Sweet Potato

The sweet potato or sweetpotato is a dicotyledonous plant that belongs to the bindweed or morning glory family, Convolvulaceae. Sweet potato is native to the tropical regions of the Americas. The botanical name of sweet potato is Ipomoea batatas.The sweet potato plant is a branching, creeeping vine with spirally arranged lobed, heart shaped leaves and white or lavender flowers.



It's large, starchy, sweet-tasting tuberous roots are used as a root vegetable. The young shoots and leaves are sometimes eaten as greens. The sweet potato is widely cultivated in tropical and warm temperate climates and is an important food crop in the southern United States, tropical America and the Caribbean, the warmer islands of the Pacific, Japan, and parts of Russia.


Table of Contents


Height(Avg)

6 - 8 inches


Width-Circumference (Avg)

about 12 inches


Approximate pH

5.3 - 5.6


Varieties of Sweet Potato


The fastest-growing sweet potato varieties have orange flesh, but you might also consider varieties with white, yellow, or even purple flesh. Note that orange-flesh varieties cook up moist; white and yellow sweet potatoes become creamy; purple sweets are dry and starchy.

  • ‘Beauregard’ (90 days) originally comes from Louisiana, but grows well in the north, too. It has dark red roots, dark orange flesh, and stores well.

  • 'Centennial’ (100 days) is the leading variety in the U.S. It is carrot-colored and has a good storage life. It is also a good producer for the North.

  • ‘Georgia Jet’ (90 days); Red skin covers moist, deep orange flesh. Extremely fast-growing type; good for the North.

  • ‘Jewel’ (100 days) has copper-colored skin and orange flesh; disease-resistant; stores well.

  • ‘Stokes’ offers a vibrant purple color and is full of extra health benefits; cooks well in savory dishes and mashes.

  • ‘Vardaman’ (110 days) is a bush type and good for small gardens; it has unique blue/purple foliage, golden skin, and reddish-orange flesh; stores well.

  • ‘White Yam’ (100 days); also called ‘White Triumph’. White skin covers dry white flesh. One of the oldest sweet potato varieties. Has compact vines.


Planting Sweet Potato


Choose a sunny spot with well-drained soil. Sweet potatoes aren’t too picky, but they do prefer soil on the sandier side. They need plenty of air space in the soil for roots to reach down. If your soil is clay, rocky, or compacted, consider raised beds.

Add compost as well as perlite and/or coconut coir to the growing area to build up fertile, loamy soil down to 8 to 10 inches. Avoid adding animal manure, including pelleted chicken manure. It can result in spindly and/or stained roots. Also, avoid heavy nitrogen fertilizers which produce lush leaf growth at the expense of the sweet potato!


When to Plant Sweet Potatoes

  • You won’t plant your slips until 3 to 4 weeks after the last spring frost, once nighttime temperatures have reached at least 55°F (13°C). The trick is to plant them early enough for them to mature properly, but not so early they get killed by a late spring frost.

  • If you ordered slips, unpack them right away. Stick the roots in water for a day or so, and they’ll perk up.

How to Plant Sweet Potatoes

  • Create raised mounds 6 to 8 inches tall and about 12 inches wide.

  • Plan 3 feet between mounds so that there is enough space for vines to run.

  • Plant the slips on a warm, overcast day, when the soil temperature has reached 60°F.

  • Break off the lower leaves, leaving only the top ones.

  • Set the slips deep enough to cover the roots and the stem up to the leaves. Sweet potatoes will form on the nodes, 12 to 18 inches apart.

  • Water with a high-phosphorus liquid fertilizer, then water generously for 7 to 10 days to make sure that the plants root well.


Sweet Potato Care


Light


Be sure to plant your sweet potatoes in full sun to part shade. They generally prefer full sun but appreciate some afternoon shade in hot, dry regions.


Soil


Sweet potatoes prefer soil that is well-drained but high in organic matter. Sandier soil is preferable to dense, clay soil.


Water


Once established, sweet potatoes will tolerate growing in dry soil. It's best to keep it evenly moist with 1 inch of water given once a week. Don't water your sweet potatoes during the final three to four weeks prior to harvest to prevent the mature tubers from splitting. Keep the plants moist, especially during dry spells.


Prune


Do not prune sweet potato vines; they should be vigorous.


Temperature and Humidity


Sweet potatoes should not be planted outdoors until the temperature of the soil has warmed to 60 degrees Fahrenheit. They need soil growing temperatures between 60 to 85 degrees Fahrenheit and an air growing temperature of 65 to 95 degrees Fahrenheit. Choose short-season varieties if you live in the northern part of the country.


Fertilizer


Sweet potatoes are not heavy feeders, but it's important to give them balanced nutrition, typically with proper soil preparation. Overfeeding tends to promote growth of foliage rather than tubers. The best approach is to add compost to the beds before planting the sweet potatoes. Alternatively, you can apply an organic liquid fertilizer to the soil prior to planting.


Harvesting

  • You can start digging up the potatoes as soon as they are big enough for a meal.

  • Harvest when the leaves and ends of the vines have started turning yellow or about 100 days from planting.

  • Loosen the soil around each plant (18 inches around, 4 to 6 inches deep) to avoid injuring the root. Cut away some of the vines.

  • Pull up the plant’s primary crown and dig up the roots by hand. Handle the sweet potatoes carefully, as they bruise easily.

  • Shake off any excess dirt; do not wash the roots.

  • Complete harvesting by the first fall frost.

How to Cure and Store Sweet Potatoes

  • Curing sweet potatoes gives them that sweet taste and also allows a second skin to form over scratches and bruises.

  • To cure, store 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. Arrange sweet potatoes so that they are not touching.

  • After curing, discard bruised sweet potatoes, then wrap each one in newspaper.

  • Carefully pack in a wooden box or basket. Store in a root cellar, basement, or the like with a high humidity at 55°F to 60°F. The roots should last for about 6 months.

  • Handle sweet potatoes carefully; they bruise easily.


Pests and Plant Diseases


Pests


1. Sweet Potato stem borer


Symptoms: Larvae bores into the stem leading to the storage roots. Feeding in the crown region leads to wilting, yellowing and dying of plant. The borers can be easily identified by the presence of fecal matter on the soil surface and holes on the stem.


Comments: Larva is light-purple and/or yellowish-white in color.


Management: Keep the field free from weeds especially Ipomoea spp. Fallow the land for few season if infestation is more. Use insect free planting material. Use pheromone traps to monitor and control the insect.


2. White grub


Symptoms: Grub feeds on underground parts including main stem and roots. They also feed on tubers by making tunnels. The infected plant become wilted and die eventually.


Comments: White grub are the larvae of scarab beetles commonly called as May and June beetles. The grubs are white in color and appear C shape. They generally feed on soil, organic matter and plant materials.


Management: Cultural practice: Deep summer ploughing to expose grub and pupa present in soil. Provide proper drainage to soil to avoid excess moisture. Follow crop rotation with soybean to reduce grub population. Application of biocontrol agents like Bacillus popilliae and B. lentimorbus bacteria kill the grubs.


Diseases


1. Alternaria leaf spot & Leaf and stem blight


Symptoms: Brown lesions on leaves with concentric rings resembling a target; lesions are usually restricted to the older leaves and may be surrounded by a yellow halo; small gray-black oval lesions with lighter centers may occur on stems and leaf petioles and occasionally on leaves; stem and petiole lesions enlarge and often coalesce resulting in girdling of the stem; defoliation may occur.


Comments: Stem and leaf petiole blight is much more destructive than leaf spots caused by Alternaria; stem and petiole blight is a severe disease of sweet potato in East Africa and has also been reported from Asia, South America and Cuba.


Management: Destroy all sweet potato crop residue immediately following harvest; plant resistant or tolerant sweeet potato varieties where available; plant only disease-free seed material.


2. Black rot


Symptoms: Stunted plants; wilting plants; yellowing plants; dropping leaves; plant death; circular brown-black patches of rot on tubers.


Comments: Rot continues to develop in stored tubers.


Management: Only disease-free seed material should be planted; sweet potato should not be planted in sites where sweet potato has been grown during the previous 3-4 years; transplant material should be collected from plant by making cuts above-ground; seed material should be treated with an appropriate fungicide prior to planting.


3. Fusarium root and stem rot


Symptoms: Swollen and distorted base of stems; deep, dark rot extending deep into tuber and forming elliptical cavities; growth of white mold.


Comments: Disease can be spread by infected transplants.


Management: Disease is generally not a problem if good sanitation is implemented; select only disease-free roots for seed; use cut transplants rather than slips; practice crop rotation; treat seed roots with an appropriate fungicide prior to planting.


4. Bacterial soft rot

Symptoms: Brown to black water-soaked lesions on stems and petioles which expand rapidly and and cause large areas of soft rot on the stem; stem may collapse causing several vines to wilt; entire plant may die; storage roots may develop areas of soft rot which is initially colorless, but eventually turns brown with a black margin.

. Comments: Symptoms develop after hot weather; can effect stored tubers.

Management: Avoid wounding storage roots at all stages of growth; plant only disease-free seed material; discard any stored roots which become infected with the disease; vines for transplanting should be cut above the soil surface; plant sweet potato varieties which are resistant to the disease.

5. Bacterial wilt

Symptoms: New sprouts wilting and have water-soaked bases which turn yellow-brown to dark brown in color; vascular system of the sprouts is discolored brown; infection of healthy transplants causes the lower portions of the stems to become water-soaked and turn a similar color to infected sprouts; yellow-brown streaks may develop inside storage roots and, if infection is severe, gray-brown water-soaked lesions may be present on the root surface.

Comments: The bacteria causing the disease is an important pathogen of other crops but in sweet potato it is only severe in certain regions of China where it can cause 70-80% reductions in yield.

Management: Quarantine procedures have been put in place in regions of China where the disease is severe; only disease-free storage roots should be used for planting and planting should only be done in sites free of the disease; rotating sweet potato with a flood crop such as paddy rice or a non-host such as corn or wheat can be beneficial; growing sweet potato during cooler periods of the year allows some avoidance of the disease.

6. Leaf and stem scab

Symptoms: Small brown lesions on leaf veins which become corky in texture and cause veins to shrink which in turn causes leaves to curl; lesions on stem are slightly raised and have purple to brown centers with light brown margins; scabby lesions form on stems when lesions coalesce. Comments: Leaf and stem scab is one of the most severe diseases of sweet potato; disease is most severe in regions where there is frequent fog, rain or dew accumulation and is common in Asia and Australia.

Management: Avoid the use of overhead irrigation; rotate sweet potato with other crops; use only disease-free planting material; destroy sweet potato crop residue immediately after harvest; application of appropriate fungicides can help to control the disease, good control of the disease can be achieved with benomyl and chlorothalonil where licensed for use.

7. Pox

Symptoms: Poor growth of plants; reduced yield; circular dark brown, corky lesions on tubers which are V-shaped in cross section; cracked and distorted tubers which resemble dumbells; rotting feeder roots. Comments: Disease emergence favors light, sandy soils.

Management: The most effective method of controlling the disease is through the use of resistant varieties of sweet potato; if resistant varieties are not being used then the soil should be maintained at a low pHwhich is unfavorable to the pathogen; sweet potato should be rotated with other crops which are non-hosts to prevent build up of the pathogen in the soil; fumiigation of the soil prior to planting can be an effective method of reducing the severity of the disease.

8. Sweet potato virus disease (SPVD) Sweet potato feathery mottle virus (SPFMV) and Sweet potato chlorotic stunt virus (SPCSV)

Symptoms: Sweet potato virus disease is a disease complex caused by two viruses; sweet potato chlorotic stunt virus (SPCSV) and sweet potato feathery mottle virus (SPFMV). The symptoms are sever stunting of infected plants, stunting, distorted and chlorotic mottle or vein clearing of the leaves. It is confirmed that SPCSV enhances the accumulation of SPFMV. The symptoms caused by SPCSV alone is negligible. Where as symptoms caused by SPFMV is localized, mild and often asymptomatic and won't cause significant damage to the plant. Common symptom include appearance of feathery, purple patterns on the leaves. Comments: It is estimated that SPVD causes yield loss up to 80 - 90%. The disease was first reported in 1939 from eastern Belgian Congo (present Democratic Republic of Congo). SPCSV is crinivirus of Closterviridae and SPFMV is potyvirus belong to Potyviridae. SPFMV is transmitted by a wide range of aphid species. SPCSV is transmitted by white flies (Bemisia tabaci).

Management: Use healthy cuttings for planting. Remove the infected plants and burn them. Follow crop rotation. Spray suitable insecticides to control aphids and white flies.


Benefits of Sweet Potatoes


Sweet potatoes earned the name "superfood" because of the amount of nutrients they have.


Cancer: Carotenoids in sweet potatoes might lower your risk for cancer. Purple sweet potatoes are high in another natural compound called anthocyanin that might lower your chances of getting colorectal cancer.


Diabetes: Compounds in sweet potatoes could help control blood sugar. When boiled, sweet potatoes are low on the glycemic index (GI), which means they won't raise your blood sugar as quickly as high-GI foods.


Heart disease: Research shows that sweet potatoes can lower your LDL "bad" cholesterol, which may lower your odds of heart problems.


Macular degeneration: Large amounts of beta-carotene and vitamin A, which are in sweet potatoes, can lower your chances of getting this eye disease, which is the most common cause of vision loss.


Obesity: Purple sweet potatoes may help lower inflammation in your body and keep fat cells from growing, which may help you lose weight.


Support immune function: Being rich in beta-carotene, sweet potatoes may also help support immune function. This is because vitamin A is important for maintaining the integrity of the mucous membranes in the respiratory system and gut.


Uses

  • Sweet potato leaves are used to treat irritations of the mouth and throat.

  • Sweet potato leaves can be crushed and used in ointments to help treat skin conditions such as rashes.

  • The leaves can be eaten fresh or after cooking.

  • They were used in folk remedies to treat asthma, night blindness, and diarrhea.

  • Sweet potato tubers are eaten cooked as a vegetable or may be processed into flour or starch.

  • A part of the tuber harvest is used in India as cattle fodder.

  • Sweet potatoes are widely eaten boiled as a favored snack.

  • Young sweet potato leaves are also used as baby food particularly in Southeast Asia and East Asia.

  • Purple sweet potato color is also used as a ‘natural’ food coloring.




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