Sweet potato slips are tiny sweet potato sprouts that are planted to grow more sweet potatoes. Unlike regular potatoes, where the whole tuber is planted, sweet potatoes are grown from slips without planting the actual sweet potato.
Growing sweet potatoes isn’t quite the same as growing regular potatoes, and you can’t just plant whole sweet potatoes in the soil and expect a crop. Planting whole sweet potatoes is a recipe for mold and rot, as most of them will just spoil rather than grow.
In some locations with the perfect temperatures and soil conditions that might just work, and I did on occasion have a sweet potato plant thrive in my compost heap in California. That’s an exception though, as it is technically possible in hot dry locations. Still, that’s not exactly the best way in any case, as a single sweet potato is capable of growing into dozens of individual plants (rather than just one).
Generally, sweet potatoes are grown from what’s known as “sweet potato slips” which are rooted sprouts. Most people buy sweet potato slips by ordering them from seed companies in the spring (or early summer in cold locations). They can be expensive, and the tender young plants often don’t do well in shipping.
Growing your own sweet potato slips is easy, and not really any more difficult than growing your own seed starts. You’ll be able to get your plants started earlier, save a bit of money and have fun in the process.
A single sweet potato can grow literally dozens of sweet potato slips, enough to fill a large garden with plants. It doesn’t take much to get started, just a sprout-y old sweet potato from the pantry will do. (Or a fresh one that you can encourage to sprout, either way.)
When to Start Sweet Potato Slips
It takes about 2 weeks to sprout a sweet potato, in ideal conditions. Once you have sprouts, sweet potato slips take about 6 to 8 weeks to mature. Since they’re a warm-season crop, they are not planted outdoors until 2 weeks after the last frost.
That means you’ll need to start about 6 to 8 weeks before the last frost in your area to have slips ready on time.
If we want to grow sweet potatoes the next year (and haven’t grown any the previous year), we’ll plan ahead. We generally buy a crate of organic sweet potatoes when they go on sale around Thanksgiving or just before Christmas. It’s one of the ways we save money on groceries each year, since they’re usually half price at that time of year.
The sweet potatoes will keep most of the winter at room temperature, but by late winter they’re starting to sprout. It’s usually right around the perfect time, roughly 2 months before our last frost.
Sprouting Sweet Potatoes
The first step in growing sweet potato slips is sprouting sweet potatoes. If you have organic sweet potatoes that aren’t treated with germination inhibiting chemicals, this often happens on their own in storage.
Make sure you buy sweet potatoes well ahead of time, and store them for 6 to 8 weeks in a room-temperature location (not cold storage).
Unlike potatoes, which are stored in cool root cellar environments, sweet potatoes are a hot climate crop that likes room temperature storage. If you have dry winters, that works well and they’ll keep for many months without sprouting.
In our humid Vermont climate, they start to sprout on their own in late winter. Once I see the little sprouts I’ll pull them out of the pantry and set them on a sunny windowsill. The sprouts will be “bleached” since they’re stored without light, but they’ll green up quickly in the light.
Tips for Getting Sweet Potatoes to Sprout
You may have trouble sprouting sweet potatoes if you live in a particularly cool, dry climate. They need warmth and humidity to initiate growth.
A warm, active kitchen is a great place to encourage sprouting, since the extra humidity from cooking will help encourage them to sprout. Bathrooms are good spots for a similar reason.
You can also place the sweet potato in water, either a glass with the bottom tip just touching the liquid, or in a tray of water. I’ve had good luck placing the potatoes on seed starting flats without holes and adding just a bit of water. I then put those trays onto our seedling heat mats, which creates the perfect warm/humid conditions for sprouting.
A bit of sunlight also helps, especially once the sprouts start to form.
Growing Sweet Potato Slips
Once your sweet potatoes have sprouted, they need to be rooted before they’re actually full “sweet potato slips.”
Allow the sprouts to grow to about 2” (5 cm) long, and then carefully break them off where they attach to the sweet potato. Place that sprout into a cup of water and set it on a warm sunny windowsill.
Change the water every few days, and watch for roots. You should see roots in 1-2 weeks.
If the sweet potato is still firm and not beginning to spoil, you can keep it and encourage more sprouts. You should be able to get 6 to 20 slips from a single sweet potato, depending on size.
If the sweet potato starts to get squishy or spoiled, then it’s time to put it into the compost. Break off any sprouts, no matter how small, and try to root those without the sweet potato. Once the potato gets soft, then things get messy. It’s time to toss it even if the sprouts are quite small.
A single small cup can hold many sweet potato sprouts, just make sure it’s relatively shallow, or keep the sprouts supported. You only want the very bottom of each sprout in the water. If they’re too deep, they’re liable to mold rather than root.
Keep the leaves, and most of the stem, out of the cup and in sunlight.
Planting Sweet Potato Slips
Once your sweet potato slips have several strong roots each, it’s time to get them in the soil.
I’ve you’ve started out late this season, and outdoor temperatures are already warm, you can just plant them outdoors. Be sure that you’re at least 2 weeks past your last frost date. We’re talking no chill in the air here, and warm sunny days. In Vermont, that’s not until mid-June but it’s in February in California…so decide based on your location.
While you can just plant them out, that’s not actually the best option. Ideally, you’ve started your sweet potato slips a bit early, and you still have about 4 to 8 weeks before outdoor planting time. This will give your sweet potato slips time to fully mature into small sweet potato plants indoors, which will give them a headstart on the season.
It’s kind of like tomato starts. Sure, you could plant them out as soon as they germinate (at 2” tall), but they’ll be better off if you let them mature into small plants first.
In the meantime, the rooted sweet potato slips need soil and nutrients, as well as light. We plant each one in a 4” pot with good quality potting soil, and place them on our seed starting rack with grow lights. Lacking grow lights, a sunny windowsill will work too.
If you notice yellowing leaves while they’re developing, a liquid seaweed fertilizer will help keep them healthy and nourished until they reach garden soil. Amending their potting soil with compost also helps.
After a few weeks, the sweet potato slips will have grown into good-sized plants and they’ll be ready to plant outdoors. At this point, they’ll be starting to vine across each other and they’ll be happy for more space.
It can be helpful to harden off your young sweet potato plants before planting, especially if they haven’t been exposed to enough light indoors. Bring them outside for a few hours each day in the week leading up to their planting time to help acclimate them to bright sunlight.
When planting outdoors, be sure to choose a spot with full sun and plenty of soil nutrients. Since they like warm soil temperatures, we tend to plant them in raised beds to help balance out our cool summer temps.
In warmer locations, right in the ground is perfectly fine, just be sure your soil is amended and has lots of organic matter.
Harvest sweet potatoes after the leaves start to yellow in the fall, before the first frost in your area. After harvest, store the potatoes in high heat (85 to 90 degrees F) for about 15 days to help them develop tough skins for storage.
Store sweet potatoes at room temperature, around 70 degrees (not in a root cellar). If you don’t have a good place to store them, then canning sweet potatoes is a great way to preserve them right on the pantry shelf.
Sweet Potato Greens
Growing sweet potato slips is actually fun (and worth it) even if you don’t have any garden space. While homegrown sweet potatoes are delicious, I think the real treat is sweet potato greens.
While sweet potatoes, even high-quality organic heirloom sweet potatoes, can be purchased in the store or farmers market, there’s almost nowhere you can buy sweet potato greens.
Unlike regular potatoes where the plants are toxic, every part of the sweet potato plant is edible.
Many people grow them as houseplants, and they do make beautiful vines. You can snip off the greens periodically to add to salads or stir-fries.
If grown indoors on a sunny windowsill the plant will thrive even through the winter months, and I’ve harvested fresh sweet potato greens indoors in January even here in the north country. We just keep the plant in a warm spot (near-ish the woodstove) and make sure it’s near a south-facing window.
I always start a few extra sweet potato slips to keep indoors for greens.
They’ll actually produce sweet potatoes too, and over time they’ll consume all the soil in the pot and replace it with fresh sweet potatoes (even indoors). We had that happen once, and I went to repot our indoor sweet potato plant to find that there was only a scraping of soil on top and a solid mass of sweet potatoes below.
The picture below is a container-grown sweet potato after about 6 months. We let this one grow outdoors in the summer months and I’m just about to bring it indoors for the winter. I’ve taken it out of the pot, and I’ll break off that sweet potato for our kitchen before I re-pot it for the winter.
It’ll make more sweet potatoes, of course, even indoors. My real goal with this little one is the greens, and they’ll be plenty of those all winter long.
If you lack garden space, sweet potatoes do really well in containers too (as you can see). And when we’re short on garden beds I’ll plant them in large nursery pots (leftover from perennials) or in large grow sacks.
Something like a 5-gallon bucket with holes drilled in the bottom will work, but a large 20 gallon grow bag is even better. You’ll harvest plenty of sweet potatoes from those without any garden space.
Looking for more growing guides to keep your garden lush and productive this season?
- Growing Everbearing Strawberries
- Growing Strawberries from Seed
- How to Plant Asparagus
- Growing Asparagus from Seed