Sweet potatoes are not usually planted the same way as are white potatoes. Planting white potatoes in the early spring means putting a whole sweet potato in the ground. The cold weather will stop the sweet potato from growing, and it might even go bad. Because of this, planting “slips” after the last frost date is the best way to make more sweet potatoes. Slips are the rooted sprouts that grow out of the sweet potato tuber. You can buy seeds from a reputable company, but it’s much more fun to grow them yourself! Kids will also find this a fun and interesting thing to do in the garden.
One potato tuber will often produce more than a handful of sprouts or slips. You can carefully twist these slips off of the original tuber or cut them off while they are still attached to the tuber. Each of those slips can grow into a plant that can produce about 6 sweet potatoes. It generally will take about 6 weeks for the sprouts to be ready to slip off the tubers. In Central Virginia, you can plant after the last frost date. To be safe, I plant in the third week of May. So, you should start the slips the first week of April. By the third week of May, they’ll be ready to plant in the garden.
For the past 10 years, I have been using the following procedures to grow Japanese sweet potato slips. But any kind of sweet potato can be used. We grow the Japanese variety only because we love the less sweet flavor, and the drier texture. During the first week of April:
Red sprouts will start to grow from the sides and tops of the tubers after two to three weeks. After this point, you can take off the plastic cover and keep the tray of sprouting potatoes moist. Soon, these stiff sprouts will begin to leaf out and grow roots. The roots will be attached to the seed potato.
The sprouts will continue growing roots underneath the sliced tuber. Sprouts are ready to be “slipped” off the tuber when they have a few green leaves and roots hooked up to them. This can be accomplished with a twist of the sprout. I prefer to slice the potato, in between the sprouts. Using this method, each sprout and some root will be attched to a small piece of potato. I do this because if I try to pull or “slip” it off the potato, sometimes it breaks. This is another good reason to use one more seed potato than you think you will need so you have extra.
If it’s been more than a week since the last frost, the potatoes can be planted in the garden bed that was already ready. If not, you can plant them in small pots and keep them inside under grow lights until the last frost date.
Even after the last frost date, I like to grow the slips in pots for about two weeks. This extra step gives the slips a chance to develop larger leaves and a stronger root system. It takes a little more work and time, but I have never lost a plant in the row when I do it this way.
I have always been able to count on at least 6 healthy slips from each tuber. Oftentimes, there will be more. Each of those slips will mature into a plant that produces, on average, 6 tubers. And each plant is spaced about a foot apart in the garden. To be sure I will get a certain number of potatoes, I need to do some simple math.
I like to consume 2 potatoes per week : 2 times 52 weeks equals 104 tubers.
— 104 divided by 6 potatoes from each plant equals 18 plants, rounded up. I will need 18 slips.
18.18 slips divided by 6.06 slips per seed potato equals 3 seed potatoes (remember that the seed potatoes are cut in half to make slips).
Somewhere in my garden, the vines will be able to grow at least 4 feet away from the main plant in every direction. This is because of the extensive vining habit of sweet potato plants. I need an 18-foot row or two or three shorter rows because the garden plants should be spaced out 1 foot apart.
Below is a photo of the slips that have been growing in small pots. They are all lined up and ready to be transplanted into my row. In one year, squirrels dug holes in the row and ate all the potatoes. After that, we put black landscape fabric over the row to keep the water in and the squirrels out. It also prevents weeds from growing in between the vines.
As the vines begin to grow, the soil will soon be blanketed by them. Every direction, the vines will grow three to four feet! To help them “take over,” put an 18-inch stake in the ground in front of or behind each plant. As the vines grow, it can be hard to know where to water if you don’t mark each spot. Putting the stakes down also makes it easier to find each plant later in the fall, when the vines need to be cut off.
The plants will have grown in the ground from mid-May to mid-October, or at least until the first frost. Then it will be time to get the area ready for harvest. We follow these steps because the vines are so thick and tangled. This makes the whole process easy and fun.
1. Starting about a foot away from each rooted plant, cut away the vines. We use a garden shear.
2. Pull them to the sides of the row so you can easily access the tubers.
3. Whatever bit of vine remains attached to the tops of the plants can now be cut away.
Dig around the plant slowly in a wide circle with a trowel, being careful not to cut any potatoes. I scrape some soil away from the main plant as I also tug on the remaining stalks. Soon they will be there! You’ve been waiting all season, and now they are finally ready. They grow as a cluster, attached to the main stem of the plant. Lift them out one at a time with your trowel, or if the ground is loose, pull on the main stalk and they will all come out at once, still joined.
At this point, the potato skins are easily scratched. To harden the skins, leave the potatoes in the row for a few hours to begin to dry. The next step is to rub the dirt off gently. A soft cloth or your hands work best for this.
If you don’t cure the potatoes the right way, they will get soft before you can eat them all. For about 10 days, the potatoes should stay at a temperature of 75° to 80°. Putting the potatoes on a table in a room with an electric heater is one way to do this. Once the time for curing is over, they can stay in a basement or another room that stays between 60° and 65°F.
Growing sweet potatoes from seed can seem intimidating for some gardeners, but it is actually quite straightforward once you understand the process While sweet potatoes are typically propagated from cuttings called slips, growing sweet potatoes from true seed is an alternative method that can offer certain advantages In this detailed guide, I’ll walk through the entire process of growing sweet potatoes from seed, from selecting and starting seeds, to transplanting, caring for the plants, and harvesting a bountiful crop.
Why Grow Sweet Potatoes from Seed?
Most gardeners are accustomed to propagating sweet potatoes from slips, which are cuttings taken from an existing sweet potato This is certainly the most common way to grow these tasty tubers However, growing sweet potatoes from seed has some potential benefits
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Greater genetic diversity – Seed grown plants have a more diverse genetic makeup than cloned slips. This can result in novel shapes, flavors and colors.
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Disease resistance – Seed grown sweet potatoes may have increased disease resistance compared to cloned plants.
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Ease of transport – Sweet potato seeds are much easier to mail and transport than live slips or bulky tubers. This makes obtaining new genetic material easier.
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Flexible timing – You can start sweet potato seeds indoors anytime without being dependent on transplant availability.
So while growing from slips is certainly still a good option, don’t rule out seed propagation. It just takes a bit of planning and patience. Now let’s get into the specifics of how to grow sweet potatoes from seeds.
Selecting Sweet Potato Seed
Obviously, the first step is obtaining viable sweet potato seed. There are a few options here:
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Purchase seed – There are many reputable seed companies that sell sweet potato seed of known varieties. This ensures you are starting with high quality, viable seed.
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Save your own seed – If you grew sweet potatoes in your garden last year, you can save some tubers to produce seed for the next season. To do this, cure tubers properly after harvest then store them over the winter in a cool, dry place. The following spring, transplant sprouted tubers to an isolated area and allow them to flower and set seed.
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Wild seed – It is possible to collect seed from wild sweet potato plants, though viability and genetics are less predictable. Use wild seed only as a last resort.
I recommend purchasing high quality seed from a trusted supplier until you gain experience with growing sweet potatoes from seed. This will maximize your chances of success on the first try.
Starting Sweet Potato Seeds Indoors
Sweet potato seeds have a relatively long germination period of 4-6 weeks. It’s best to get seeds started indoors about 8 weeks before your last expected spring frost.
Here are some tips for starting sweet potato seeds:
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Use a sterile seed starting mix in seed trays or containers. Moisten the mix well before planting.
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Plant seeds 1⁄4-1⁄2 inch deep. Sweet potato seeds need light to germinate, so don’t cover too deeply.
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Maintain warm soil temperatures of at least 75°F. Consider using a heat mat.
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Keep seeded containers in bright indirect light. A sunny windowsill works well.
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Keep soil evenly moist but not saturated. Use a spray bottle to mist soil as needed.
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Once sprouted, grow seedlings on at about 70-75°F until transplanting.
Follow these tips and you should see sprouts emerge in 4-6 weeks. Provide ample light and space once germinated as seedlings grow quickly. Harden off plants before transplanting just as you would any other seedling.
Transplanting Sweet Potato Seedlings
Sweet potato plants prefer warm, sunny conditions. Transplant seedlings into the garden after all danger of frost has passed. Here are some tips for transplanting:
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Space plants 12-18 inches apart in rows 3 feet apart. Sweet potatoes need wide rows.
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Dig holes or trenches for seedlings as you would for tomato transplants.
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Gently remove seedlings from containers, disturbing roots as little as possible.
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Plant seedlings at the same level they grew in containers.
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Water newly planted seedlings well.
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Consider using row covers or cloches to boost warmth and growth.
Choose a spot that gets full sun whenever possible. In very hot climates, afternoon shade can be beneficial. Transplant on a cloudy day or in late afternoon to prevent wilting. With a little TLC, your seedlings will establish quickly.
Caring for Seeded Sweet Potatoes
Seeded sweet potatoes need similar care to those grown from slips. Follow these tips for robust growth:
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Water 1-2 inches per week. Avoid overwatering.
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Use mulch such as straw to retain moisture and reduce weeds.
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Fertilize with a balanced organic fertilizer or compost tea every 2-3 weeks.
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Hill soil up around plants as they grow to encourage tuber formation.
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Remove any flowers or seed pods to direct energy to the tubers.
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Monitor for common pests like aphids, beetles and borers. Use organic controls as needed.
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Cut back watering about 2 weeks before harvest to improve curing.
Sweet potatoes are not heavy feeders but do require consistent moisture. Monitor closely and act fast if pests like sweet potato weevils appear. Maintaining optimal growing conditions will ensure your seeded sweet potatoes size up nicely.
Harvesting and Curing Seeded Sweet Potatoes
Seeded sweet potatoes take 100-140 days to mature depending on the variety. Here are some signs tubers are ready to harvest:
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Vine growth slows and leaves begin yellowing.
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Skins are firm with no splits or cracks when gently pressed.
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Temperatures cool consistently below 70°F for several weeks.
Use a garden fork to gently loosen soil and lift plants. Remove tubers by hand taking care not to bruise or injure them. Cure sweet potatoes for 5-7 days at 80-85°F and high humidity before long term storage. This helps heal cuts, thicken skins, and convert starches to sugars. Store cured tubers in a cool, dry place with good ventilation.
With seed grown sweet potatoes, you never know what novel shapes, colors and flavors you might discover when harvesting. Part of the fun with growing sweet potatoes from seed is the diversity.
Troubleshooting Seeded Sweet Potatoes
Growing sweet potato from seeds does involve some unique challenges. Here are some potential issues and solutions:
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Poor germination – Ensure seeds are fresh and stored properly. Maintain optimal soil temp and moisture.
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Leggy or weak seedlings – Provide ample light and moderate temperatures after germination.
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Slow growth after transplanting – Transplant on a cloudy day and water well to reduce shock. Warm soil and plenty of sun accelerates growth.
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Misshapen or bitter tubers – Maintain consistent soil moisture and proper curing conditions. Select improved varieties bred for quality.
Don’t get discouraged by setbacks. Often it just takes refining your process over a few seasons to get excellent results with seeded sweet potatoes.
Final Thoughts on Growing Sweet Potato Seed
While growing sweet potato slips may still be the norm for many gardeners, using true seeds is an intriguing alternative method. With proper planning and care, seeded sweet potatoes can produce plentiful yields of diverse and delicious tubers. If you’ve never tried growing sweet potatoes from seed, give it a go this year. Just be sure to purchase high quality seed, pay close attention to plants needs, and allow plenty of time. You’ll soon discover the joys of harvesting homegrown sweet potatoes raised from seed.
Piedmont Master Gardeners • Sharing knowledge, Empowering communities PMG News
- By Barbara Gardino
- /
- March 2023-Vol. 9, No.3
- /
Sweet potatoes are not usually planted the same way as are white potatoes. Planting white potatoes in the early spring means putting a whole sweet potato in the ground. The cold weather will stop the sweet potato from growing, and it might even go bad. Because of this, planting “slips” after the last frost date is the best way to make more sweet potatoes. Slips are the rooted sprouts that grow out of the sweet potato tuber. You can buy seeds from a reputable company, but it’s much more fun to grow them yourself! Kids will also find this a fun and interesting thing to do in the garden.
One potato tuber will often produce more than a handful of sprouts or slips. You can carefully twist these slips off of the original tuber or cut them off while they are still attached to the tuber. Each of those slips can grow into a plant that can produce about 6 sweet potatoes. It generally will take about 6 weeks for the sprouts to be ready to slip off the tubers. In Central Virginia, you can plant after the last frost date. To be safe, I plant in the third week of May. So, you should start the slips the first week of April. By the third week of May, they’ll be ready to plant in the garden.
To begin the process, have these materials available:
- If you can, buy organic sweet potatoes, whether you buy them in a store or as “seed” potatoes from a seed company.
- a strong knife to slice each tuber in half
- a cutting board or a piece of wood (the picture shows a piece of 2×4 that we happened to have in the greenhouse!)
- I buy mine in the baking section of a grocery store. At least one aluminum baking tray with a lid.
- organic seed starter mix that you have already wet; enough to cover the potatoes and fill the tray.
For the past 10 years, I have been using the following procedures to grow Japanese sweet potato slips. But any kind of sweet potato can be used. We grow the Japanese variety only because we love the less sweet flavor, and the drier texture. During the first week of April:
- Fill a tray with a moistened organic growing medium
- Place the potato on a cutting board and cut it in half along the length.
- Place one half on the planting medium with the cut side facing down.
- Fill the potato with the mix and cover it with a little more of it.
- Place the plastic lid on top of the tray in a way that lets air flow.
- Keep the tray under shop lights or grow lights, and make sure the soil doesn’t get too dry.
- You can also place the tray by a sunny window
- You can put the tray on a heating mat for plants to speed up the process. This is an optional step.
Red sprouts will start to grow from the sides and tops of the tubers after two to three weeks. After this point, you can take off the plastic cover and keep the tray of sprouting potatoes moist. Soon, these stiff sprouts will begin to leaf out and grow roots. The roots will be attached to the seed potato.
The sprouts will continue growing roots underneath the sliced tuber. Sprouts are ready to be “slipped” off the tuber when they have a few green leaves and roots hooked up to them. This can be accomplished with a twist of the sprout. I prefer to slice the potato, in between the sprouts. Using this method, each sprout and some root will be attched to a small piece of potato. I do this because if I try to pull or “slip” it off the potato, sometimes it breaks. This is another good reason to use one more seed potato than you think you will need so you have extra.
If it’s been more than a week since the last frost, the potatoes can be planted in the garden bed that was already ready. If not, you can plant them in small pots and keep them inside under grow lights until the last frost date.
Even after the last frost date, I like to grow the slips in pots for about two weeks. This extra step gives the slips a chance to develop larger leaves and a stronger root system. It takes a little more work and time, but I have never lost a plant in the row when I do it this way.
Determine how many slips and potatoes are needed.
I have always been able to count on at least 6 healthy slips from each tuber. Oftentimes, there will be more. Each of those slips will mature into a plant that produces, on average, 6 tubers. And each plant is spaced about a foot apart in the garden. To be sure I will get a certain number of potatoes, I need to do some simple math.
I like to consume 2 potatoes per week : 2 times 52 weeks equals 104 tubers.
— 104 divided by 6 potatoes from each plant equals 18 plants, rounded up. I will need 18 slips.
18.18 slips divided by 6.06 slips per seed potato equals 3 seed potatoes (remember that the seed potatoes are cut in half to make slips).
Determine the amount of space needed
Somewhere in my garden, the vines will be able to grow at least 4 feet away from the main plant in every direction. This is because of the extensive vining habit of sweet potato plants. I need an 18-foot row or two or three shorter rows because the garden plants should be spaced out 1 foot apart.
Below is a photo of the slips that have been growing in small pots. They are all lined up and ready to be transplanted into my row. In one year, squirrels dug holes in the row and ate all the potatoes. After that, we put black landscape fabric over the row to keep the water in and the squirrels out. It also prevents weeds from growing in between the vines.
As the vines begin to grow, the soil will soon be blanketed by them. Every direction, the vines will grow three to four feet! To help them “take over,” put an 18-inch stake in the ground in front of or behind each plant. As the vines grow, it can be hard to know where to water if you don’t mark each spot. Putting the stakes down also makes it easier to find each plant later in the fall, when the vines need to be cut off.
Prepare the area for harvesting
The plants will have grown in the ground from mid-May to mid-October, or at least until the first frost. Then it will be time to get the area ready for harvest. We follow these steps because the vines are so thick and tangled. This makes the whole process easy and fun.
1. Starting about a foot away from each rooted plant, cut away the vines. We use a garden shear.
2. Pull them to the sides of the row so you can easily access the tubers.
3. Whatever bit of vine remains attached to the tops of the plants can now be cut away.
Begin harvesting
Dig around the plant slowly in a wide circle with a trowel, being careful not to cut any potatoes. I scrape some soil away from the main plant as I also tug on the remaining stalks. Soon they will be there! You’ve been waiting all season, and now they are finally ready. They grow as a cluster, attached to the main stem of the plant. Lift them out one at a time with your trowel, or if the ground is loose, pull on the main stalk and they will all come out at once, still joined.
At this point, the potato skins are easily scratched. To harden the skins, leave the potatoes in the row for a few hours to begin to dry. The next step is to rub the dirt off gently. A soft cloth or your hands work best for this.
Cure the potatoes for winter storage.
If you don’t cure the potatoes the right way, they will get soft before you can eat them all. For about 10 days, the potatoes should stay at a temperature of 75° to 80°. Putting the potatoes on a table in a room with an electric heater is one way to do this. Once the time for curing is over, they can stay in a basement or another room that stays between 60° and 65°F.
Now you can enjoy your harvest!
Helpful resources for all aspects of growing sweet potatoes:
In the Edible Garden
From Spring Slips to a Bountiful Fall Harvest
In the Ornamental Garden
Most insects in the flower garden are harmless and many are actually beneficial. But a few insect species are capable of doing significant damage.
March is the beginning of our outdoor gardening season. Lets review some of the tasks that may need attention.
Prepare your beds, prune, sow seeds, and enjoy spring!
PMGs Spring Lecture Series on Thursdays this month!
The Ultimate Food Security Crop – How To Grow Sweet Potatoes Almost Anywhere
FAQ
How long does sweet potato take to grow from seed?
Can I grow a sweet potato from a sweet potato?
Can I just plant a sprouted sweet potato?
Can you grow sweet potato vines from seeds?