6 to 8 inches long with a few leaves, pull them gently from the parent root. Each slip will come up with some root attached. If not, you can take a cutting and root it in a jar of water for a few days before planting.

9. Hardened-off slips are ready to go into the garden after the danger of frost has passed and the soil has warmed to at least 65 degrees. In Zone 7a, that is usually mid-to-late May.

You can also buy slips from garden centers or online seed catalogs if you prefer. Growing your own is cheap, gives you more plants to work with, and is satisfying to watch happen.

Planting Out Your Slips

Plant sweet potato slips after the soil has fully warmed. In Zone 7a, aim for mid-May to early June. Planting too early in cold soil is one of the most common mistakes, and it will slow your crop down by weeks.

The best way to plant sweet potatoes is in ridges or mounds. Ridge planting helps the soil warm faster in spring, improves drainage, gives the roots room to expand, and makes harvesting much easier in the fall.

To make a ridge, pile garden soil into a low mound about 4 to 6 inches high and 12 to 14 inches wide. Space rows 40 inches apart and place slips 12 inches apart along each row.

Plant each slip by burying 3 to 4 inches of the stem in the soil. If a slip is very long, you can lay it diagonally in the planting hole and cover more of the stem. Sweet potatoes will root along the buried portion of the stem, which gives you more plants per slip.

Water well after planting. The first 50 to 60 days are the most critical period for moisture. Keep the soil evenly wet but not saturated. Excessive water can cause root rot and splitting of the storage roots.

After about two months, the vines will have established enough that they tolerate dry periods on their own. That is when you can relax on watering unless you get a serious drought.

Care During the Growing Season

Sweet potatoes are not high maintenance. Once the vines get going, they take care of most of their own weed problem by shading the ground.

Watering: Keep the soil evenly moist during the first two months. After that, water during dry spells but do not overwater. Sweet potatoes are sensitive to too much water once they start forming roots.

Weeding: Pull weeds by hand or with a hoe until the vines start to grow. Once the foliage covers the ground, weeding becomes minimal. If you have a weedy patch, a layer of straw mulch between the plants helps.

Feeding: If you added compost at planting time, you likely do not need fertilizer. On sandy soils, a side-dressing of nitrogen once during the season can help the vines grow. Too much nitrogen, though, will give you lush vines and few roots, so hold back if your soil is already rich.

The edible greens: Sweet potato foliage is completely edible and very nutritious. The young leaves and shoots taste similar to spinach or amaranth and can be eaten raw in salads or cooked like any leafy green. Many gardeners snip a handful of greens for salads every week without hurting the crop at all. It is an overlooked bonus of growing sweet potatoes.

Choosing Varieties for Zone 7a

Not all sweet potato varieties are the same. The ones available in US grocery stores are often the moist-fleshed types derived from Porto Rico, which are sometimes called yams at the market. These include varieties like Georgia Jet, Centennial, and Vardaman.

Georgia Jet matures in about 95 days and is one of the most popular choices for shorter growing seasons. It produces medium to large roots with orange flesh and good flavor.

Centennial matures in about 115 days and produces larger roots with a richer, sweeter flavor. It needs a longer season, so it works better if you start your slips early or have a warm southern exposure.

Japanese and Korean varieties are becoming more popular because they have drier, fluffier flesh, store better, and have unique colors ranging from deep purple to golden yellow. They tend to be more tender than American types, so they are worth trying if you live in a particularly warm part of Zone 7a.

For a first-timer in the Tennessee area, Georgia Jet is a safe and reliable choice.

Harvesting Your Sweet Potatoes

Sweet potatoes typically mature 85 to 120 days after planting, depending on the variety. Start checking roots around day 80 to 85 because they do not stop growing once mature, and oversized roots can start to split.

Harvest before the first frost. If frost hits the vines and you do not dig the roots, decay from the dead foliage can move into the tubers. If frost is in the forecast and you cannot dig right away, cut away the vines and pile loose soil over the rows to insulate the roots. Soil temperatures below 50 degrees cause chilling injury.

To harvest:

1. Cut the vines off near the ground.

2. Use a garden fork or spade to loosen the soil around the plants, then gently lift the roots out.

3. Handle the roots carefully. Do not rub the skin, cut them, or wash them before storing. Any damage during harvest will shorten their storage life.

4. Shake off excess soil gently. Let them dry in a shady, well-ventilated spot for a few hours before curing.

Curing and Storing for Winter

Curing is the most important step for sweet potato storage, and it is also the step most home gardeners skip. Curing heals minor cuts and bruises on the skin and converts starch to sugar, which improves flavor and extends storage life.

Home curing does not require a commercial curing room. Here is what works:

1. After harvesting, place the roots in a single layer in a warm, humid spot. A screened porch, a spare bedroom, or a corner of the garage works.

2. Keep the temperature between 85 and 90 degrees with high humidity (80 to 90 percent) for 10 days. A bathroom with the shower running nearby or a covered bin with a damp towel inside can create the humidity. A heat mat under the bin helps with temperature.

3. After the 10-day curing period, move the roots to a cool, dark storage place at 55 to 60 degrees with 85 to 90 percent humidity. A root cellar, an unheated basement, or a cool corner of a garage works well.

4. Check stored roots every few weeks and remove any that show signs of rot. Properly cured and stored sweet potatoes will keep for 6 to 10 months.

If you cannot maintain high humidity for curing, a room-temperature spot with good air circulation will still work. The roots will not store as long and may not be as sweet, but they will be perfectly fine to eat for a few months and are worth curing if you can manage it.

Why Sweet Potatoes Deserve a Spot in Your Garden

Sweet potatoes are easy to grow from a grocery store root. They produce a lot from a small patch of garden. The vines shade out weeds on their own. The greens are edible. And a well-cured crop can feed your family through the winter with almost no effort. The best part is that you only need one or two roots to start with, and you will have plenty of plants by harvest time.

They are also one of the best crops for sharing on CommunityTable. If you grow sweet potatoes in a home garden, you will almost certainly produce more than you can eat. That surplus is exactly what this site is built for.

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— C. Steward 🍠