Sweet potatoes are nutritious and delicious root vegetables that are easy to grow in beds or containers.  Root vegetables like carrots, turnips, and beets are grown from seed, but sweet potatoes are grown from slips.  Slips are short vines that have sprouted from a mature sweet potato. You can purchase slips online from seed companies or sometimes from local plant nurseries, or you can pick up an organic sweet potato from the grocery store and grow your own.  (It is best to use organic sweet potatoes because, more than likely, they have not been sprayed with a sprout-retarding chemical like non-organic potatoes often are.) Growing your own slips is easy to do and a fun way to get kids interested in gardening. In this post, you will learn how to grow slips using two different methods, when to start the process, and how to plant them once they are ready.

When to Start Growing Sweet Potato Slips

Sweet potatoes require a long growing season of about 90 to 120 days, depending on the variety, so you will need to start the slip-growing process about six weeks before the last expected frost date in the spring.  (Check out this link to determine the last expected frost date for your area.)  Regardless of which of the two methods you use, each sweet potato will produce up to about a dozen slips.

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Jar of Water Method

Depending on the size of the potato, you will need a medium to large sized jar or other container that is large enough to hold the sweet potato.  A quart mason jar works well, and the clear glass allows you to easily observe root development. 

Place the rooting end of the potato, which is usually the smaller, more tapered, or pointy end, into the jar.  Insert three or four toothpicks into the potato to suspend it so that only half of the potato is inside the jar.  Fill the jar with water. Over time, the water in the jar will decrease due to absorption and evaporation, so be sure to maintain the water level by adding more water as needed.  Replace the water in the jar every week or so.  You should see roots start to develop in a few weeks.

The sweet potato will need warmth and light in order for it to develop roots and then sprouts.  Ideally, this is achieved by placing the jar on top of a heat mat situated under a grow light.  Alternatively, you can place the jar on a sunny window sill where it will get both light and warmth, but the process will take longer.  Once the roots start to develop, it will take about 3 or 4 weeks for sprouts to emerge on the top portion of the potato.  As the sprouts develop, they will begin to look like vines or slips.  When the slips have grown to at least 6 inches (15 cm) or more, cut or break them off at the base.

The slips now need to develop their own roots, so they can be planted in the soil.  To do this, insert the slips into a jar of water, removing any leaves that fall below the water’s surface.  Place the jar on a heat mat under a grow light or in a sunny window.  It will take about a month for the slips to develop a strong root system.  When the roots are about 4 inches (10 cm) long and the chance of frost has long passed, the slips can be planted in the garden.  (See more specific planting directions below.)

Soil and Shallow Pan Method

While the jar of water method is more familiar, there is a faster way to grow slips!  Take an aluminum baking pan that is about 3 inches (8 cm) deep.  An aluminum cake or lasagna pan from the dollar store works great!  Punch several small holes in the bottom of the pan for drainage. Place the pan inside the pan’s plastic lid if it comes with one, or you can use another shallow pan to act as a reservoir to catch the draining water.

Fill the pan with about 2.5 to 3 inches (6 to 8 cm) of good a quality potting mix.  (Check out this article if you want to know why it’s best to us potting mix.)  Place a couple of organic sweet potatoes in the soil so that they are laying horizontally and not touching one another.  Press them into the soil so that they are halfway below the soil’s surface.  Water the soil so that it is damp but not soggy.

Place the pan with the drain catchment (plastic lid or additional pan) on a heat mat situated under a grow light.  You can also place it in a sunny window, but the process will take longer.  Keep the soil moist but not soggy as this may attract fungus gnats.  Sprouts will begin to emerge in about two weeks.

In about 4 to 6 weeks, when the slips are at least 6 inches (15 cm) or more, remove them from the sweet potato and place them in a jar of water, removing any leaves that are below the water’s surface.  Maintain the water level in the jar and replace it all every week or so.  In about a week or two, the slips will develop roots. Once the roots are about 3 or 4 inches (8 to 10 cm) long, they are ready to be planted in your garden.

Using either method, if the leaves on the slips develop bumps or blisters that look like salt crystals, it is more than likely a condition known as plant edema.  You can learn more about it in this helpful article.

How to Plant Rooted Slips

Once the slips have developed roots that are about 3 or 4 inches (8 to 10 cm) long, they are ready to be planted in the garden.   

Sweet potatoes do not like cold weather, so wait until the danger of frost has long passed and the soil temperature is 65 °F (18 °C).  Regardless of which method you used to grow slips, plant them in the soil at a depth of about 4 to 6 inches (10 to 15 cm).  If growing in beds, plant the slips about 12 to 18 inches (30 to 46 cm) apart.  Or plant two to three slips in a 10 gallon (38 liters) container or grow bag (fabric pot).  Water well and keep the soil moist but not soggy until the roots are established.  During the growing season, water with a liquid fertilizer that is higher in phosphorus than nitrogen.  You want the plant to put more energy into the roots and not into the leaves.  This is the one I use.

Growing sweet potatoes from the slips you grew is a fun, easy, and rewarding experience!  You can learn more about how to grow sweet potatoes, including how to combat pests and diseases, which varieties to grow, how to cure them after the harvest, and much more in this helpful article!

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