Have you ever left a sweet potato out too long? As the days passed, you probably saw it begin to sprout, and wondered if you could plant it. I was wondering the same thing myself. As it turns out, the answer is not quite that simple.
So, can you plant a sweet potato that has sprouted? No, you should not plant an entire sweet potato that has sprouted. However, you can plant the “slips” (rooted sprouts) that grow out from a sprouted sweet potato. Given the proper care, slips will grow into plants that can produce sweet potatoes for you.
Let’s take a closer look at sweet potatoes and why they sprout. We’ll also talk about how to plant sweet potato slips, how to care for sweet potato plants, and how to harvest and store them at the end of the season.
Can You Plant a Sweet Potato That Has Sprouted?
No, you should not plant an entire sweet potato that has sprouted. Instead, you should wait for the sprouted parts to grow longer and develop roots. Eventually, they will be ready for planting in a container, raised bed, or garden.
It is worth noting that you can plant a potato (or parts of a potato) that has sprouted. For more information, check out my article on planting sprouted potatoes.
Why Do Sweet Potatoes Sprout?
Like all plants, sweet potatoes have a goal of reproduction – they want to create a new generation of sweet potato plants. Even in difficult circumstances, sweet potatoes will attempt to do just that.
Sweet potatoes contain plenty of nutrients and starches in their flesh, so they have the resources available to produce sprouts. As long as they are warm enough (and not damaged by cold), sweet potatoes will begin to sprout.
Given the right conditions, the sprouts will eventually root and start growing into a new plant. Sweet potatoes will break dormancy and begin to sprout with high temperature and humidity (this tells them that the season for growth is approaching, and it is time to reproduce).
The sweet potato is a member of the morning glory family, and is native to tropical regions of America. As such, they prefer warm temperatures, and will be damaged by temperatures of 50 degrees Fahrenheit (10 degrees Celsius) or lower.
For more information, check out this article on sweet potatoes from Wikipedia.
To encourage your sweet potatoes to sprout, keep temperatures warm, at 75 to 85 degrees Fahrenheit (23.9 to 29.4 degrees Celsius). Also, keep the humidity level high (80% to 95%).
One good way to do this is by using a humidity dome (often used for seed germination). For more information, check out my article on humidity domes.
How Long Do Sweet Potatoes Take to Sprout?
It will take about two weeks for sweet potatoes to sprout, given the right conditions (temperature and humidity). After that, the sprouts should begin to root in 10 days.
You can plant sweet potato slips (rooted sprouts) in the garden, unless the weather is cold. In that case, you can plant them in a container with potting soil until outdoor conditions improve.
For more information, check out this article on starting sweet potatoes from Clemson University.
How to Sprout Sweet Potatoes
The Clemson article above suggests suspending sweet potatoes in water to encourage them to start sprouting. This method will work, but by starting the slips in water, you are denying them the nutrients found in soil.
If you have the space available, consider sprouting your sweet potatoes in soil instead.
First, find a suitable place to sprout your sweet potatoes. This should be somewhere you can keep the soil warm, at 75 to 85 degrees Fahrenheit (23.9 to 29.4 degrees Celsius). One way is to place a tray with soil on top of a seedling heat mat.
Next, choose sweet potatoes for sprouting. Remember that smaller sweet potatoes are better for sprouting (besides, wouldn’t you rather eat the larger ones?).
Once you have chosen sweet potatoes for sprouting, put them in the soil, with the sprouting end up. If you are not sure which is the sprouting end, lay the sweet potatoes sideways on top of the soil. Once they begin sprouting, you can move them accordingly (so that the sprouts are facing up).
While you wait for the sweet potatoes to sprout, keep the soil moist. You can spray the soil frequently with a water bottle, or use a humidity dome to trap moisture in the air around the sweet potatoes.
How to Plant Sprouted Sweet Potatoes
After your sweet potatoes form sprouts, and the sprouts form roots, you have slips that are ready to plant (you can snap them off from the sweet potato close to where they emerged). However, just because the slips are ready does not mean the weather is ready to cooperate!
You will need to wait for ideal conditions outdoors before planting your slips. In the meantime, you can plant them in potting soil inside containers to give them a bit of a head start until you can transplant them outdoors.
Wait for the Right Weather Conditions to Plant Sweet Potato Slips
Sweet potatoes are a warm-weather crop – if you plant them too early, the cold will kill them. The University of Maryland Extension suggests waiting until soil temperatures are at least 65 degrees Fahrenheit (18.3 degrees Celsius) before planting your sweet potato slips.
At the very least, you should wait until after any danger of frost has passed. The Old Farmer’s Almanac suggests waiting until after the last spring frost date to plant your sweet potato slips.
To find the last spring frost date for your area, check out the frost date calculator from the Old Farmer’s Almanac website.
If you live in a colder northern region, you may still be able to grow sweet potatoes. However, you may need to extend the season in both the spring and fall.
You can do this by using clear or black plastic mulch to increase soil temperature. An added benefit is that this will keep the soil moist.
You can also take the time to “harden off” your sweet potato slips before transplanting them outside for good. For more information, check out my article on how to harden off your seedlings (young plants).
Choose and Prepare a Garden Site for Sweet Potatoes
Given the right conditions, your sweet potato slips will grow into vigorous plants that will produce plenty of sweet potatoes for you. That leads to an important question – what are the right conditions for growing sweet potatoes?
First, identify areas of your garden that get 8 or more hours of full fun per day, with partial shade during the rest of the day. Avoid areas with full shade, since this will inhibit the growth of sweet potato plants.
Avoid planting your sweet potato slips near tall plants, such as tomatoes or pole beans. Otherwise, these taller plants will shade the sweet potatoes too much as the season goes on.
If you must, plant the sweet potatoes on the south side of taller plants so they will get more sun. Otherwise, plant sweet potatoes in their own area where they can get enough sunlight.
Next, identify areas of your garden that have good soil for growing sweet potatoes. Ideally, the soil will be light and sandy (rather than heavy or clay), with a pH from 5.5 to 6.5 (slightly acidic).
To find out your soil pH, you can use a home test kit, or send it away to your local agricultural extension for testing. To learn more, check out my article on how to test your soil.
You can use fertilizer if your soil is poor, but avoid using too much nitrogen, since this will lead to plants with lots of vines and leaves, but very little in terms of sweet potatoes.
For more information, check out my article on low-nitrogen fertilizer.
When your sweet potato slips are ready for transplant, dig a ditch 3 to 4 inches (8 to 10 centimeters) deep. Plant the slips 8 to 12 inches (20 to 30 centimeters) apart.
Leave 3 feet (0.9 meters) between rows. This gives you enough space for watering, fertilizing, weeding, inspecting, and harvesting your plants as they grow.
Watering Sweet Potato Plants
Sweet potatoes are able to tolerate both heat and drought once they are established. However, plants are vulnerable to drought during transplant and early development.
Water your sweet potatoes in the morning to give them time to dry out during the day. The University of Georgia suggests you stop watering 3 to 4 weeks before harvest to prevent splitting of the sweet potatoes.
When the top inch or so of soil above the sweet potatoes is dry, give them water. There is no rule for when this needs to be done.
It will depend on temperature, humidity, your soil, and how much water the sweet potatoes use. Your best bet is to check the soil with your fingers each day to see if it is dry.
If you have trouble with dry soil, check out my article on how to treat dry soil.
Harvesting and Storing Sweet Potatoes
You’ve sprouted the sweet potatoes, planted the slips, and cared for the plants throughout the summer. Now it’s time to harvest and store the sweet potatoes!
When to Harvest Sweet Potatoes
Sweet potatoes mature in 85 to 120 days (3 to 4 months) after planting slips. Make sure to harvest them well before the first frost in your area (watch the calendar, and also the weather forecast!)
If your sweet potatoes are exposed to cold, they will become hard inside, and they will not soften up no matter how much you cook them.
If you are not sure whether it is time to harvest yet, you can dig up a few sweet potatoes to check on the size of the tubers (roots). According to Clemson University, you can harvest when 30% of the roots are at least 3.5 inches in diameter.
So, if 1 out of the 3 sweet potatoes you dug up is at least 3.5 inches in diameter, then you are ready to harvest!
How to Harvest Sweet Potatoes
When you harvest sweet potatoes, cut the vines first and remove them. You can put them in your compost pile if you have one!
When digging for sweet potatoes, use a small tool (or your hands) to dig. Handle the sweet potatoes gently. Otherwise, you will damage the skin or bruise the flesh, and they will not keep as long in storage.
Brush off the dirt (you can use your hands or an old brush you might have lying around). Just don’t wash them, since getting them wet will reduce storage life.
According to the University of New Hampshire Extension, you should wait a few weeks after harvesting your sweet potatoes before eating them for best results. That way, some of the starch will turn to sugar, making for a delicious meal when baked or mashed!
How Many Sweet Potatoes per Plant?
One plant can produce several sweet potatoes. The Iowa State University Extension suggests that 50 plants will yield about one bushel (50 pounds) of sweet potatoes, or 1 pound per plant.
A medium sweet potato weighs 4 ounces on average, so that means about 4 medium sweet potatoes per plant. It all depends on the variety, the climate, the soil, and the care you give your plants!
How to Store Sweet Potatoes
Make sure to store sweet potatoes in a place that stays at 60 degrees Fahrenheit (15.6 degrees Celsius) or above. Otherwise, they will become stringy and impossible to eat. Note: this also means that you should not refrigerate them (at least not until they are cooked!)
Potential Sweet Potato Problems
There are a few problems to look out for when planting sprouted sweet potatoes to grow your own produce.
Sprout Inhibitors on Sweet Potatoes
Many store-bought sweet potatoes are treated with sprout inhibitors. These are simply chemicals that discourage the sweet potatoes from sprouting.
This is helpful for increasing the shelf life of sweet potatoes in grocery stores. However, it will make it more difficult for you to sprout your sweet potatoes.
Fusarium root rot is one disease that may affect your sweet potato plants. It is caused by the fungus Fusarium solani, which can affect many different plants. In sweet potatoes, fusarium root rot appears as brown concentric rings.
To avoid fusarium root rot, avoid harvesting when soil is cool and damp, or when the soil is too dry. Since fusarium root rot is caused by a fungus, high humidity levels will also make it worse. Also, use crop rotation (avoid planting the same crop in the same place every year).
One common insect pest of sweet potatoes is the root-knot nematode, which also affects other garden plants.
Animal pests of sweet potatoes include deer, rabbits, squirrels, and voles.
Hopefully, this article gave you enough information on how to plant slips from sprouted sweet potatoes, how to care for the plants, and how to harvest and store your bounty. You should also have enough information to avoid some of the more common problems with growing sweet potatoes.
I hope that you found the article helpful – if so, please share it with someone who can use the information.