Sweet potatoes come in two general forms: vegetable varieties bred for their edible roots and varieties bred for their ornamental trailing vines. Both types belong to the Ipomoea batata species, a tender perennial normally grown as an annual. And both ornamental and edible varieties are quite easy to grow in pots.
Both types grow best in sunny conditions. If you want to grow edible tubers, it will take roughly 100 to 140 days depending on the variety. In some parts of the country, that means starting your plants about six to 12 weeks before your area's projected last frost date in the spring to have a long enough growing season. Sweet potatoes are widely available for sale as small container plants in the spring. But they are also easy to grow yourself by sprouting "slips" from pieces of the tubers.
Tools and Supplies You Will Need
- Sweet potato tubers
- Glass containers for each tuber
- Shallow dish
- Potting soil
- Planting containers
Prepare the Tubers
To get started, look for firm sweet potatoes without any major bad spots. It's better if they haven't been refrigerated. Use a sharp knife to cut the tubers into pieces just slightly smaller than the opening on your glass container.
Then, locate the middle of each tuber piece, and insert three or more toothpicks into it; they should go about 1/2 to 1 inch into the tuber. Space the toothpicks evenly around the circumference of the tuber. If the tuber is too hard, you can drive a small hole with a thin nail and then stick the toothpick into it.
Position the Tubers in Water
Place each tuber so that the toothpicks rest on the edge of a jar with the pointed end of the tuber facing down. Fill the jar with enough water to cover the bottom half of the tuber. Then, put the jar on a sunny windowsill, and change the water every couple of days. Make sure to keep the bottom of the tuber submerged in water.
It can take a few weeks or even a month before you see green growth sprouting from the top of the tuber. The individual shoots that will sprout from the tuber are known as "slips," and these will be what you use to create new sweet potato plants.
If your tap water is heavy with chlorine and other additives, it can prevent the tuber from sprouting. If the tubers are not sprouting, replace the tap water with distilled water.
Separate the Slips
Once the sweet potato tuber has sprouted, carefully separate each slip from the tuber by gently twisting it. There might already be a rudimentary root structure attached to the slip.
Lay each slip in a shallow dish with the bottom of the stem submerged in water and the leaves hanging over the edge of the bowl. New roots will begin growing from the bottom of the slip within a few days.
When the new roots are about 1 inch long, the slips can be planted in potting soil. Discard any slip that is wilting or that hasn't produced any roots; these won't be viable.
Plant the Slips in Containers
If you want to grow your sweet potato vines as decorative plants, find a small 3- or 4-inch seedling pot with good drainage. Once your plants have begun to grow robustly indoors, they will be ready to transfer to large containers mixed with other plants if you wish. If you are growing edible sweet potatoes, you'll need a large container with drainage to allow them adequate room to grow. Or if you plan to plant the edible sweet potatoes in the ground, then the slips also can be started in seedling pots.
To plant, fill a container with high-quality potting soil until the soil reaches about 1 inch below the rim. Don't firmly compress the soil; the tubers need loose soil to grow large. Mix a slow-release fertilizer into your potting soil if it doesn't contain fertilizer already. Then, make a hole in the center of the soil, deep enough to cover the roots of the slip. Gently put one or two slips into the hole, and pat the soil firm around them. Make sure there are no air pockets near the roots. Water thoroughly.
Put your pot in a sunny indoor spot, and keep the soil moist but not soggy. To test moisture levels, stick your finger into the soil up to the second knuckle. If the soil feels dry, add water. If it's moist at your fingertip, wait until it's dry.
Move the Plants Outdoors
Sweet potatoes like warm weather, so make sure all danger of frost has passed before you put your new plants outside. It's best if temperatures have consistently been at least 65 degrees Fahrenheit. It also helps to harden off the new plants by acclimating them gradually to the outdoors before putting them into their permanent locations.
You can harvest sweet potatoes at any stage, and they will be edible. Check your variety for the specific number of days it takes to fully mature. In any case, sweet potatoes should be harvested before the first frost in the fall for best edibility. To get the most flavor from your sweet potatoes and to extend their shelf life, cure them in a warm, dry place for 10 to 14 days before eating.