How Do Sweet Potatoes Grow?

 

USDA Hardiness Zones 9 - 11

 

The sweet potato is a herbaceous perennial vine that produces sweet-tasting tubers.  The plant has heart-shaped leaves and medium-sized, trumpet-shaped flowers with fused petals. The tuberous roots are long and rounded or tapered, and range in color with orange, brown, beige, red, purple, yellow and pink varieties. 

 

The sweet potato is a warm-season crop that originated in the tropics. It is not frost tolerant. It is pest and disease-resistant and grows in well-drained soil. However, it is sensitive to getting waterlogged and tuber rot if the soil aeration is poor, so loamy soil is the best growing medium.

 

Maturation time varies vastly between varieties, with roots generally maturing in a span of three to nine months. As a general rule, this tropical crop requires several months of warm weather to fully ripen. Some early-maturing cultivars are grown as an annual summer crop in northern, temperate regions.  A good way to tell when sweet potatoes are ready to harvest is when the vines begin to turn yellow - or, in the northern United States, just before the first frost. 

 

Seasonal Growth

 

Health Benefits

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Orange-fleshed sweet potatoes are one of the top sources of beta-carotene, which the body converts into vitamin A. 

 

With 214% of the recommended daily value of vitamin A per serving, sweet potatoes have an incredible ability to raise blood levels of vitamin A. In studies in Africa, 3.5 ounce servings of sweet potatoes were found particularly successful in meeting from 35% up to 90% of vitamin A dietary needs, particularly in children.

 

Adding a small serving of 3 to 5 milligrams of fat to sweet potato meals greatly increases beta-carotene benefits. The World’s Healthiest Foods organization suggests that just one tablespoon of extra virgin olive oil per four servings of sweet potato provides 3.5 grams of fat. 

 

The pigments in purple-fleshed sweet potatoes contain anthocyanins - penodins and cyanins - with antioxidant and anti-inflammatory properties. Studies show that when passing through the digestive tract, these anthocyanins and other phytonutrients in sweet potatoes help to lower the risk of damage from heavy metal residues (including mercury and arsenic) and other oxygen radicals. 

 

Storage proteins called sporamins are produced by the sweet potato plant to help it heal when it is damaged. These proteins also play a significant role in sweet potatoes’ antioxidant abilities.

 

Color-producing phytonutrients such as pigmenting anthocyanins have been shown to reduce inflammation in brain and nerve tissue in animal studies.

 

Animal studies have also shown that sweet potatoes effectively reduce the body’s fibrinogen levels. Fibrinogen is essential for the body’s blood clotting and wound-healing abilities, but, in excess, it can trigger inflammation in nerve tissue and break down the myelin that protects nerve cells, leading to health problems like multiple sclerosis. Sweet potato consumption reduces inflammation while reducing fibrinogen levels.

 

Most people trying to control their blood sugar shy away from starchy vegetables, but the sweet potato is an exception. The sweet potato’s good levels of dietary fiber (6.6 grams) combined with the root vegetable’s ability to increase adiponectin (a protein hormone produced by fat cells that help regulate insulin metabolism) help to control blood sugar. People with poorly-regulated insulin, such a type 2 diabetics, tend to have lower levels of adiponectin, which sweet potatoes can help to increase.

 

History

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The sweet potato traces its tuberous roots back to Central and South America, where it it was grown at least 5,000 years ago by Native American people. 

 

In Peru, archaeologists have found remnants of sweet potatoes and evidence of their cultivation dating back to 8,000 BCE. The Incas called it batata, from which the plant derives its scientific name. Batata is also thought to be the origin of the word “potato,” although it is not present in the potato’s latin name, solanum tuberosum. From Central and eastern South America, it is believed the sweet potato spread to the Caribbean by 2500 BCE. 

 

Evidence of sweet potato cultivation in Polynesia dating back to 1000 CE suggests sweet potatoes arrived in the south Pacific prior to western exploration. The theory is that Polynesian explorers who traveled to South America returned home with the sweet potato, then carried it to Hawaii and New Zealand around 700 CE.

 

Spanish explorers Christopher Columbus, Francisco Pizarro and Vasco Núñez de Balboa are thought to be responsible for the sweet potato’s introduction to the western world during the Age of Exploration in the late 15th and early 16th century, when the explorers discovered the root vegetable in the West Indies, Peru and Central America, respectively. They returned to Spain with the sweet potato and from there it spread throughout Europe and into Asia.

 

In European countries such as England, the sweet potato was immediately accepted as a delicacy - unlike the white Irish potato, which took years to gain acceptance. In colonial days in the United States, George Washington grew sweet potatoes on his farm in Virginia. Centuries later, at the turn of the 20th century, George Washington Carver would discover more than 100 uses for the sweet potato, including as an alternative to corn syrup.

 

Propagation

 

Unlike most plants, the sweet potato is not propagated by seed, but instead, by “slips” which are sprouts that grow from existing sweet potatoes.  Slips are available at nurseries, garden stores or from local farmers.

 

Commercial growers use a mechanical planter with which they can plant 8 rows at a time. 

 

Harvest

 

Depending on the variety, the edible, tuberous sweet potatoes mature anywhere from 100 to 120 days. They are ready to harvest when the vines begin to turn yellow or, in the north, just before the first frost. Cool soil temperatures reduce the quality of sweet potatoes and limit their shelf life.

 

Commercial growers use special harvesters to dig out the potatoes.

 

Sweet potatoes need to sit and “cure” before they are eaten, otherwise they don’t taste sweet - or bake well. 

 

To cure sweet potatoes, they are first cleaned of debris and thoroughly washed.  Then they are dried and stored in a dark, well-ventilated and warm  (80 to 90 degrees Fahrenheit) room for 5 to 10 days. Curing sweet potatoes allows them to form a second skin over any bruises or scratches they suffered in the harvesting process. They also need the time to develop their sweetness by converting their starches into sugars.  A freshly dug sweet potato is not as sweet as a cured one. 

 

Storage

 

Cured sweet potatoes keep for up to six months at an average temperature of 55 to 60 degrees Fahrenheit in a high humidity environment, like a basement or a pantry.

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Fun Facts

 

China is the world’s leading producer of sweet potatoes, accounting for approximately 80% of the international market. China is followed in production by Uganda, Nigeria, Indonesia and Vietnam (FAOSTAT, 2010).

 

Sweet potato shoots and leaves are actually edible, but it’s the plants tuberous roots that are its most important product. In some tropical regions of the world, such as the Philippines, sweet potatoes are a staple food crop. African countries such as Uganda, Liberia, Sierra Leone and Kenya also grow sweet potatoes as a staple food source.

 

Around the world, sweet potatoes are commonly baked, boiled, or steamed. They are an ingredient in pies, soups, casseroles, curry dishes, juices and desserts. 

 

Sweet potato pie and sweet potato pancakes are traditional dishes in Southern U.S. cuisine. The sweet potato also plays a starring role in traditional Thanksgiving feasts in the United States, where it is served candied, baked or in casseroles.

 

There are about 6,500 varieties of sweet potatoes worldwide, with skin colors that range from brown, beige or yellow to pink or dark red, and flesh colors that vary from beige to white, orange, yellow, red, or even shades of purple. Here are some popular varieties:

 

Most sweet potatoes produced in the United States are Beauregard or Jewell. 

Other sweet potato varieties include Centennial (copper skin, pale orange flesh), Garnet (red skin, orange flesh), White Delight (purplish-pink skin, white flesh), Carolina Ruby (dark red skin, dark orange flesh), Speckled Purple (purple skin, speckled magenta flesh), and Korean Purple (speckled purple-beige skin and white flesh).

 

 

Grow it Yourself:

 

Sweet potatoes are a very easy crop to grow. If the soil is warm and moist, a sweet potato simply dropped on the ground will likely take root and grow. 

 

There are two ways to grow your own sweet potatoes:

 

1.  Plant entire sweet potatoes.  

- Choose organic medium-sized, uncracked sweet potatoes. 

- Store them in a well-lit room, between 65 and 70 degrees Fahrenheit, for 90 days before the last spring frost date

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- Using a 1.5 gallon pot for every two potatoes, embed them at a 45 degree angle for 90 more days, keeping the soil warm and moist.

 

- Plant the potatoes at an angle allowing the sprouts (slips) to grow above ground.

 

- Once the slips reach 6-12 inches in height, they are ready to be transplanted outdoors.

 

- Follow instructions below on how to plant slips.

 

2. Buy the slips from a local garden store, nursery or farm.

 

- Sweet potatoes like loamy, well-draining soil with a pH of between 5.8 and 6.2 and rich, organic compost. Thoroughly dampen the bed before planting. Sweet potatoes are an ideal crop for areas with sandy soil.

 

- Plant slips after the last danger of frost has passed.  Put them in about 12 to18 inches apart, leaving 3 feet between rows to give the vines ample room to spread. 

 

- After they’re in the ground, cover them with plastic or black fabric mulch to warm the soil and to protect the slips from sun damage.

 

- Water weekly. Vines spread quickly and need to be weeded well but carefully so as not to damage the roots or growing tubers.

 

- Give the plants a boost by adding a time-release fertilizer that contains potassium.

 

- Check for ripeness after 100 days.  Dig the sweet potatoes out gently, remember they need to be cured, and enjoy!