How to Propagate Sweet Potatoes to Grow New Slips

Use these step-by-step instructions to propagate a sweet potato in water or potting mix. This produces “slips” (stems and leaves) providing new plants for the garden. The vines also make interesting houseplants.

Many fruits and vegetables can be propagated at home to grow new plants. This shows a simple way to grow avocado from seed.

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Sprouting Sweet Potatoes

Just one sweet potato can create a lot of new sweet potatoes—ongoing for years to come.

In the past decade or two, this carbohydrate-rich root vegetable has enjoyed a new wave of popularity, likely due to sweet potatoes offered as an alternative to traditional french fries or baked potatoes in restaurants and food trucks.

While not a type of potato, sweet potatoes (edible Ipomoea batatas cultivars) are just as versatile and sweeter—as the name implies.

Because we cannot grow sweet potatoes as perennials year-round in cold climates, we adapt by growing them as annuals (a single season crop). Planted after the risk of frost has passed, faster-growing varieties can produce a substantial harvest by early fall.

The easiest way to get started is to buy or create your own “slips.”

Slips are simply stems and leaves that grow from existing sweet potatoes to form new plants.

Start with a sweet potato from the grocery store and use the instructions below to grow your own slips.

The best time to get started is 2 to 3 months before your last frost in spring, so, by the time the weather warms, your slips are ready for transplanting outdoors.

Just one sweet potato can produce a lot of slips—a dozen is not out of the question. And each of those in turn can become a new plant that produces several pounds of sweet potatoes.

Cured and stored after harvest, you’ve got sweet potatoes for the winter and extras for creating new slips for the planting season to come. And on it goes.

If you’re not a vegetable gardener, you can still use the methods shown below to grow a fabulous vining houseplant.

Contents

• How to Propagate Sweet Potatoes
• Create Slips
  • Water Jar Method
  • Potting Mix Method
• Root the Slips
• Transplant the Slips
• Frequently Asked Questions

How to Propagate Sweet Potatoes

There are a lot of different ways to do this but each method is basically doing the same thing—providing warmth and moisture to induce sprouting. 

I have done so many experiments to see which method works best and there are definitely some clear winners which I have provided instructions for below.

Three Basic Steps

1. Create slips | Make the sweet potato produce slips indoors, 2 to 3 months before last frost.
2. Root the slips.
3. Transplant the rooted slips outside after last frost.

Two Methods

The most common method you’ll see involves suspending the sweet potato in a jar of water. This works fine. It’s also a good choice if you just want a cool-looking houseplant.

Another method which I have come to prefer is to bury the sweet potato horizontally in moist potting mix. I like this method because sometimes the slips and roots form at the same time so it skips a step.

Which type of sweet potatoes can I propagate?

• Choose any sweet potatoes from the grocery store or farmer’s market.

The only way to know for certain whether a sweet potato will propagate is to try it.

Our options are likely limited to whatever local stores sell.

Other than a sign saying Sweet Potatoes and perhaps listing the country of origin, it’s rare for the cultivar name to be listed in stores. If we had that information, we could look up the expected days to maturity to know whether it’s a good fit.

• Locally-grown sweet potatoes are the safest bet because we know they are ready to harvest within our growing season.
• Sweet potatoes from other climates may need longer to mature—more time than our short growing season offers—but, again, the only way to find out is to try it.

Some sweet potatoes may also be treated with growth inhibitors to prevent spontaneous sprouting in the store. I have not encountered this but I have only tested locally-grown sweet potatoes which likely don’t require it. My guess is some sweet potatoes grown overseas may be treated to allow longer travel and storage times.

To improve your odds, try propagating several at once, using both methods shown, and include different varieties if available. Even from the same sack of sweet potatoes, I’ve had hits and misses. Some are prolific growers while others take their sweet time or do nothing at all.

So, grow many and hope for some. And you can always give extras to friends.

Step 1 – Create Slips

Water Jar Method

Supplies

• Sweet potatoes | Make sure they are nice and firm, not mushy or dry. If they’re good enough to eat, they are good for propagation.
• Glass jar | Choose a jar large enough for the sweet potato to be suspended vertically with half of it above the water surface. Also allow extra room below the sweet potato for roots to form in the water.
• Plastic cocktail forks or strong toothpicks

Steps

• Place sweet potato vertically in jar, resting the cocktail forks on the lip of the jar. If the sweet potato has a tapered end, aim that end down into the water.
• Fill jar with warm water to just below cocktail forks
• Place jar indoors in indirect light with consistent warmth (70-85°F or 21-29°C).
• Change water every few days.

It’s not unusual to see some growth—little roots and/or buds that will become shoots—within the first week.

In 4 to 6 weeks you will likely have a few inches of roots and shoots (slips).

Potting Mix Method

Supplies

• Sweet potatoes | Make sure they are nice and firm, not mushy or dry. If they’re good enough to eat, they are good for propagation.
• Potting Mix for Vegetables | Make sure it’s made for food crops.
• Container | Choose a container that is wider than sweet potato is long and several inches deep – preferably with drainage holes. You can also use takeout food containers if you’re careful not to over-water. Sweet potatoes rot if left in standing water.
• Large plastic food bag | Or, tall, clear humidity dome/lid (optional) – if humidity in the room is low (below 50%)

Steps

• Add 1 to 2 inches of moist potting mix to container. Moisture level is right if you can form a ball of potting mix that holds its shape but it’s not so damp that water drips out when squeezed.
• Gently rinse the sweet potato under clean water, careful not to disturb any buds if there are any already.
• Lay sweet potato on its side (horizontally) in the moist potting mix.
  Alternative method: slice the sweet potato lengthwise and plant each piece cut-side down.
• Add additional moist potting mix until sweet potato is nearly or completely covered. Both ways work. I left it showing so you can see what’s happening in the photos.
• Add lid or humidity dome or place everything in large plastic food bag with one end slightly open for air circulation. It’s best if the cover never touches the sweet potato or any new growth.
• Place indoors in indirect light with consistent warmth (70-85°F or 21-29°C).
• Check every other day and water potting mix if drying out.

It’s the warmth and contact with moisture that causes the sweet potato to start producing fine white roots and buds which will become shoots (slips). These usually start appearing within a week or two.

In 4 to 6 weeks you will likely have a few inches of roots and shoots (slips). It’s also possible that your slips have already formed roots in the potting mix. If this is so, you can keep everything as-is until it’s time to transplant outdoors or transplant the slips to small individual pots.

Step 2 – Root the Slips

Rooting the Slips

There’s no firm rule about how big or long the slips should be at rooting time.

I always seem to have some sweet potatoes that are slow growing while others send up shoots that are several feet long within weeks.

You have two options: root the slips in water or potting mix.

If your slips already have roots, you can skip this step and transplant directly outdoors if the timing is right.

Supplies

• Sweet potato slips
• Small pots with drainage holes (3 to 4-inch wide, one pot for each slip)
  
  or
• Small water jars or a shallow pan of water
• Potting mix

Steps

To root in potting mix:

• Fill each pot with moist potting mix and gently press down to remove air pockets.
• Gently pinch, cut, or twist off each slip right where it joins the sweet potato.
  If your slips already have roots, plant them carefully to avoid breakage.
• Plant slip in pot with any roots below soil level and stems and leaves above soil level. Contact with the moist potting mix will cause root growth.
• Place pots indoors in indirect light with consistent warmth (70-85°F or 21-29°C).
• Water as needed, never allowing potting mix to dry out.

To root in jars:

• Place lower stems in water. Any foliage must be above water.
• Place jars indoors in indirect light with consistent warmth (70-85°F or 21-29°C).
• Change water every few days.

Advanced tip: Sweet potato slips can produce roots at every leaf node. If you have long stems with lots of leaves, you can cut them into multiple slips.

• Keeping track of the tip and base of the stem, make cuts between nodes. It’s good to have an inch of stem below the node and an inch or more above the node.
• Each piece is now a new slip. Bury at node level with the base end in the potting mix. Roots and leaves will eventually form.

Step 3 – Transplant the Slips

Transplanting Sweet Potato Slips Outdoors

If you started this process a few months before your average last frost, you should have rooted slips ready for transplanting outdoors by the time the risk of frost has passed.

While it’s nice to have at least an inch or more of established roots, if you got a late start, you can still transplant your slips directly outdoors or root them in pots outdoors.

It’s always smart to harden plants off first, allowing them to gradually adjust to outdoor conditions.

For growing the actual sweet potatoes, they can grow in-ground or in large, deep containers—the larger the better. I like container growing because it deters the mice and voles and I can move things around as needed but it can also mean smaller yields.

Steps

• Prepare your outdoor growing space and plant your slips.
  • Warmth, well-draining soil, and full sun are important.
  • Anticipate how much sweet potato vines can grow and sprawl. Like watermelons and pumpkins, they tend to head in the direction of the first sun of the day. 
• If growing in-ground, space your plants 18-inches apart.
• Water regularly until the plants are well-established with lots of new growth.

Harvest, Curing, & Storage

It’s harvest time in early fall when the foliage starts to yellow or the risk of frost is coming. Either way, you need them out of the ground before soil temperatures dip below 50°F or 10°C.

Sweet potatoes require curing before eating or storage. This is done by placing the tubers in a warm room (85°F or 29°C is ideal) with high (90%) relative humidity for a week or two. During this time, the starches convert to sugars.

After curing, the skins have hardened and you can gently brush off any dirt and store them in a cool, dark location (55°F or 12°C is ideal) with high humidity (80-85%) for several months.

Most of us do not have ideal conditions, and simply do the best we can. If it works, it works.

Frequently Asked Questions

Resources

Ebook

More Propagation Tips

• How to Propagate Sweet Potato Vines
• How to Grow a Peach (or Plum) Tree From the Pit
• How to Winter Sow Seeds (Milk Jug Method)

~Melissa the Empress of Dirt ♛