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.
Sweet potatoes are a delicious, nutritious crop that are easy and fun to grow. While sweet potato slips are commonly used for propagation, you can also grow sweet potatoes from seed. Starting sweet potatoes from seed at home is an engaging gardening activity for gardeners of all ages.
Overview of Growing Sweet Potatoes from Seed
-
Sweet potato seeds are actually dried seed pods produced by the sweet potato plant,
-
Seed pods form after the plant flowers, typically in warmer climates Pod collection requires overwintering plants
-
Each seed pod contains several hundred miniscule seeds. These are planted indoors 8-12 weeks before outdoor planting time.
-
Seedlings grown from seed show greater genetic diversity compared to those grown from slips.
-
Growing sweet potatoes from seed takes more time and care than using slips, but allows you to propagate your own unique varieties.
Collecting and Storing Sweet Potato Seed Pods
-
Allow your best producing sweet potato plants to overwinter in the garden. Provide frost protection if needed.
-
In spring, potato plants will send up vines and flower. Pollinated flowers form seed pods.
-
Collect seed pods when they turn brown and dry. Store in a cool, dry place over winter.
-
In early spring, remove seeds from pods. Place seeds in moist paper towels in a baggie until sprouting.
-
Plant sprouted sweet potato seeds in seed starting mix 8-12 weeks before your last spring frost.
Caring for Sweet Potato Seedlings
Sweet potato seeds need warm soil and high humidity to sprout and grow. Follow these tips:
-
Start seeds indoors at 70-80°F. Bottom heat speeds germination.
-
Cover seeds lightly with soil. Keep soil moist but not saturated.
-
Germination takes 1-3 weeks. Thin seedlings to 1 per cell once true leaves appear.
-
Grow seedlings under lights or in a sunny window. Maintain warm temperatures and high humidity.
-
Harden off and transplant outdoors 1-2 weeks after last spring frost date once night temps stay above 55°F.
Growing Sweet Potatoes from Seedlings
Once transplanted, care for sweet potato seedlings much like you would slips:
-
Plant 12-18 inches apart in rows spaced 3-4 feet apart. Sweet potatoes need room to sprawl.
-
Amend soil with compost to improve drainage and nutrition. Sweet potatoes like slightly acidic, sandy soil.
-
Water young plants regularly to establish. Reduce frequency once vines start spreading.
-
Apply mulch around plants to retain moisture and reduce weeds.
-
Harvest potatoes 3-4 months after transplanting when foliage starts dying back.
Advantages and Disadvantages of Seed Propagation
Growing sweet potatoes from seeds has some notable pros and cons:
Advantages:
- Greater genetic diversity versus slips from a single tuber
- Propagate your own unique varieties adapted to your climate
- Fun gardening project for seed savers and kids
Disadvantages:
- More time and care required versus using slips
- Lower germination rate than slips
- Seed not widely available; must overwinter own plants
While starting from slips may be easier, seeds let you discover new varieties suited to your exact growing conditions. Both methods yield a bountiful harvest of homegrown sweet potatoes!
Step-By-Step Guide to Growing Sweet Potatoes from Seed
Follow this simple guide for success growing sweet potatoes from seed:
Fall
-
Select your best producing sweet potato plants to overwinter for seed collection.
-
Before first frost, protect plants with cloches, fabric row covers, or bring indoors. Aim to keep soil temp above 55°F.
-
Overwintered plants will return in spring to produce flowers and seed pods.
Winter
-
On dormant plants, carefully collect any dried seed pods that formed during summer growth.
-
Store pods in a cool, dry place over winter. Label pods by variety if saving seeds from multiple plants.
Early Spring
-
Gently open pods and separate seeds from debris. Place seeds in damp paper towel and store in a baggie.
-
Check seeds daily. Plant sprouted seeds in starter trays as soon as the root radical emerges.
-
Grow seedlings at 70-80°F under lights with humidity domes to retain moisture.
Spring
-
Transplant seedlings into garden 1-2 weeks after last expected spring frost once soil warms to 60-70°F.
-
Space plants 12-18 inches apart in rows 3-4 feet apart. Follow tips above for growing and harvesting.
-
Let a few plants flower and set pods again to collect seeds for the next season.
Don’t let collecting and saving sweet potato seeds intimidate you. With a little care and patience, you can discover exciting new varieties ideally suited to your garden!
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!
How to grow your own sweet potato slips, using store bought sweet potatoes!
Can sweet potatoes grow fro seeds?
Sweet potatoes aren’t grown fro seeds. They are grown from slips, which are a rooted portion of a mature sweet potato. To obtain a sweet potato slip, cut a sweet potato in half lengthwise and bury each half in damp potting soil. Keep the slips moist and warm, and shoots should sprout within a few days. Leaves will follow the shoots.
How does a sweet potato grow?
Sweet potatoes do not grow from seed potatoes, but rather from slips – which are miniature sweet potato plants that grow from the roots of an existing sweet potato. Starting and growing sweet potato slips is an easy and fun way to create new sweet potato plants.
How do you plant sweet potatoes?
To plant sweet potatoes, break off the lower leaves, leaving only the top ones, and set the slips deep enough to cover the roots and the stem up to the leaves. Plant the slips on a warm, overcast day when the soil temperature has reached 60°F (15°C), with 3 feet between mounds for sufficient space for the vines to run. Sweet potatoes will form on the nodes.
How do you grow a baby sweet potato plant?
To grow a baby sweet potato plant, you’ll need a bag of fresh organic sweet potatoes or some seed sweet potatoes. Cut the sweet potatoes in half or, if they’re very large, divide them into more pieces. Be sure to leave a few cubic inches of potato for each piece so the baby plant has stored energy.