Texans who want to grow their own sweet potatoes should consider themselves lucky because our state is an ideal place to grow these root vegetables. In this article and accompanying video, you’ll learn the organic way to grow them without applying chemical pesticides or herbicides that can harm you and your family. We’ll also share a few of the many recipes that make sweet potatoes such a popular vegetable to grow.
A Beautiful Tropical Vine
In tropical Central America, where it originates, the sweet potato is a perennial, but it’s been adapted to grow in many parts of the U.S. as a warm-season annual. Fortunately for us, Texas provides one of the best sweet potato growing climates in America. Our hot summer days and equally warm nights with medium to high humidity provide make for excellent growing conditions. For that reason, Texas is the fifth largest producer of sweet potatoes in the United States.
The versatile sweet potato (Ipomoea batatas) is a completely different genus and species from the Idaho or Russet potato (Solanum tuberosum). Solanum tuberosums are members of the nightshade family and so are related to tomatoes. Sweet potatoes, on the other hand, are related to morning glories (Ipomoea tricolor).
Edible varieties should not be confused with the ornamental sweet potato vine. Although they are close relatives, the ornamental version is tough, tasteless, and non-flowering, best grown as ground cover or in hanging baskets and containers. Edible types not only grow amazingly large and sweet tasting roots, but also produce striking white flowers with purple centers similar to their morning glory cousins.
Many people also confuse sweet potatoes with yams. Although their names are often used interchangeably, they are not related. Yams belong to the Dioscorea alata family.
Health Benefits
Sweet potatoes also provide many health benefits. Besides being an excellent source of beta-carotene, which is converted by the body into vitamin A, they are high in vitamin C and antioxidants. Although sweet in flavor, they have a low glycemic value, which prevents spikes in blood sugar. They are also high in fiber, which helps make you feel full and so can help with weight loss.
Varieties suitable for North Texas
Typically the sweet potatoes sold in grocery stores are orange in color, but they can also be white, yellow, or even purple. Orange varieties are exceptionally high in beta-carotene, which is important for eye health, while purple varieties are most rich in antioxidants that help reduce inflammation and boost your immune system.
There are hundreds of sweet potato varieties available for growing. Flesh color is just one factor in choosing which ones you want to plant. Another consideration is the number of days to maturity — that is, how long it takes to grow from planting day until harvest time. This is important because sweet potatoes are very slow growing and need a long, warm growing season free of any frost.
And of course, some types are better suited to our specific growing conditions. Some of the best choices for North Texas are:
‘Beauregard': Pale reddish or light purple skin with dark orange flesh. Typically 100 days to harvest.
'Bush Porto Rico': A more compact vine, the Porto Rico has copper colored skin and orange flesh. It requires 110 days to reach maturity but it offers larger yields, making it a great one for smaller spaces.
'Georgia Jet': A faster growing variety, it typically reaches maturity in about 90 days. Reddish skin and orange flesh.
Watch Episode 9 of our Spring 2021 Vegetable Gardening Series: How to Grow Sweet Potatoes.
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When To Plant
As mentioned earlier, sweet potatoes are slow growing and need four full months of warm weather to grow, with some varieties needing as long as 110 days to reach maturity. They are well adapted to our summers, being both heat and drought tolerant, so if you forget to water them for a few days, they should easily recover. Not so with cold. Your soil temperature needs to be at least 65°F — and at least 155 days before soil temperatures drop below 55°F soil temperature in the fall. They can also tolerate light frosts as long as the soil temperature stays above 55°.
In North Texas, this means sweet potatoes are usually planted in mid to late spring — usually in April or May after any chance of frost has passed. Your soil temperature needs to be at least 65°F — and at least 155 days before soil temperatures drop below 55°F soil temperature in the fall. Sweet potatoes are extremely heat tolerant. They can also tolerate light frosts as long as the soil temperature stays above 55°.
Time of Day
While many gardeners like to work early in the day when it's cool, sweet potatoes are late risers and prefer to be planted in the late afternoon around sunset.
Preparation
Proper preparation is another important factor in growing sweet potatoes. In this section, we walk you through the necessary steps to ensure success.
Most vegetables are grown from either seeds or from “transplants” (young seedlings with developed roots that are ready to be transferred into the ground). Sweet potatoes are different. Instead, they are grown from “slips” — essentially cuttings taken from a mature sweet potato and placed in water until they’ve developed roots that are at least 3 inches long.
Marshall Grain Co. sells slips in bunches of 25. These are ready to plant at the time of purchase and do not need additional root development beforehand.
If there is to be a delay in planting, keep the roots of your slips moist by suspending them in a jar of water or wrap them in sawdust, moss, burlap, or something similar. They should be kept in a sunny location out of the direct sun and wind.
Don’t be concerned if they look or smell bad. Your plants will succeed even if they are yellow, slimy, and have a strong odor.
Site Selection & Soil Preparation
Sweet potatoes can generally be planted in full sun and, as mentioned, are heat tolerant, however, since summer afternoons in North Texas can be extremely hot, it wouldn’t hurt to provide them with some afternoon shade.
They can be planted directly in the ground or in raised beds. Vining varieties need lots of room to spread. Their vines can extend to 20 feet and tubers average 4 to 6 inches long.
More compact bush varieties can be grown in large, deep pots.
Sweet potatoes need loose soil to allow the tuberous roots to form properly. Hard, compacted soil will keep the roots from fully developing. They also need excellent drainage to prevent rotting. Ideally, your soil should be coarsely textured and well-drained but high in organic matter that is crumbly and granular. However, sandier soil is preferable to dense, clay soil.
Sweet potatoes also prefer their soil to have a slightly acidic pH of 5 to 7.5.
Before you plant them, you should create a mounded row 8 to 12 inches high. The higher the row, the more space there will be for the potato to develop. Plant slips about 12 to 18 inches apart with 3 to 4 feet between rows. The vines will spread and fill in, so give them plenty of room.
Once planted, the vines will put down new roots wherever they touch the ground, so just a few plants can produce a very generous harvest.
When you are ready to plant, dig a small hole in your mound deep enough for the roots to be fully covered and gently place the slip into the hole.
Note: Always plant in wet soil. Never place roots in a dry planting hole.
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Fertilization
Sweet potatoes don’t need very much fertilization, especially if they are planted in loose, well-composted soil. Most areas of Texas have enough phosphorus and potassium in the soil already. A single balanced fertilization at planting time should be all that’s needed for the course of the season.
Work in some compost or an evenly balanced fertilizer (such as Espoma Tomato-tone or Espoma Bio-Starter Plus) to a depth of 8 inches. Alternatively, you can water in your plants with Maxicrop Liquid Seaweed — a natural root stimulator.
Be careful not to overfeed, as this will promote top growth over root development.
Watering
For the first two weeks, transplanted slips need to be kept moist until they are established. After that, they need very little water and tolerate dry soil very well.
Keep in mind that the tubers are 8 to 12 inches under the soil where moisture is held much longer than on top of the soil. You may want to purchase a moisture meter to check the soil for dryness at the root depth.
Apply 1 inch of water once a week during the first few weeks. Stop watering when the plants are about 3 to 4 weeks from harvest. This will prevent the mature tubers from splitting.
Note: Too much moisture will cause the tubers to rot.
Care and Maintenance
It’s important to keep your beds weed free until the vines have grown enough to cover the soil. Doing so, especially during the first month will improve the quantity and quality of your harvest.
Mulching is unnecessary because the vines will eventually cover the exposed soil and help prevent more weeds from popping up.
Every spot where a leaf node touch the ground, the plant sends out roots that can eventually yield more sweet potatoes.
Insects and Other Pests
If you’ve planted your potatoes in in-ground beds, you may experience problems with moles or voles. (One of the advantages of raised beds or containers is that you’re less likely to be visited by them.)
The best way to rid your garden of these pests is to apply Mole Scram, a safe, organic repellent made from castor bean oil. The oil is absorbed by the insects that the tunneling terrorists eat, thereby upsetting their stomachs and driving them away.
Other small animals like rabbits, mice, rats, squirrels, and even raccoons, may try to dig up your garden. One option for repelling them is to use Fox Urine or Coyote Urine. Marshall Grain Co. sells predator urines that can be put out with a small plastic bottle containing a cotton ball. Simply wet the cotton ball with the urine. The re-usable bottle even has a hanger so that you can place it on a fence nail or even a plant stem around the area you want to protect. Each bottle protects about 100 square feet. The smell will convince any critters in the area that there is a dangerous predator nearby and encourage them to look elsewhere for food. The scent remains for about 30 days and can be reapplied as needed.
Insects that can attack sweet potatoes include: Root-knot nematodes, wireworms, flea beetles, beetles, cutworms, and weevils.
Crop rotation can greatly reduce your chances of bug infestations, but most of us don’t have enough space for that. Fortunately, there are a number of safe, organic products you can use right up to the day of harvest that are also safe for our pollinators.
One such product is all-natural, organic Azadirachtin, a key ingredient in 100% Neem Oil, which can be used as a soil drench against root-knot nematodes, or as a foliar spray for crawling and flying insects.
Another organic foliar spray is Organicide Bee Safe 3-in-1 insecticide, fungicide and miticide. Bee Safe 3-in-1 relies on natural Sesame Oil to kill many insect pests, mites and fungal problems.
Garlic Juice also works great against cutworms and weevils. Other options are Bacillus thuriengensis (Bt) or Spinosad.
Note: 70% Neem Oil Extract does not contain Azadirachtin. Use the 100% product.
Note: Never spray oil-based products on your plants while the sun is bearing down on them. The oil can react with sunlight to burn your plants. Always wait until the plant is shaded, or spray in the early morning (best time) or evening.
Diseases
Diseases that can infect sweet potatoes are leaf spots, black rot, and Fusarium stem rot.
Leaf spots are easy to treat with organic products that contain Clove, Neem, Rosemary, or Thyme oils.
Many fungal problems are brought on by over-watering, so first and foremost, make sure you are watering properly. Many fungal problems can be treated with Dusting Sulfur, Sulfur Spray, Neem Oil, or Copper Soap.
Harvesting Instructions
You can harvest the leaves and eat them as greens while the plant is maturing. Just make sure that you don’t harvest too many at a time. Always leave enough to keep the plant growing.
Harvest tubers when they reach 5 to 6 inches in length and about 2 inches in diameter as these are the best quality. One sweet potato plant should yield at least two pounds of vegetables.
You’ll know they are ready to harvest when the leaves start turning yellow. If you’re not sure, you can always do a test dig to see if they’re big enough to pull. But be sure to give your potatoes the full number of days to maturity indicated for the variety you are growing before you attempt to harvest them. Once the tops are dead, pull any remaining potatoes. Leaving them in the ground will cause the rotting and ruin your harvest.
The root has a very delicate skin that is easily bruised at harvest. Take care not to bruise them with your harvesting tools or your hands. Even dropping the potatoes into a harvest bucket can injure the skin.
Curing
Sweet potatoes must be “cured” before you can eat them. Without curing, they will not achieve their sweet flavor. During the drying process, sweet potatoes transfer their starches into sugars that give it its flavor.
Cure sweet potatoes by allowing them to dry on the ground for two to three hours, and then place in a warm room for 8 to 10 days. Curing also helps heal any cuts or bruises that may have occurred and toughens the skin for winter storage. Sometimes your soil can cause discoloring of your potatoes. This is nothing to be concerned about and doesn’t harm the storage life or the taste.
After curing, store them in a cool (50°F - 60°F), dry location. Properly cured sweet potatoes should keep the entire winter and perhaps even longer.
Tip: To get the most nutrition out of your sweet potatoes, bake them whole in the oven.
Conclusion
Like anything else, successful potato growing is as much an art as it is a science. Even experienced gardeners sometimes have crop failures, which may be due to weather or other factors outside your control. If you are disappointed with the results of your first crop, try again and don’t be afraid to modify your methods. And of course, ask us for help! The staff at Marshall Grain Co. are always ready to answer your questions and help you find solutions to your gardening problems.
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