Sweet potato

The sweet potato or sweetpotato (Ipomoea batatas) is a dicotyledonous plant in the morning glory family, Convolvulaceae. People grow it for its big, starchy, sweet-tasting tuberous roots, which they eat as a root vegetable. These roots are a staple food in many parts of the world. There are many kinds of sweet potatoes, and some have different colors of flesh and skin. Sometimes, people also eat the young shoots and leaves as greens. Even though sweet potatoes and regular potatoes are both tasty foods, they are only distantly related.

Sweet potatoes grew naturally in the tropical parts of South America, especially in modern-day Ecuador. Out of the about 50 genera and over 1,000 species in the Convolvulaceae family, I. batatas is the only one that is widely used as food. Other plants in this family are sometimes eaten locally, like I. aquatica 'kangkong,' but many can be poisonous. The sweet potato belongs to the genus Ipomoea, which also includes beautiful garden flowers called morning glories. Some special kinds of sweet potatoes are grown just for their pretty flowers and are called tuberous morning glories. In North America, sweet potatoes are sometimes called yams, but they are not related to real yams, which come from a different plant family.

Description

The sweet potato is a leafy plant with vines that grow along the ground. Its leaves are triangle-shaped or lobed and can be green or sometimes purple. The plant makes pretty flowers, usually in shades of purple or lavender, that bloom when the days are short.

The part we eat is the tuberous root underneath the soil. It has smooth skin that can be yellow, orange, red, brown, purple, or beige. Inside, the flesh can be white, red, pink, violet, yellow, orange, or purple. Some types are sweeter than others, especially those with red or orange flesh.

Taxonomy

The sweet potato originates in South America, specifically in what is now Ecuador. People began to grow sweet potatoes in Central or South America at least 5,000 years ago. They likely spread from places like the Yucatán Peninsula in Mexico to the Caribbean and South America by the year 2500 BCE.

Sweet potatoes are closely related to a wild plant called I. trifida. Over many years, sweet potatoes changed and adapted naturally, making them a special kind of food crop.

Cultivation

See also: Sweet potato storage

Dispersal history

Long ago, before Europeans came to the Americas, people in Polynesia grew sweet potatoes. They spread the sweet potato by cutting pieces of the vine, not by using seeds. Scientists have found evidence that sweet potatoes were in the Cook Islands between 1210 and 1400 CE. Many believe that Polynesians brought sweet potatoes from South America back to Polynesia, spreading them to places like Easter Island, Hawaii, and New Zealand. Words for sweet potatoes in Polynesian languages and some South American languages are very similar, suggesting that people traveled between these places long ago.

Sweet potatoes reached Europe after explorers from Europe discovered the Americas. They were first written about in England in 1604. The sweet potato came to the Philippines during the time when Spain ruled the area. It was later brought to China around 1594 after a big crop failure. Sweet potatoes also became important in Japan in the early 1600s, helping to prevent hunger when rice crops failed. They were introduced to Korea in 1764 but did not succeed there.

Names

See also: List of sweet potato cultivars

Though sometimes called a "yam" in North America, the sweet potato is not the same as a yam. Yams are a different plant from a different plant family. The word "sweet potato" comes from the Taíno people of the Caribbean. Europeans mixed their word with another language's word for potato. In many places, sweet potatoes have different names. For example, in some South American countries they are called "batata," and in others "camote."

Habitat

Sweet potatoes grow best in warm places with plenty of sunshine and warm nights. They need about 750 to 1,000 mm of rain each year. These plants do not like cold frost and grow best around 24 °C (75 °F). They can be grown in many types of soil but do best in well-drained soil that is not too acidic or too alkaline. Sweet potatoes are usually grown from pieces of the vine rather than seeds. They are not troubled by many pests and can grow in poor soils with little fertilizer.

Depending on the type, sweet potatoes can be ready to harvest in two to nine months. In warm places, they can be grown as a summer crop. Sweet potatoes do not need many chemicals to grow and can be raised in many farming conditions. In the tropics, they can stay in the ground and be picked as needed, but in colder places they are usually harvested before frost.

Sweet potatoes are grown in tropical and warm temperate areas around the world where there is enough water. In the Caribbean, a type called "boniato" is grown, which has cream-colored flesh and is less sweet than other sweet potatoes.

Production

In 2020, the world produced about 89 million tonnes of sweet potatoes, with China producing more than half of that amount. Other big producers include Malawi, Tanzania, and Nigeria. Sweet potatoes are an important food crop, especially in developing countries. Scientists are working on creating types that can survive with less water to help with climate change.

Diseases

Main article: List of sweet potato diseases

Sweet potatoes can get sick with viruses and other plant diseases, which can make them look unhealthy and reduce their yield.

Uses

Nutrition

Cooked sweet potato (baked in skin) is 76% water, 21% carbohydrates, 2% protein, and contains negligible fat. In a 100-gram reference amount, baked sweet potato provides 359 kilojoules (86 kilocalories) of food energy, and rich contents of vitamin A (120%), vitamin C (24%), manganese (24%), and vitamin B6 (20%). It is a moderate source of some B vitamins and potassium. Between 50% and 90% of the sugar content is sucrose. Sweet potato leaves are edible and can be prepared like spinach or turnip greens.

Comparison to other food staples

The table below presents the relative performance of sweet potato to other staple foods on a dry weight basis to account for their different water contents. Sweet potato provides less edible energy and protein per unit weight than cereals, but it has higher nutrient density.

According to a study by the United Nations Food and Agriculture Organization, sweet potatoes are the most efficient staple food to grow in terms of farmland, yielding approximately 290,000 kilojoules per hectare daily.

Culinary

The starchy tuberous roots of the sweet potato are the most important product of the plant. In some tropical areas, the tubers are a staple food crop. The tuber is often cooked before consumption as this increases its nutrition and digestibility. The vines' tips and young leaves are edible as a green vegetable.

In Africa, sweet potatoes are used in various dishes. In northeastern Uganda, Amukeke (sun-dried slices of root) and inginyo (sun-dried crushed root) are staples. In West Africa, the young leaves and vine tips are widely consumed as a vegetable. In Kenya, sweet potatoes are used in modern recipes, including mashed forms and as flour in baked products. In Egypt, sweet potato tubers, known as batata, are a common street food, often baked and served with honey.

In Asia, roasted sweet potatoes are popular street food. In China and Korea, they are baked or roasted, often during winter. In Japan, roasted sweet potatoes are called yaki-imo. Sweet potato soup is served during winter in several Asian countries. In the Philippines, sweet potatoes, known as camote, are an important food crop, often boiled or baked and served with sugar or syrup.

In the United States, candied sweet potatoes and sweet potato casserole are traditional dishes, especially during Thanksgiving. Fried sweet potatoes and sweet potato fries are also popular.

In Oceania, Māori traditionally cooked sweet potatoes, known as kūmara, in earth ovens. In New Zealand, kūmara are widely available and often included in roast meals.

In Europe, sweet potatoes are used in various dishes. In Spain, they are called boniato and are traditionally served roasted during All Souls' Day.

In South America, sweet potatoes are used in dishes like ceviche in Peru and as a dessert called Dulce de batata in Argentina, Paraguay, and Uruguay.

Globally, sweet potatoes are used in modern sushi cuisine, with sweet potato rolls being a plant-based alternative to traditional fish-based rolls.

Molecular gastronomy

Freezing a sweet potato until solid, baking at a low temperature, then increasing to a high temperature brings out the sweetness by caramelizing converted sugars.

Ceramics

Ceramics modeled after sweet potatoes are often found in the Moche culture.

Dyes

In South America, the juice of red sweet potatoes is combined with lime juice to make a dye for cloth. Purple sweet potato color is also used as a natural food coloring.

Aquariums

Cuttings of sweet potato vine will rapidly form roots in water and grow, making them ideal for use in home aquariums.

Ornamentals

Ornamental sweet potatoes are popular landscape, container, and bedding plants. Grown as an annual in zones up to USDA hardiness Zone 9, they grow rapidly and spread quickly. Cultivars are available in many colors, such as green, yellow, and purple. Some ornamental varieties flower more than others. These ornamental cultivars are not poisonous, and although the leaves are edible, the tubers do not have a good taste.