How to Grow Sweet Potatoes
Updated: Sep 15, 2022
This root vegetable is much sweeter than a regular potato, hence its name. They’re also quite nutritious and good for your immune system, as they’re high in vitamin A along with other vitamins and minerals. Sweet potatoes are delicious in soups, when roasted, and when baked with spices.
To help ensure your Sweet Potatoes thrives, we’ve put together this how-to video and transcript covering topics like:
Varieties of Sweet Potatoes available
Starting your Sweet Potatoes seeds
Caring for Sweet Potatoes at all stages
Fertilizer and Mulching
Transplanting best practices
Sweet Potato Companion Plants
Pests, Diseases and what to do about them
Harvesting and storing your Sweet Potatoes
Listen to this Article:
Glossary of sweet potato terms
Any plant that has trailing stems or runners is known as a vine. They can reach up to 10 feet long and are most often used as a trailing accent in containers. They can also be used as a ground cover, or grown up a trellis.
Shoots that are grown from a mature sweet potato. They’re cuttings that can grow roots, eventually growing into a new sweet potato.
NOTE Sweet potatoes are not true potatoes. What is harvested from the sweet potato is a tuberous root, as opposed to a white potato which is a tuber. The young leaves and shoots of a sweet potato can also be eaten as greens.
SWEET POTATOES VS. YAMS
Sweet potatoes are also sometimes confused with yams.
“True yams” are rarely found in American grocery stores and are starchy, dry tubers from
Africa. They have a cylindrical shape with blackish or brown, bark-like skin and white, purple, or reddish flesh. You can often find them in specialty stores.
In American grocery stores, you’ll often find two different type of sweet potatoes: firm and soft. These stores will often call the firm type a sweet potato, and the soft type a yam to differentiate the two - even though neither is a true yam.
To add more to the confusion, it’s the soft sweet potato with the deep orange flesh and copper skin that we usually plant and eat… even if stores call it a yam. Just be sure to look carefully at the flesh and skin to confirm which is which.
Varieties of sweet potato
There are quite a few varieties for you to choose from, and most of them take about 100 days to become harvest-ready.
This variety takes 100 days to harvest, and has light purple skin with a dark orange flesh. It was developed at Louisiana State University in 1987, and is an extremely high-yielding variety.
Similar Varieties: Centennial With orange skin and flesh, this variety is resistant to internal cork and wilt, takes 100 days to mature, and keeps well in storage. Georgia Jet A red-skinned variety with orange flesh. It’s somewhat tolerant to cold, and takes 100 days to mature.
O’HENRY AND WHITE YAM
A variety with white/cream-colored flesh and skin. These are both high yielding sweet potatoes with good flavor. White Yam produces smaller tapered roots, while O’Henry produces larger roots with a shape similar to Beauregard.
BUSH PORTO RICO
A variety with compact vines, copper skin, and orange flesh. It take 110 days to mature, and produces a heavy yield.
Similar Varieties: Jewell This variety has orange flesh, yields well, and takes 100 days to mature. It also keeps extremely well in storage.
This type has deep orange flesh and garnet-colored skin with an unusually rough texture. It produces moderate yields.
A compact bush type, this variety has golden skin, orange flesh, and its young leaves are purple. Typically, it takes a bit longer to mature than other varieties at about 110 days.
Starting your sweet potato "seeds"
Technically, sweet potatoes aren’t started by seeds, but rather by slips – which are shoots from a mature sweet potato.
Slips can be started by taking a disease-free, fully grown sweet potato from last year’s crop or the supermarket.
First, you’ll want to wash it to remove any anti-sprouting chemicals that a grocery store might have applied. Next, suspend a healthy root – with the pointed end facing up – with toothpicks in a glass of water. In a few weeks, there should be new growth.
Make sure to change this water routinely, as it will turn foul after about a week. The sweet potato root will sprout slips after a couple weeks, and will look like green shoots with exposed roots. When they’re 3 inches or more, these slips can either be planted directly in the field, or planted in a pot to start a transplant. For best results, the soil in its pot should be at least 65°F.
It’s important to note that sweet potatoes are storage roots, not tubers, so new shoots will emerge along the entire root, and one sweet potato should yield about 12 plants.
It’s important to note that sweet potatoes are storage roots, not tubers, so new shoots will emerge along the entire root. One sweet potato should yield about 12 plants.
It’s important to note that sweet potatoes are storage roots, not tubers, so new shoots will emerge along the entire root. One sweet potato should yield about 12 plants.
The process from bedding to planting takes about six weeks, so here are some tips for growing your own:
Buy certified seed stock at a garden center, or your favorite varieties from a market. Cover the bottom of an 8-inch deep container or box with 2 to 3 inches of sand or soil-less growing mix, and make sure your container has drainage holes.
Slice the roots lengthwise and place them (with their cut side down) in the container. Then, cover with 2-4 inches of sand or growing mix.
Be sure to keep the roots moist and warm (75-85oF), and keep them covered with plastic until your plants emerge.
Once they’ve emerged, you can remove the plastic. Now, you can grow your plants directly under cool, white fluorescent tubes for 14-16 hours a day.
Next, pull slips from your bedded roots and plant them after the danger of frost has completely passed. Keep in mind that slips are rootless when pulled from the mother root, and you’ll want to keep them well-watered.
Caring for sweet potatoes
We’ll tell you everything you need to know about watering, weeding, and hilling best practices, plus how to fertilize and mulch your crop. We’ll also share which plants grow well with sweet potato, and which structures you can use.
Sweet potatoes’ ideal soil pH is between 5.5-6.5 while their preferred soil temperature is between 70-80oF.
Meanwhile, their minimum air temperature is between 65-95oF. Sweet potatoes prefer light, sandy soils but will grow well in heavier soils that are high in clay content.
You’ll want to set your plants 12-18 inches apart in the row, then gently firm the soil around each one.
Water them immediately to establish good soil-to-root contact – and if you like, you can water them using a starter-solution (1-2 tablespoons of a 12-12-12 fertilizer, per gallon of water).
Plant your slips after your soil has warmed up to at least 65oF. Your sprouts should be placed a foot apart in rows that are spaced about 40 inches apart.
If possible, plant them in ridges to allow your soil to warm up faster in the spring.
This will also improve water drainage while giving your roots lots of room to expand. Plus, ridging makes harvesting easier.
Start weeding your sweet potato beds about 2 weeks after planting to keep weeds down.
Remember to reshape your beds with soil or mulch afterward, and you’ll also want to avoid deep digging with a hoe or other tools that could disturb the feeder roots of your plants.
Remember to keep your plants watered weekly, especially during mid-summer.
Deep watering in hot, dry periods will help to increase your yields - but if you’re planning to store some of your potatoes, don’t give your plants any extra water late in the season. If you do, it can cause the tuber’s skin to crack.
For good harvests, don’t prune the vines because they should be quite vigorous.
When the above-ground portion of your plant is about 12 inches (30cm) tall, “hill up” the soil about 6 inches (15cm) around your plants.
It’s okay to cover green leaves, so don’t worry if you do. Straw or grass mulch also works well in this process, which can be repeated up two or three times.
FERTILIZING AND/OR MULCHING
Go easy on the nitrogen fertilizer since too much will produce beautiful vines but few roots.
You’ll want to side-dress your sweet potato plants 3-4 weeks after transplanting with 3 pounds of 5-10-10 fertilizer per 100 feet of row. If you have sandy soil, then it’s best to use 5 pounds.
Also, side-dress with nitrogen or 3 tablespoons of a 10-10-10 fertilizer per 10 feet, doing so once or twice during the growing season.
Sweet potatoes respond well to ground-warming black plastic mulch. What you can do is lay this sheet of plastic tight against the soil, and then plant your slips into holes that are cut in the plastic.
It’s possible to produce good yields without using plastic mulch, but the warming mulch extends your growing season by a few weeks, which can increase your yields dramatically (which is great news.).
TRANSPLANTING BEST PRACTICES
Any sweet potato slips that are grown indoors need to be hardened-off first before transplanting. Gradually expose them to the strong summer sun over a period of 1-2 weeks – a task you can easily do by placing the mother plants in warm filtered shade.
GROWING STRUCTURE OPTIONS
Make sure you have a sunny spot to use, with loamy, well-drained soil. Sweet potatoes aren’t too picky, but they do prefer soil on the sandier side. They also need plenty of air space in the soil for their roots to reach down.
If your soil is clay, rocky, or compacted, consider using raised beds to grow your sweet potatoes.
THINGS TO KEEP IN MIND
You’ll want to pick a spot with plenty of room for your sweet potato vines to run – about 3 feet between rows should do the trick.
If you live in the northern US or in Canada, consider covering your growing area with fabric mulch about 3 weeks before planting.
This helps to warm the soil, which your sweet potatoes will love.
It’s best to till your garden area to a depth of 8-10 inches, then create raised mounds that are 6-8 inches tall and about 12 inches wide using fertile, well-drained soil.
If you’ve got poor soil, make sure to amend it based on what it needs. Consider using natural fertilizers like compost or manure, because sweet potatoes are extremely sensitive to aluminum toxicity.
COMPANION PLANTS DO’S AND DON’TS
As a rule of thumb, root vegetables like parsnips and beets are good companions for your sweet potatoes.
Bush beans also make great companions, and certain varieties of pole beans can be trained to grow along the ground intermingled with sweet potato vines.
Also, aromatic herbs like thyme, oregano and dill are good sweet potato companions.
Squash is something you won’t want to grow with your sweet potatoes.
Common challenges and their solutions
There are a number of pests and diseases that can potentially harm your sweet potatoes.
Not to worry – we’ve listed them here below, as well as how to either avoid or fix the problem.
These pests are usually a problem for the undersides of leaves and/or stems of your plant. They tend to feed in groups, and often spread diseases.
Solution: Use a strong jet of water to wash them off your plants. Neem oil, insecticidal soaps, and horticultural oils are also effective against aphids - just be sure to follow the application instructions on the packaging.
Oftentimes, you can also get rid of aphids by wiping or spraying the leaves with a mild solution of water and a few drops of dish soap (one variation includes adding a pinch of cayenne pepper).
Soapy water should be reapplied every 2-3 days for about 2 weeks.
These pesky flies eat your plants, will group together on the undersides of leaves, and fly up when disturbed.
Solution: Remove any affected leaves, or the whole plant if it’s severely infested. Introduce beneficial insects into your garden, use yellow sticky traps, and apply insecticidal soaps or oils.
Keep in mind that these oils (like neem oil) might reduce whitefly numbers, but they won’t eliminate them entirely.
SWEET POTATO STEM BORER
These larvae burrow into the stem that leads to your plant’s storage roots. They feed in the crown region, which causes your plant to wilt, yellow, and then die.
Solution: Keep your field free from weeds, especially ipomoea weeds. You can also try fallowing your land for a few seasons (aka taking a break from planting) if the infestation is too severe.
Also, use insect free planting material, and pheromone traps to monitor and control these pesky borers.
The main pest of sweet potato, it’s found in all of the growing regions for this crop around the world. Weevils can’t dig, so they get to the roots through cracks in the soil when it dries out. They might also follow a vine down into the soil and move along the root system until they come across a storage root.
Solution: Hilling up the soil around the base of your plant and on the sides of the ridges can help prevent or fill soil cracks.
When conditions are dry and the soil cracks, sweetpotato weevil damage can become a serious problem since they can more easily reach the roots.
You’ll also want to practice good field sanitation by carefully removing and destroying (either by burning or feeding to livestock) all old vines or root residues that may be left in your garden.
This process can help break the sweetpotato weevil’s life cycle.
It’s also important to use clean (uninfected) shoots and slips. Weevils tend to lay their eggs in the older woodier parts of the vine, so cuttings should only be taken from your healthy looking plants.
Also, allowing predatory natural enemies like ants, earwigs, ground beetles and spiders to move through your sweet potato fields can help keep weevil numbers under control.
You can even move ant nests closer to your sweet potato patch.
Finally, using a barrier crop like cassava, maize, bananas or sorghum in strips that are at least 3‐5m wide between your old and new sweet potato fields can help, since it reduces the number of weevils that might be migrating to your newly planted crop.
This pest feeds on the underground parts of your plant, including the main stem and roots, and also feed on the tubers by making tunnels. This will wilt your plant, and eventually it will die.
Solution: Practice deep summer ploughing to expose any grubs that may be present in your soil, while also making sure it has good drainage.
Also, follow crop rotation with soybeans to reduce these grub populations. Finally, there are some safe bacteria you can introduce into your garden to kill off the grubs.
ALTERNARIA LEAF BLIGHT
Small, yellow-brown spots with a yellow or green halo will first appear on the oldest leaves. As the disease progresses, leaves will begin to curl and eventually will die. This disease is common in growing areas with high temperatures and frequent rainfall.
Solution: Water your plants from below to avoid having soil splash up onto the lower leaves.
If you can water from below using a soaker hose or drip irrigation AND provide a well-ventilated cover for your plants to protect them from the rain, you’ll be all set.
Be sure to clean any equipment between uses to prevent the spread of bacteria, and do not prune or handle your plants when they’re wet. Also, establish a crop rotation and stick to it.
If you do spot some blighty leaves (usually on the bottom of the plant closest to the soil), remove and destroy them.
Finally, you can try spraying the leaves of your plant with a baking soda solution (1 tbsp baking soda, 2.5 tbsp of vegetable oil, and a tsp of liquid soap to one gallon of water) or neem oil.
Just take care not to use neem oil when pollinating insects like bees or other beneficial insects are present. You’ll want to spray only a few leaves to start, then check for a reaction before applying every two weeks.
A disease that causes the stunting, wilting, and yellowing of your plants. Leaves might drop, and your plants can eventually die. You’ll also notice circular brown-black patches of rot on the tubers, which can continue to develop in storage.
Solution: Only plant disease-free cuttings, and avoid planting them in spots where sweet potatoes were previously grown in the past 3-4 years.
Before you plant them, you can even try treating them with certain fungicides first.
FUSARIUM ROOT AND STEM ROT
This disease causes the stems of your plant to swell and become distorted at their base. Also, deep, dark rot will grow into the tuber and form cavities, while there’s also a growth of white mold. Typically, this disease is spread by infected transplants.
Solution: You can prevent the issue by planting disease-free roots, or by using cut transplants rather than slips.
Also, practice crop rotation and treat your seed roots with an appropriate fungicide before you plant.
LEAF AND STEM SCAB
Small brown lesions will grow on the leaf veins, which then become corky in texture, causing the veins to shrink and the leaves to curl. Lesions on the stem are slightly raised and have purple to brown centers with light brown edges. Also, scabby lesions will form on the stems when all of the smaller lesions come together.
Solution: Avoid overhead watering, and rotate your sweet potato with other crops. Also, use only disease-free cuttings/slips and destroy any crop residue immediately after you harvest.
Certain fungicides can also help to control this disease.
SWEET POTATO VIRUS DISEASE (SPVD)
A disease that’s caused by two viruses: sweet potato chlorotic stunt virus (SPCSV) and sweet potato feathery mottle virus (SPFMV). It causes the severe stunting of infected plants, and distorted discoloration on the leaves. You might also notice some feathery purple patterns on the leaves.
Solution: Use healthy cuttings for planting, and practice crop rotation. Control any aphid or white fly populations too, since they spread the disease, and be sure to remove and burn any infected plants.
Harvesting and storing
Sweet potatoes generally mature in 85-120 days, and we recommend checking their root size after 80-85 days.
For best quality, harvest your tubers when they reach about 5-6 inches in length and about 2 inches in diameter. Harvest the roots as soon as they reach eating size, and before any frost is set to arrive.
Digging up your sweet potatoes will be much easier if you cut their vines off first. Then, use a garden fork or spade to loosen the soil and gently lift up and expose your sweet potatoes.
Make sure you handle them with care, gently removing any attached soil clumps. Don't rub the skin or wash the roots before storing them inside, and if the weather is dry, you can let them sit on the ground for several hours before bringing them in.
NOTE If the vines are exposed to frost, dig the roots up immediately because any decay in dead vines will pass down to the roots. If you can’t immediately dig, then cut away the vines and throw some loose soil over your rows to protect them from the cold (temperatures below 55°F can cause chilling injury).
In general, you should yield 20-40 pounds for each 10-foot row.
To cure your sweet potatoes for storage, they’ll need a temperature between 80-90°F (26-32°C) plus high humidity for 5-10 days.
Once cured, sweet potatoes should be stored at about 60°F in a spot with high humidity.
Under these conditions, some varieties can actually be stored for up to a year.
Their sugar content will slowly increase in storage, but roots will shrivel and sprout if temperatures are too high, so keep that in mind.
Also, roots will usually store successfully even without the one-week curing process – so if you don’t get the chance to cure your sweet potatoes, don’t stress.