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Planting, Growing, and Harvesting Sweet Potatoes
A few sweet potato plants can produce a generous harvest! This nutritious, sweet-tasting root vegetable is heat-tolerant and pest-resistant. Here is everything you need to know about growing sweet potatoes.
Though commonly grown in the South because they require warm weather, northern regions can have success, too. See our advice on which varieties to choose below.
About Sweet Potatoes
The sweet potato is a tropical plant and is actually a member of the Morning Glory family. Compare a sweet potato vine鈥檚 foliage and flowers to those of morning glory, and you鈥檒l see the family resemblance! Despite their name, they are not related to potatoes, which are in the nightshade family. Another difference between sweet potatoes and 鈥渟tandard鈥 potatoes is that the edible portion of the sweet potato is a tuberous root, not a true tuber (which are technically modified plant stems).
This root vegetable has deep-orange flesh and a coppery skin jacket. Sweet potatoes are commonly served cooked in mashed form or roasted whole. They may also be used as pie filling.
This tropical crop needs at least 4 months of warm weather and warm soil, but they are drought- and heat-tolerant and have few pests or diseases. Although traditionally more of a Southern crop, there are many short-season sweet potato varieties today. They will grow in the North (even parts of Canada!) when grown in sandy soil or raised beds mulched with black plastic to keep the soil warm.
Sweet Potato Slips
Note that sweet potatoes are not grown from seed. Instead, they鈥檙e grown from slips, which are sprouts from existing sweet potatoes. Slips are often available at local garden centers and nurseries, from local farmers (such as farmers鈥 markets), or mail-order companies. Or you can start your own (see below).
Before you order slips, please make sure that you have a long enough growing season to grow sweet potatoes. Most varieties will take about 90 to 120 days to mature. See your frost dates and length of growing season. Also, ensure you time your order with your planting dates in mind!
Planting
Choose a sunny spot with well-draining soil. Sweet potatoes aren鈥檛 too picky, but they do prefer soil on the sandier side. They need plenty of air space in the soil for roots to reach down. Consider growing in raised beds if your soil is clay, rocky, or compacted.
Add compost, perlite, and/or coconut coir to the growing area to build fertile, loamy soil down to 8 to 10 inches. Avoid adding animal manure, including pelleted chicken manure; it can result in spindly and/or stained roots. Also, avoid heavy nitrogen fertilizers, which produce lush leaf growth at the expense of the edible roots!
When to Plant Sweet Potatoes
- Plant slips outdoors, 3 to 4 weeks after your last spring frost or once the soil has warmed to at least 65掳F (18掳C). Nighttime temperatures should be at least 55掳F (13掳C). The trick is to plant them early enough to have time to mature fully but not so early that they get killed by a late spring frost.
- Be sure to protect young sweet potatoes from late frosts or cool nights (lower than 55掳F/13掳C), as they are very tender. Cover them with plastic milk jugs or use row covers, removing the covers during the day.
- If you ordered slips from a mail-order source, unpack them right away. Stick the roots in water for a day or so, and they鈥檒l perk up. Plant them as soon as conditions are right.
Credit: Lex20/Getty Images.
How to Grow Your Own Sweet Potato Slips
You can start your own slips instead of buying them, but it鈥檚 more work. Here鈥檚 how:
- About 8 weeks before your last spring frost date, look for unblemished, smooth, organic sweet potatoes at the store or farmers market. Be sure to ask about the variety and check that it鈥檚 one you want to grow.
- Place the whole sweet potatoes in pots or bins that contain at least 3 inches of light, organic, well-draining soil. Leave an inch or two of space between each sweet potato.
- Lightly cover with a few inches of additional soil. Water now and as needed to keep soil damp but not soggy.
- Maintain the soil and the room at 75掳F to 80掳F in sunlight or under artificial lights. Use a heating mat if necessary; sweet potatoes respond well to warm temperatures.
- Soon, slips (shoots) will emerge from the soil.
- After about 6 to 8 weeks, the slips should be between 6 and 12 inches long, with a number of leaves and roots.
- Remove the slips from the sweet potatoes with roots attached. (If no roots have formed on the slip itself, remove the slip and place it in water; roots should appear in 1 to 2 weeks.)
- If it is still too soon to plant outdoors, stand the slips in potting mix or sand and keep them moist until the right planting time (3 to 4 weeks after the last frost).
- Harden off the slips (before planting outdoors) for 1 to 2 weeks by exposing them to filtered sunlight outdoors during the day.
How to Plant Sweet Potatoes
- Create raised mounds 6 to 8 inches tall and about 12 inches wide.
- Plan 3 feet between mounds so there is enough space for vines to run.
- Plant the slips on a warm, overcast day when the soil temperature has reached 60掳F (15掳C).
- Break off the lower leaves, leaving only the top ones.
- Set the slips deep enough to cover the roots and the stem up to the leaves. Sweet potatoes will form on the nodes.
- Water with a high-phosphorus liquid fertilizer, then water generously for 7 to 10 days to make sure that the plants root well.
Growing
- Side-dress the sweet potato plants 3 to 4 weeks after transplanting with 5-10-10 fertilizer. If you have sandy soil, use more.
- Weed the sweet potato beds regularly, starting 2 weeks after planting.
- Avoid deep digging with a hoe or other tool that disturbs the delicate feeder roots.
- Water regularly, especially during mid-summer. Deep watering in hot, dry periods will help to increase yields.
- Do not prune sweet potato vines; they should be vigorous.
- Late in the season, reduce watering to avoid cracking of the sweet鈥檚 skin鈥攁 problem in storage.
Credit: Getty Images.
Growing Sweet Potatoes in Containers
Bush-type sweet potato plants are ideal for container growers. The vines that they produce are short and compact, not sprawling like typical sweets鈥攂ut the roots are full size, not miniatures.
While slips mature, prepare a large container or tub. (A too-small container can result in small, curly sweets or fewer than hoped for.) A 10-gallon container can support two or three sweet potatoes; a 20-gallon one, four to six. A half-barrel container (20 to 25 gallons) is ideal. Place the container where it will receive full sunlight every day. (It will be heavy to move once filled and planted.)
Sweets like moist but not wet soil; the medium must be well-draining and rich; sweets are also heavy feeders. Provide potting mix amended with compost, sand, bonemeal (for potassium), and wood ash (for potash). Minimize nitrogen or risk producing heavily leafy tops and spindly roots. If you purchase a bush variety, soak the roots in water for a few hours before planting.
Plant slips 3 to 4 weeks after the last spring frost, when the soil has warmed to 65掳F and nighttime temperatures are at least 55掳F. Mulch with black plastic before and during the season, if necessary, to capture or retain heat. Set slips 4 inches deep on a bed of compost, then cover up to their bottom leaves. Water with a high-phosphorus liquid fertilizer (5-10-10) for 7 to 10 days to ensure that the plants root well.
Harvesting
- You can start digging up the roots when they are big enough for a meal.
- Harvest when the leaves and ends of the vines have started turning yellow or about 100 days from planting.
- Loosen the soil around each plant (18 inches around, 4 to 6 inches deep) to avoid injuring the roots. Cut away some of the vines.
- Pull up the plant鈥檚 primary crown and dig the roots by hand. Handle the sweet potatoes carefully, as they bruise easily.
- Shake off any excess dirt; do not wash the roots.
- Complete harvesting by the first fall frost.
How to Cure and Store Sweet Potatoes
- Curing sweet potatoes gives them a sweet taste and also allows a second skin to form over scratches and bruises.
- Handle sweet potatoes carefully; they bruise easily.
- To cure, store roots in a warm place (about 80掳F) at high humidity (about 90%) for 10 to 14 days. A table outside in a shady spot works well. Arrange sweet potatoes so that they are not touching.
- After curing, discard bruised sweet potatoes, then wrap each one in newspaper.
- Carefully pack in a wooden box or basket. Store in a root cellar, basement, or the like with a high humidity at 55掳 to 60掳F.
- The roots should last in storage for about 6 months.
Cooking Notes
Relatively low in calories, sweet potatoes are very nutritious, a top source of beta-carotene, and contain some protein, calcium, iron, vitamins A and C, and other minerals. They can be stored longer than winter squash.
To cook, sweet potatoes are easier than pie (or sweet potato pie!).
- They can be scrubbed, poked with a fork in a few places, and baked at 400掳F for 35 minutes to 1 hour, until they give a bit when you squeeze them in your pot-holder鈥損rotected hand.
- In the microwave, a whole sweet potato baked on high should be ready in 4 to 6 minutes. It may still feel firm when done; let it stand for about 5 minutes to soften.
- Sweet potatoes can also be steamed whole (cleaned and unpeeled) for about 40 minutes or until tender or cooked whole (cleaned and unpeeled) in boiling salted water for about 35 minutes. (Boiling reduces the flavor considerably.)
- Immerse cut raw sweet potatoes in water until you’re ready to cook them; they will darken otherwise.
As a general rule, don’t substitute sweet potatoes for regular potatoes in recipes; the two aren’t related. Sweet potatoes don’t hold together the way potatoes do, and their strong flavor can overwhelm a dish meant for a milder potato taste. Sweet potatoes are also not related to yams. But they make a fine substitute for pumpkin, especially in desserts.
Check out our ten best sweet potato recipes!
Catherine Boeckmann
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Yes, get them covered again as soon as possible, then check back in on them when they’re due to be harvested!
We planted our sweet potatoes the 3rd of June, due to the rainy Iowa weather we could not harvest until Oct. 13th. The average size of each potatoe is approx. 6 lbs. and a lot of them are 10 lbs. each. They are way to huge, bit the flavor is good. Would they have been a lot less in size if harvested a month earlier? Thank you.
I bought some sweet potato seeds from Amazon last year but when they arrived there were no instructions as to how to start seeds. Can you help me with instructions as it is time to get going this spring?
We are not familiar with starting sweet potatoes from seed and your purchase was unfortunate. In the same way that white (and blue and red, etc) potatoes are grown from seed potatoes (small spuds grown specifically to be planted for later harvest), most people grow sweet potatoes from small sweets, which are called 鈥渟lips.鈥 We are guessing that it could take a few years for seeds to develop (and maybe you want to try that) and recommend that you purchase slips to insure that you get a harvestable crop. These, like seed (white) potatoes, are set in the soil. See above for more specific growing information.
For curing Sweet Potatoes, remember that 80 degrees with high humidity is the ideal, but not a exact requirement. In order to store them in the cool you need to time your harvest to that time of the year that is cooling off in your region. Otherwise your are trying to cure them in 90-100 degree weather or if too late in the year, 30-50 degree weather. I harvest mine when the weather is starting to change in October (NE Louisiana), when some days are in the low to mid 80s. After you have dug them up, DO NOT wash them. This removes healthy bacteria and opens them up to fungus decay. Let them dry outside under a shed (out of the sun and rain) for several days. This helps get them dry. Then transfer them to a storage room or a room in your house that stays around 80 degrees or fluctuates in the 60-90 degree range (I keep mine in an outside storage room spread out on racks or on the floor). If you mist stack them, try not to stack them more than two deep, as their skin contact slows the drying process and promotes fungus growth. For humidity I keep a couple of five gallon buckets of water with wet towels around the edge of them or hung up above them. Saturate the towels every day. The evaporation will add humidity to the room. The curing process may take ten days or it may take 30 depending on your situation. When the skins are no longer easily scraped off, they are cured. By then the weather will be cooler and I keep them in the same storage room (with NO water or wet towels). My winters here are mild, but the temperature in my storage room varies from 75-30 degrees throughout the winter, and mine store fine for 6-8 months. I have repeated this process for many years. Remember, our ancestors grew and stored these potatoes with very little temperature and humidity control, and they did fine. Regarding the question of having great looking vines but few potatoes, first I would get a good soil test done, but as they were grown in a raised bed, too much Nitrogen may be the problem, as excess N will tend to put more growth into the vines than the roots. Same thing goes for peas. I hope this helps. Happy gardening.
I put potatoes in glass jars supported by tooth picks,when slips get long enough I then break them off and put them in another jar to root.
We have 1/4 acre garden. It's a major amount of work. So we cut corners where we can to save time. I start sweet potatoes in March, 60 days ahead of planting. I pick out tubers from last years harvest, usually medium size, although this is a good way to use small ones that are still good. I stick 3 toothpicks around the sides and suspend the tubers vertically in a jar (like pints) of water, halfway in and halfway out of the water. In a few days, the tubers will start to sprout roots and slips. When the slips have 4 leaves, clip them off and put them in another jar of water 1/2 full. The slips will begin to grow roots, when the single roots start to have small branches on them, take them out of the water and plant them in dirt in a container. I use tapered slick "dixe" cups, because you do not need drainage holes (no mess) and the slick cups make getting the plants out easy. I reuse the cups as long as they aren't severely broken. For the last plants, I just plant the whole tuber. In the garden, I hill up two ridges 3 to 4 feet apart and as long as the number of plants. I usually plant 50 plants, each plant about 16" apart. Water well as needed, if you get twisted curly tubers, that usually means not enough water. I usually harvest in late September (SW Missouri) with a potato fork. After the weather turns cool, they don't grow much, and in October sometimes the mice have a tendency to munch on the tubers, then the garden snakes follow and munch on the mice, and then it makes for fun digging, but hey the snakes are doing their job. I really like the variety that I grow, I do not know what it is, my mom started growing it 30 years ago, after trying several different varieties, and we still got it. It's "best" characteristics is good size, high production, great taste, fine grain and the tubers grow underneath the original plant. Nothing more frustrating than digging taters that are all over the place. Production is usually 10-12, 5 gallon buckets. After harvest, I spread them out on the lawn and hose the dirt off them. I let them dry and put them into paper sacks and then into the big pantry in the game room. Winter temperatures there are probably in the 65-70 degree range. They keep until the following year, and then we start all over again.
Hi,
I grew sweet potatoes two years ago and was unable to cure them due to harvesting them in November when the temperature is cool and air is dry. Is there a way to cure them for 10-14 days in this northern environment? My basement is humid but not 80-90%. I don't think I could leave them in a bathroom with a small heater for 2 weeks. Any other alternatives?
Thanks
Sweet potatoes have thin, delicate skin that is easily damaged. Curing not only adds a little sweetness, but also allows time for cork to form over injuries, thereby lessening the chance of rot, and prevents the tuber from drying out. This process will take longer at lower temperatures, thereby increasing the chance for diseases to enter any wounds; humidity lower than about 70 percent also will slow healing and affect tuber quality. Gardeners have come up with some clever ways to provide the necessary heat and humidity. Some people do indeed use a small heater in a small room (such as a bathroom) or shed, with a source of humidity, such as a pail of water or a humidifier (or in the bathroom, running the shower every so often). You’d need to monitor the temperature to make sure that it doesn’t get too hot or cold. If you have a greenhouse, then that also would be an option. Some put the potatoes in slatted or cardboard boxes covered loosely with plastic bags (make sure the plastic has a few holes so that there is some ventilation but still a humid environment), and place them in the furnace room or near a small heater. Garden author Nancy Bubel once wrote that she cures her sweet potatoes by simply spreading the potatoes behind her woodstove and covering them with a well-wrung-out towel. Hope this helps!
We have been growing sweet potatoes in a raised bed for the last few years and getting great crop(~100 lbs) every year, until this year. We dug up our bed today and found only a few (~5 lbs) sweet potatoes.
We are puzzled by what happened to the sweet potatoes. The plants were very healthy and we were expecting a bumper crop. One thing I did notice over the summer is that there were lots of ants on the leaves, although the leaves looked pretty healthy. Did the ants eat the potatoes? When we dug up the garden today, we did not see any ants.
We are really disappointed by this and are wondering if we should grow them again next year. Any help would be greatly appreciated.
Thanks.
