Starting Tips for Your Sweet Potato Slips
Slips travel dormant and may arrive discolored or wilted, with dry or dead leaves. Don't worry; they grow strongly once they're established.
Sweet potatoes originated in the American tropics but are now a major crop in many climates worldwide. They're extremely sensitive to frost, yet they can do well from slips in cooler regions if a few key needs are met.
Spring is the season for planting sweet potato slips , the shoots sprouted from stored sweet potato roots. If you've never grown them from slips, these illustrated steps will help your crop get off to a strong start. We cover how to keep slips healthy until planting, then bed prep, planting, harvest, curing and storage. Photos from trial plantings in Zone 5b show what to expect and how to set up for the best possible fall harvest.
Arrival & Pre-planting Care
Usually you'd plant live plants in their permanent spot right away, but with sweet potatoes it's essential to wait until soil reaches 60–65°F/16–18°C.
If you can't plant immediately, here's how to keep your slips healthy until you can.
Open the box as soon as it arrives. Packing and shipping are hard on live plants, and slips can look rough: like bare sticks, with leaves that are pale, limp, dried or dead, or with no leaves at all. That usually isn't a problem, since plant tissue is often much tougher than it looks.
Slips can vary a lot in size and appearance, but they'll all grow given good conditions.
Expect differences in length, thickness and the amount of fine white roots on each slip. That's normal, within a variety and between varieties. Some slips have no fine roots, some have plenty, and some are just pushing new bright white roots from the nodes. Having no roots won't hurt yield or survival.
Planted in good conditions, they'll all grow. Large commercial sweet potato growers often prefer bare-root slips, since bare tissue means fewer variables, a cleaner process and no soil carried from one farm to another.
Holding Your Slips for a Day or Two
If planting has to wait, wrap the root ends in damp paper towels while keeping leaves and stems above the root nodes dry. Stand them upright at room temperature, away from direct sun and wind.
Keep slips out of direct sun and stand them upright; if you'll plant within a day or so, a glass or jar works well for each bundle.
Soak the root ends in water for only an hour a day; longer can cause rot.
As tropical plants, sweet potato slips suffer when kept below 60°F/16°C. Room temperature, roughly 70°F/21°C, is best.
Holding Your Slips for More Than a Couple Days
For holding slips more than a couple of days, follow these steps.
Carefully remove the peat packing and loosen the slips.
Take the bundle out of the box, gently separate the roots, and discard any peat moss wrapped around them for shipping.
Set the slips around the edge of a clean pot of potting mix.
Fill a clean pot halfway with potting mix or another sterile medium, space the slips loosely around the edge, and fill to the top with more mix.
Water gently and add mix if needed to cover the roots.
Water to settle the roots into the mix, adding more if necessary. Make sure any fine roots are completely covered.
Keep the pots at room temperature out of direct sun; a spot under a greenhouse bench works well.
If you're holding several varieties, keep them apart and label each pot.
Keep the mix moist. Within a day or two the slips will perk up with bright, healthy leaves, and by planting day they'll have recovered and look great.
Site Selection & Bed Preparation
Loose, well-drained soil with good crumb structure for sweet potatoes.
Matching a crop to the right soil is key to success in the field. Sweet potatoes do best in well-drained sandy loam at about pH 6.5. They don't need high fertility, and loose, sandy soil helps produce evenly shaped roots.
Just as important, this tropical crop needs warm soil. Wait until soil reaches 60–70°F/16–21°C before planting. Most varieties need 90–120 frost-free days. Cold or soggy soil can harm young plants and vines and make slips rot.
In northern trials, laying black plastic mulch down the full length of the bed is an affordable way to warm soil and block weeds. For even more soil warming plus weed control, try solar mulch.
Lay a drip line under the mulch so you can drip irrigation later in the season if needed.
Black or solar mulch can go down to warm soil and smother weeds. Measure so plants are evenly spaced, and punch planting holes through the mulch with a dibble.
For a big planting, a tractor-drawn transplanter can save a lot of time.
Growing in Raised Beds
Raised beds, ideally 6–8" high, suit sweet potatoes well, helping you get the right soil, warmer temperatures and better drainage. Use the same spacing and watering guidelines as for field plantings.
Spacing Sweet Potato Slips
Setting out sweet potato trial plots.
Space slips 10–18" apart in rows 24–60" apart; wider spacing gives bigger roots. One Zone 5b trial planting used 12" between plants and 24" between rows, with two rows per bed and beds 6' apart on center.
Some studies have looked at how in-row spacing and other factors affect sweet potato yield. Your local extension office can also recommend practices suited to your region.
Planting Sweet Potatoes
Once the stakes are set and mulch holes punched, you're ready to plant.
Ease slips out of their pots carefully; their roots will already be developing well.
If you potted up your slips to hold them, take them out of the pot as you would any transplant, then gently separate them. Even after a short holding time, their roots will have grown noticeably.
If hot, dry or windy weather is forecast for the first 3–5 days after planting, consider stripping all leaves off the slips before planting to help them hold moisture.
Next, make a hole deep enough for each slip, one at a time, since lengths vary. Plant slips at an angle or straight down, with 2–4 nodes (growing points) buried 3–4" deep.
If a slip has lots of fine roots, try to get them all below ground. A plain wooden dibble makes this easy.
Judge each slip's length and root spread, push the dibble into the soil, and twist it to widen the hole. That gives you a hole of about the right size.
Close-up of nodes: one on a slip with fine roots, the other on a slip with leaves. Either way, getting at least 2 nodes below ground helps maximize yield.
Put one slip in each hole with at least 4–6" of the root end buried. If a slip is too long for the hole, trim a little off the bottom.
Since the slip's top growing point may be missing, it isn't always obvious which end is the root end. The root end is usually thicker and has nodes that root first, and it points away from the direction any leaf stalks are growing.
With the slip in place, gently push soil back into the hole.
Water well right after planting.
Newly planted slips may droop, since transplanting is a shock, but they'll recover as temperatures warm. A layer of row cover provides a protective, warming blanket.
Slips may look limp or wilted after all that handling. Any plant can suffer transplant shock, and heat and wind, even a light breeze, add stress, both physically and by speeding water loss. Keep the bed watered and give plants time to settle in.
The original leaves often wither, but new ones will appear. In cool northern climates it can take up to a month for plants to really start growing, especially in cool, cloudy weather. If you're worried and see no new growth, gently dig around a slip's crown and look for new roots, which will show how the plant is doing well before the leaves do.
Irrigation
Keep the bed moist before and during planting.
Water thoroughly around the stems right after planting and regularly afterward until plants are established, which can take a week or more. Slips dry out fast, especially in sun, wind or dry air.
Stop watering about 3 weeks before harvest to help prevent the roots from cracking.
Row Cover: An Added Layer of Protection
In the north, you can use row cover for the first few weeks after planting and again in fall before harvest to keep plants warmer and lengthen the season. It's usually optional, though, and the Zone 5b trials pictured here were grown without it.
Harvest, Curing & Storage
Dig the roots in fall before a hard frost. If the vines get frosted, harvest right away, since frost damage moves down from the leaves and stems into the roots. Cut back the vines by hand or with a flail mower, then dig by hand with a spading fork or by machine with a bed lifter. Dig and handle gently to avoid skinning the roots. Heavy or dry soil makes damage more likely, and later varieties often have thinner skins that scuff more easily than early ones.
Cure sweet potatoes before storage to toughen the skin and improve flavor. Brush off loose soil and cure them somewhere warm (about 85°F/29°C), dark and well ventilated, at 85–90% relative humidity, for about 5–7 days. Then store them in a dark place at about 55–60°F/13–16°C and handle them as little as possible. Don't let storage temperatures fall below 55°F/13°C, which can cause chilling injury. For the best sweetness, let roots rest another 3–4 weeks after curing before eating. Well-handled roots can keep for 6 months or longer.
Pests: Critters Love Sweet Potatoes
Sweet potato trial planting in mid-July.
Sweet potato leaves are rich in protein, and deer love the leaves and vines. Rabbits like them too and will nip shoots off cleanly. Without a fence, row cover can keep them from feeding. Voles are fond of tender young shoots and, left unchecked, can destroy a whole planting quickly. Keep garden edges trimmed and mowed to discourage them, or put up ¼" or finer mesh fencing around the garden. Plantskydd, a repellent available in granular and other forms, repellent is approved for organic production and helps deter deer, rabbits, mice and voles.
Sweet Potatoes vs. Yams
Bessey's cactus
"I yam what I yam…"
All sorts of plants around the world get called yams, the sweet potato most of all, but the two crops belong to very different plant families. Both make starchy storage organs that fill similar roles in people's diets, yet true yams are monocots, closer kin to grasses and bulb plants than to sweet potatoes, which are dicots.
A branching, tree-shaped diagram called a cladogram (from the Greek klados, meaning slip, shoot, or arm) can show evolutionary relationships like this. When botanists could only compare plants by their structure, Charles Bessey (1845–1915) developed and drew a classification scheme that became known as Bessey's cactus. In it, the true yam family sits near the base of the lower-left branch among the monocots, while the sweet potato family sits at the very top of the central dicot branch.
The plant family tree has been rearranged a great deal since Bessey's time, as scientists now use DNA and other evidence to work out how plants are related. Those findings can help breeders develop varieties that are more nutritious or better suited to tough and varied environments.
Whatever you call them and however you slice them, give sweet potatoes a try and see how they do in your garden.
Learn More
Growing Resources
- Sweet Potatoes • Key Growing Information
- Growing sweet potatoes (tech sheet, PDF)
- Handling and storing storage crops after harvest (article)
- Sweet potatoes from slip to storage (webinar notes)
References & Further Reading
- Growing Sweetpotatoes in New Hampshire • University of New Hampshire Cooperative Extension.
- Ipomoea batatas (L.) Lam. • Purdue University Center for New Crops & Plants Products.
- Optimizing Sweetpotato Production. • SUMMARY: ScienceDaily.
- Optimizing Sweetpotato Production for Fresh and Processing Markets through Plant Spacing and Planting-harvest Time. • FULL REFERENCE: HortTechnology.
- The Phylogenetic Taxonomy of Flowering Plants. • Annals of the Missouri Botanical Garden.
- The Sweetpotato: An up-to-date publication with emphasis on propagation technologies, pests and diseases, curing and storage. • Springer Netherlands.
- Taxonomy of Flowering Plants. • W. H. Freeman & Co.
