The Sweet Potato
) is a dicotyledonous
plant that belongs to the
. Its large,
, sweet tasting tuberous roots
are an important root vegetable
(Purseglove, 1991; Woolfe,
1992). The young leaves and shoots are sometimes eaten as greens
. Of the approximately 50 genera
and more than 1,000 species of Convolvulaceae, I. batatas
is the only crop plant
of major importance – some others are used
locally, but many are actually poisonous.
The sweet potato is only distantly related to the potato
). The softer,
orange variety is commonly marketed as a "yam"
in parts of North America, a
practice intended to differentiate it from the firmer, white
variety. The sweet potato is very distinct from the actual yam,
which is native to Africa and Asia and belong to the monocot
. To prevent confusion, the United States
Department of Agriculture requires that sweet potatoes labeled as "yams" also
be labeled as "sweet potatoes".
The genus Ipomoea
that contains the
sweet potato also includes several garden flowers called morning glories
, though that term is not
usually extended to Ipomoea batatas
. Some cultivars
of Ipomoea batatas
are grown as
ornamental plants; the slightly ambiguous name "tuberous morning glory"
be used in a horticultural
This plant is a herbaceous perennial vine
alternate heart-shaped or palmately lobed leaves
and medium-sized sympetalous flowers
edible tuberous root
is long and
tapered, with a smooth skin whose colour ranges between red,
purple, brown and white. Its flesh ranges from white through
yellow, orange, and purple.
Origin, distribution and diversity
Sweet potatoes in the field.
Sweet potatoes are native to the tropical parts of South America
, and were domesticated there at
least 5000 years ago.
(1988) postulated that the centre of origin of I. batatas
was between the Yucatán Peninsula of Mexico and the
mouth of the Orinoco River in Venezuela. The 'cultigen' had
most likely been spread by local people to the Caribbean and South America by
Zhang et al.
(1998) provided strong
supporting evidence that the geographical zone postulated by Austin
is the primary centre of diversity. The much lower molecular diversity found
in Peru-Ecuador suggests
that this region be considered as secondary centre of sweet potato
The sweet potato was also grown before western exploration in
, where it is known as the
. Sweet potato has been radiocarbon-dated in
Islands to 1000 AD, and current thinking is that it was
brought to central Polynesia circa 700 AD, possibly by Polynesians
who had traveled to South America and back, and spread across
Polynesia to Hawaii and New Zealand from there.
It is possible however, that
South Americans brought it to the Pacific. The theory that the
plant could spread by floating seeds across the ocean is not
supported by evidence. Another point is that the sweet potato in
Polynesia is the cultivated Ipomoea batatas
, which is
generally spread by vine cuttings, and not by seeds.
Sweet potatoes are now cultivated throughout tropical and warm
temperate regions wherever there is sufficient water to support
According to the Food
and Agriculture Organization
(FAO) statistics, world production
in 2004 was 127,000,000 tonnes. The majority comes from China, with a
production of 105,000,000 tonnes from
About half of the Chinese crop
is used for livestock feed.
production is greatest in countries where sweet potatoes are a
staple of human consumption, led by Papua New Guinea at 550 kg per person per year, the Solomon
Islands at 160 kg, Burundi and Rwanda at
130 kg and Uganda at
20,000 tonnes of sweet potatoes are produced annually in New Zealand, where sweet potato is known by its Māori name, kūmara.
It was a
staple food for Māori before European contact.
Carolina, the leading
state in sweet potato production, provided 38.5% of the 2007 U.S.
production of sweet potatoes.
California, Louisiana, and
Mississippi compete closely with each other in production.
Louisiana has been a long-time major producer, once second only to
North Carolina, and closely followed by California, until the
latter began surpassing it in 2002. In 2007, California produced
23%, Louisiana 15.9%, and Mississippi 19% of the U.S. total.
The town of Opelousas, Louisiana's "Yambilee" has been celebrated
every October since 1946. The Frenchmen who established the first
settlement at Opelousas in 1760 discovered the native Attakapas,
Alabama, Choctaw, and Opelousas Indian tribes eating sweet
potatoes. The sweet potato became a favourite food item of the
French and Spanish settlers, and thus continued a long history of
cultivation in Louisiana.
Mississippi has about 150 farmers presently growing sweet
potatoes on about , contributing $19 million dollars to the state's
economy. Mississippi's top five sweet potato
producing counties are Calhoun, Chickasaw, Pontotoc, Yalobusha, and Panola. The National Sweet Potato Festival is held
annually the entire first week in November in Vardaman (Calhoun County), which proclaims itself as "The
Sweet Potato Capital".
Kentucky celebrates the sweet potato annually with its Tater
Day Festival on the first Monday of April. The town of Gleason,
Tennessee celebrates the sweet potato on Labor Day weekend with its Tater Town
Freshly dug sweet potato.
Sweet Potatoes at a shop in
An ornamental sweet potato of the "Ace
of Spades" cultivar
The plant does not tolerate frost
. It grows
best at an average temperature
abundant sunshine and warm nights. Annual rainfalls of
750–1000 mm are considered most suitable, with a minimum of
500 mm in the growing season. The crop is sensitive to drought
at the tuber initiation stage 50–60 days after planting and is not
tolerant to water-logging, as it may cause tuber rots and reduce
growth of storage roots if aeration is poor (Ahn, 1993).
Depending on the cultivar and conditions, tuberous roots mature in
two to nine months. With care, early-maturing cultivars can be
grown as an annual
summer crop in
areas, such as the
northern United States. Sweet potatoes rarely flower
when the daylight is longer than 11 hours, as
is normal outside of the tropics
. They are
mostly propagated by stem or root cuttings or by adventitious roots
called "slips" that grow out from the tuberous roots during
storage. True seeds are used for breeding only.
Under optimal conditions of 85 to 90% relative humidity
at , sweet potatoes can
keep for six months. Colder temperatures injure the roots.
They grow well in many farming conditions and have few natural
enemies; pesticides are rarely needed. Sweet potatoes are grown on
a variety of soils, but well-drained light and medium textured
soils with a pH range of 4.5-7.0 are more favourable for the plant
(Woolfe, 1992; Ahn, 1993). They can be grown in poor soils with
little fertilizer. However, sweet potatoes are very sensitive to
aluminium toxicity and will die about 6 weeks after planting if
lime is not applied at planting in this type of soil (Woolfe,
1992). Because they are sown by vine cuttings rather than seeds,
sweet potatoes are relatively easy to plant. Because the rapidly
growing vines shade out weeds, little weeding is needed, and
farmers can devote time to other crops. In the tropics, the crop
can be maintained in the ground and harvested as needed for market
or home consumption. In temperate regions, sweet potatoes are most
often grown on larger farms and are harvested before first
China is the
largest grower of sweet potatoes, providing about 80% of the
world's supply; 130 million tons were produced in one year (in
1990; about half that of common potatoes).
most of China's sweet potatoes were grown for human consumption,
but now most (60%) are grown to feed pigs
rest are grown for human food and for other products. Some are grown for
export, mainly to Japan.
China grows over 100 varieties of sweet potato.
potatoes very early became popular in the islands of the Pacific Ocean, spreading from
Polynesia to Japan and the
One reason is that they were a reliable
crop in cases of crop failure of other staple foods due to typhoon
flooding. They are featured in many favorite dishes
in Japan, Taiwan, the
Philippines, and other
island nations. Indonesia, Vietnam, India, and some
other Asian countries are also large sweet potato growers.
Uganda (the third largest grower after Indonesia),
Rwanda, and some
other African countries also grow a large crop which is an
important part of their peoples' diets. North and South America
, the original home of the
sweet potato, together grow less than three percent of the world's
supply. Europe has only a very small sweet potato
production, mostly in Portugal.
In the Caribbean, a variety of the sweet
potato called the boniato
is very popular. The flesh of
the boniato is cream-coloured, unlike the more popular orange hue
seen in other varieties. Boniatos
are not as sweet and
moist as other sweet potatoes, but many people prefer their
fluffier consistency and more delicate flavor. Boniatos
have been grown throughout the subtropical world for centuries, but
became an important commercial crop in Florida in recent
Sweet potatoes were an important part of the diet in the United
States for most of its history, especially in the Southeast. From
the middle of the 20th century, however, they have become less
popular. The average per capita consumption of sweet potatoes in
the United States is only about per year, down from in 1920.
Southerner Kent Wrench writes: "The Sweet Potato became associated
with hard times in the minds of our ancestors and when they became
affluent enough to change their menu, the potato was served less
New Zealanders grow enough kūmara to provide each person with per
year, and also import substantially more than this from
Nutrition and health benefits
Besides simple starches, sweet potatoes are rich in complex carbohydrates
, dietary fiber
(a vitamin A
nutrient), vitamin C
, and vitamin B6
. Pink and yellow varieties
are high in carotene, the precursor of vitamin A.
In 1992, the Center for Science in
the Public Interest
compared the nutritional value of sweet
potatoes to other vegetables. Considering fibre content, complex
A and C,
, and calcium
sweet potato ranked highest in nutritional value. According to
these criteria, sweet potatoes earned 184 points, 100 points over
the next on the list, the common potato.(NCSPC)
Sweet potato varieties with dark orange flesh have more beta carotene
than those with light coloured
flesh, and their increased cultivation is being encouraged in
Africa, where vitamin A deficiency is a serious health problem.
Despite the name "sweet", it may be a beneficial food for diabetics
, as preliminary studies on animals have
revealed that it helps to stabilize blood sugar levels and to lower
insulin resistance. Some Americans, including television
personality Oprah Winfrey
advocating increased consumption of sweet potatoes both for their
health benefits and because of their importance in traditional
A 100g root is reported to contain 108-121 calories, 68.5-72.3 g
water, 1-1.7 g protein, 0.2-0.4 g fat, 25-31.0 total carbohydrate,
0.7-1.0 g ash, 21–36 mg Ca, 38–56 mg P, 0.7-2.0 mg
Fe, 10–36 mg Na, 210–304 mg K, 35-5,280 µg
beta-carotene equivalent, 0.09-0.14 mg thiamine,
0.04-0.06 mg riboflavin, 0.6-0.7 mg niacin, and
21–37 mg ascorbic acid.
The peptic substance (0.78 percent total, 0.43 percent soluble)
present in fresh tubers contains uronic acid (60 percent) and
methoxyl (4 to 5 percent). Other constituents include phytin (1.05
percent), two monoaminophosphatides (probably lecithin and
cephalin), organic acids (oxalic acid), phytosterolin, phytosterol,
resins, tannins, and colouring matter. Sweet potato contanins
calcium, 30; magnesium, 24; potassium, 373; sodium, 13; phosphorus,
49; chlorine, 85; sulphur, 26; iron, 0.8 mg/100g; iodine,
4.5 µg/kg; manganese, copper and zinc are present in traces
(Hug et al., 1983).
A sweet potato.
The roots are most frequently boiled, fried, or baked. They can
also be processed to make starch
Although the leaves and shoots are also edible, the starchy
tuberous roots are by far the most important
product. In some tropical
areas, they are a
"Amukeke" (sun dried slices of storage roots) and "inginyo" (sun
dried crushed storage roots) are a staple food for people in
northeastern Uganda (Abidin, 2004). Amukeke is mainly for
breakfast, eaten with peanut
generally eat this food while they are drinking a cup of tea in the
morning, around 10 am. Inginyo will be mixed with cassava flour and
, to make food called "atapa".
People eat "atapa" with smoked fish cooked in peanut sauce or with
leaves cooked in peanut
Candied sweet potatoes
are a side dish consisting
mainly of sweet potatoes prepared with brown sugar, marshmallows
, orange juice
, marron glacé
, or other sweet ingredients.
Often served in America on Thanksgiving
, this dish represents traditional
that prepared with the indigenous peoples of the
settlers first arrived.
Sweet potato pie
is also a traditional favourite dish in southern U.S.
Sweet potatoes slices
are fried in bacon drippings
and eaten with the bacon on toast. This is a traditional autumn
breakfast food in rural Kentucky.
Baked sweet potatoes
are sometimes offered in
restaurants as an alternative to baked
. They are often topped with brown sugar and butter.
Republic, sweet potato is enjoyed for breakfast.
China, sweet potatoes are often baked in a large iron drum and sold
as street food
Sweet potato fries
or chips are another common
preparation, and are made by julienning
and deep frying
sweet potatoes, in the
fashion of French fried
Sweet potato greens
are a common side dish in
, often boiled or
sautéed and served with a garlic and soy sauce mixture, or simply
salted before serving. They, as well as dishes featuring the sweet
potato root, are commonly found at bento
: piān-tong) restaurants, .
The young leaves and vine tips of sweet potato leaves are widely
consumed as a vegetable in West African countries (Guinea, Sierra
Leone and Liberia, for example), as well as in northeastern Uganda,
East Africa (Abidin, 2004). According to FAO leaflet No. 13 - 1990,
sweet potato leaves and shoots are a good source of vitamins A, C,
and B2 (Riboflavin), and according to research done by A.
Khachatryan, are an excellent source of lutein
are boiled in water or
cooked by microwave
Sweet potato butter
can be cooked into a gourmet
In northeastern Chinese
, sweet potatoes are often cut into chunks and fried,
before being drenched into a pan of boiling syrup.
In Korean cuisine
, sweet potato
starch is used to produce dangmyeon
). Sweet potatoes are
also boiled, steamed, or roasted, and young stems are eaten as
: Boiled sweet
potato is the most common way to eat it at home. Also, the use in
(roasted sweeted potato) is a delicacy in winter,
sold by hawkers. Daigaku-imo
is a baked sweet potato
. In imo-gohan
, slices or small blocks of sweet potato are
cooked in rice
. It is also served in
, boiled and typically flavoured with
. Because it is sweet and starchy, it is
used in imo-kinton
such as ofukuimo
. Shōchū, a Japanese spirit normally made from the fermentation of
rice, can also be made from sweet potato, in
which case it is called imo-jōchū.
In New Zealand, Māori traditionally cooked their kūmara in
Rocks were placed on a fire in a large hole. When the fire died
out, kūmara and other food was wrapped in leaves and placed on the
hot rocks, then covered with earth. The kūmara was dug up again
several hours later. The resulting food was very soft and tender,
as though steamed. However, hangi are rare in modern New Zealand,
and New Zealanders, Maori or Pakeha are more likely to consume it
baked, boiled, or deep-fried (such as in kumara chips) than they
are in hāngi.
In Malaysia, sweet potato is often cut into small cubes and cooked
with yam and coconut milk (santan) to make a sweet dessert called
. A favourite way of cooking sweet potato is
deep frying slices of sweet potato in batter, and served as a
tea-time snack. In houses, sweet potatoes are usually boiled. The
leaves of sweet potatoes are usually stir-fried with only garlic or
with sambal belacan
and dried shrimp by the Malaysian
In South America
, the juice of red
sweet potatoes is combined with lime
juice to make a dye
. By varying the proportions of the juices, every
shade from pink to purple to black can be obtained. (Verrill
All parts of the plant are used for animal fodder
Sweet potatoes or camotes are often found in Moche
Several selections are cultivated in gardens as ornamental plants
for their attractive foliage, including the dark-leafed cultivars
'Blackie' and 'Ace of Spades' and the chartreuse-foliaged
'Margarita'. The species called wild sweet potato vine, man root,
or man-of-the-earth is not edible, but it is cultivated as an
Taiwanese companies are making alcohol
from sweet potato.
Although it is sometimes called a yam, the sweet potato is not in
family, nor is it closely
related to the common potato
. The first
Europeans to taste sweet potatoes were members of Columbus
' expedition in 1492. Later
explorers found many varieties under an assortment of local names,
but the name which stayed was the indigenous Taino
name of batata
. This name
was later transmuted to the similar name for a different
vegetable—the ordinary potato, causing confusion from which it
never recovered. The first record of the name "sweet potato" is
found in the Oxford English Dictionary of 1775.
Kumara for sale, Thames, New
Spain and Latin America
The Spanish took the Taino name batata
directly, and also
combined it with the Quechua
, to create the word patata
common potato. In Mexico and Central America, the sweet potato is called
by the Nahuatl-derived name
camote. In Peru, the Quechua
name for a type of sweet potato is kumar, strikingly
similar to the Polynesian name kumara (see
In South America, Peruvian sweet potato remnants dating as far back
as 8,000 BC have been found.
Polynesia and Australasia
(with its respective developments) is the
name for the sweet potato.
names used in local varieties
of English include kumara
(from the Māori
word kūmara), as it was the staple
food of the native Māori diet, in Australasia (in NSW it is
sometimes spelled as "Kumera", although "sweet potato" is more
common in Australia, at least in Victoria). The term is also used
in indigenous languages of Melanesia, as well as "peteita".
Guinean language of Tok Pisin, is
it known as kaukau.
Hawai i substratum names are used for the yellow Japanese
variety (紫芋, murasaki imo, lit.
"purple potato" or
, "Satsuma potato") and the purple
Okinawan variety (紅芋, beni imo
, lit. "crimson potato",
cv. Ayamurasaki), both of which are
commonly available in the marketplace. The local Japanese
names are widely recognized, with
potato” used by recent Japanese immigrant families and
”) by other groups. (Technically, yamaimo
proper name in Japanese of the native yam; however, as in English,
it is often used to refer to the sweet potato.)
It has different names in China according different regions. it is
called "Faansyu" 番薯 in Cantonese, “hongshao”(红苕) in Sichuan
province, and "hongshu"(红薯) or "ganshu"(甘薯)in other places, for
The Indonesian word for sweet potato is "ubi jalar"
. This given name is probably from the
growing characteristics of its vines. They are creeping (its
Indonesian word is "menjalar") on the ground or above soil surface.
Furthermore, the storage roots ("ubi"), which are produced by the
vines in the soil, could also be found elsewhere, far from the base
of the plant.
In the Tamil language, the sweet potato is called "sakkarai
vallikkizhangu" denoting its sweetness. It is commonly prepared
with jaggery as a candied product as well as used similar to the
potato.In Telugu, this is known as "Chilakata Dumpä", and it has
more dietary fiber. The Telugu people eat this with added sambaar,
boil in water, and make it Tandoor in a clay oven.The Malayalam
word for sweet potato is 'madhura kizhangu'. "Batata" or "bataka"
is the commonly used word for all varieties of potato in Marathi
, the two languages of western
states of India, suggesting an origin by way of the Portuguese.
"Ratala" is, however, the name only reserved for sweet potatoes in
. In Hindi, it is called
shakarkand("शकरकंद")or "rut-aaloo". In Oriya, it is called
kandhamula. In Assamese
, it is
called "meetha aloo" or "ronga aloo".
It is called "bathala" in Sinhala
The orange-fleshed variety common in the mainland U.S. and sold
alongside the Japanese and Okinawan cultivars is locally called
"sweet potato" or "yam." The purple Okinawan sweet potato is
sometimes confused with the purple yam called ube
. The general Japanese term for sweet potato is
, literally "potato from Satsuma Province"
. (It is
which is used in imoshōchū
, the tubers are
called khoai lang
, and the leaves are called rau
term for sweet potato
". The planting season in the
Philippines lasts from
February to May.
It is one of the major root crops of the
country, and is considered a major food source in many provinces.
The leaves, called "talbós ng kamóte
", are boiled in water
for about five minutes and is then eaten as a vegetable dish. A
decoction of the leaves is administered to dengue
patients in the hopes of increase in blood platelet
levels, but no scientific
studies have been done to prove its efficacy as a herbal
The Korean name for sweet potato is "goguma" (Hangul
addition to the Fulani and Twi names, which probably are the source
of the United States usage "yam", in Kenya "ngwaci" is
the Kikuyu word for sweet potatoes, 'ikwachi
bia mukou' by the Ameru.
word is "viazi tamu", literally sweet potatoes. In Uganda, people
call it simply potato. Meanwhile, the 'solanum' potato is called
'Irish' potato. In SiNdebele (Ndebele), spoken in Zimbabwe and
South Africa, it is called "mbambayila".In Nigeria it is called
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" Leaflet No. 13 - 1990 - Sweet Potato