The sweet potato is a warm-season, spreading vegetable of tropical origin. It is a good choice for a garden because it is easy to grow, is drought- and heat-tolerant, and has few pests or diseases. The sweet potato is also very nutritious and low in calories.
Planting, Growing, and Harvesting Sweet Potatoes
- Sweet potatoes are grown from slips, which are sprouts that are grown from stored sweet potatoes. You can buy slips from garden centers, nurseries, or local farmers.
- You can also grow your own slips to plant in the spring. In November (this is when the best of the new harvest will be out), go to your supermarket and look for unblemished and uncracked medium sweet potatoes. One potato should yield about 12 plants.
- Store these potatoes in a well-lit room with a temperature between 65° and 70°F. Keep them there until about 90 days before the last spring frost date. They will then need to be embedded in soil for 90 days and kept continuously warm and moist.
- Use a 1-½ gallon pot for every two potatoes. Remember to poke drainage holes in the bottom of the pot and fill it with 3 inches of mulch followed by garden or potting soil. Plant the potatoes in the pot at a 45° angle so that the sprouts will grow above the soil. When the slips are 6 to 12 inches tall, you can plant them outdoors as long as all danger of frost has passed.
- After you have grown your own slips or bought them, till the area of the garden you will be using to a depth of 8 to 10 inches. Create raised beds 6 to 8 inches tall and about 12 inches wide. Use fertile, well-drained soil.
- Plant the slips 12 to 18 inches apart in the bed, after the last spring frost date. Plant the slips deep enough to cover the roots and about ½ inch of the stem. Water the slips with a starter solution that is high in phosphorous, then water generously for a few days to make sure that the plants root well.
- Side-dress the potatoes 3 to 4 weeks after transplanting with 3 pounds of 5-10-10 fertilizer per 100 feet of row. If you have sandy soil, use 5 pounds.
- Hoe the beds occasionally to keep weeds down. Remember to reshape the beds with soil or mulch.
- For good harvests, do not prune the vines, because they should be vigorous.
- Remember to keep the potatoes watered. Deep watering in hot, dry periods will help to increase yields, although if you are planning to store some of the potatoes, do not give the plants extra water late in the season.
- You can start digging up the potatoes as soon as they are big enough for a meal. Often, this is 3 to 4 months from when you planted the slips.
- Usually, sweet potatoes are ready to harvest when the leaves and ends of the vines have started turning to yellow, but you can leave them in the ground up until the fall frost.
- Since the roots spread 4 to 6 inches deep in the soil, a spade fork is useful when digging up the potatoes. Loosen the soil around the plant (18-inch diameter) so you do not injure the tubers. It’s fine to cut some of the vines away.
- Pull up the primary crown of the plant and use your hands to dig up the potatoes. Handle the potatoes carefully because they bruise easily.
- After digging up the potatoes, shake off any excess dirt but no not wash the roots.
- You must cure sweet potatoes or they will not have that delicious, sweet taste. Curing the potatoes allows a second skin to form over scratches and bruises that occur when digging up the potatoes. To cure, keep the roots in a warm place (about 80°F) at high humidity (about 90%) for 10 to 14 days. A table outside in a shady spot works well. For best curing, make sure that the potatoes are not touching one another.
- After curing, throw out any bruised potatoes, and then wrap each one in newspaper and pack them carefully in a wooden box or basket. Store the sweet potatoes in a root cellar, basement, or other place with a temperature of at least 55°F.
- If stored at a temperature range of 55° to 60°F with high humidity, the roots should last for about 6 months. When removing the potatoes from storage, remember to be gentle; do not dig around or else you will bruise the potatoes.
- ‘Centennial’, which is one of the most popular types of sweet potato. It is carrot-color and has a good storage life. It is also a good producer for northern growers.
- ‘Jewel’, which is copper-color and has good disease resistance. It also has a good storage life.
- ‘Bunch Porto Rico’, which is a good choice for gardens with limited space. It is copper-color and very flavorful.
- ‘Stokes’ purple sweet potatoes offer a vibrant purple color and are full of extra health benefits.
Wit & Wisdom
Sweet potatoes will retain their color if cooked with a slice of lemon.
Sweet potatoes are a very healthy vegetable, and they provide many benefits. Learn more about why you should eat sweet potatoes.
To the cook, sweet potatoes are easier than pie (or sweet potato pie!).
- They can simply be scrubbed, poked with a fork in a few places, and baked at 400°F for 35 minutes to one hour, until they give a bit when you squeeze them in your pot-holder-protected hand.
- In the microwave, a whole sweet potato baked on high should be ready in 4 to 6 minutes. It may still feel firm when done; let it stand 5 minutes to soften.
- Sweet potatoes can also be steamed whole, cleaned and unpeeled, for about 40 minutes or until tender, or cooked whole, cleaned and unpeeled, in boiling salted water for about 35 minutes. (Boiling reduces the flavor considerably.)
- Immerse cut raw sweet potatoes in water until you’re ready to cook them; they will darken otherwise.
As a general rule, don’t substitute sweet potatoes for regular potatoes in recipes; the two aren’t related. Sweet potatoes don’t hold together the way potatoes do, and their strong flavor can overwhelm a dish meant for a milder potato taste. But they make a fine substitute for pumpkin, especially in desserts.