Sweet potato cultivation in Polynesia

Sweet potato cultivation in Polynesia as a crop began around 1000 AD in central Polynesia. The plant became a common food across the region, especially in Hawaii, Easter Island and New Zealand, where it became a staple food. By the 17th century in central Polynesia, traditional cultivars were being replaced with hardier and larger varieties from the Americas. Many traditional cultivars are still grown across Polynesia, but they are rare and are not widely commercially grown.
It is unknown how sweet potato began to be cultivated in the Pacific. Some scholars suggest that the presence of sweet potato in Polynesia is evidence of Polynesian contact with South America. However, some genetic studies of traditional cultivars suggest that sweet potato was first dispersed to Polynesia before human settlement.

History

The sweet potato plant is originally from the Americas, and became widely cultivated in Central and South America by 2500 BC. Sweet potato is thought to have been first grown as a food crop in central Polynesia around 1000–1100 AD, with the earliest archaeological evidence being fragments recovered from a single location on Mangaia in the southern Cook Islands, carbon dated between 988 and 1155 AD. Over the next few centuries, sweet potato was spread to the extremes of the Polynesian Triangle: Easter Island, Hawaii and New Zealand. Sweet potatoes may have spread so rapidly in the Pacific because Polynesian gardeners saw these plants as an improvement on already grown Dioscorea species, such as the purple yam. The plant was likely spread between Polynesian islands by vine cuttings rather than by seeds.
The prevailing theory for the lineages of sweet potato seen in Polynesia is the tripartite hypothesis developed in the 1950s and 1960s: that an original kumara lineage was brought from the west coast of South America circa 1000 AD, and later superseded by two lineages introduced by Spanish galleons and Portuguese traders circa 1500 AD, the Central American camote lineage and the Caribbean batata lineage. Sweet potato became a major staple more so at the extremities of Polynesian culturesuch as in pre-European contact Hawaii, Easter Island and New Zealandthan in central Polynesia. During the 1600s, traditional Polynesian cultivars of sweet potato and calabash began to be replaced with North American varieties. During reintroduction, the sweet potato had become entirely absent from many central Polynesian islands.

Pre-Columbian contact theory

Some researchers cite the presence of the sweet potato in the Pacific as evidence of sporadic contact between Polynesian and Native American peoples. However, it is unknown whether sweet potato was introduced through Polynesian canoes reaching South America, or by South American rafts visiting eastern Polynesian islands such as Rapa Nui. It is also possible that the plant was transferred without human contact, such as floating west across the ocean after being discarded from the cargo of a boat.
Genetic, cultural or linguistic links between Polynesian and Amerindian peoples such as the Chumash people of California, the Mapuche in central and southern Chile, and the Zenú, a pre-Columbian culture of Colombia, have been hypothesised. Dutch linguists and specialists in Amerindian languages Willem Adelaar and Pieter Muysken have suggested that the word for sweet potato is shared by Polynesian languages and languages of South America: Proto-Polynesian *kumala may be connected with Quechua and Aymara k'umar ~ k'umara. Adelaar and Muysken assert that the similarity in the word for sweet potato is proof of either incidental contact or sporadic contact between the Central Andes and Polynesia.

Natural dispersal theory

Some researchers suggest that sweet potatoes might have been present in Polynesia thousands of years before humans arrived there, arriving through avian dispersal or natural rafts. A 2018 genetic analysis of sweet potato collected from the Society Islands by Joseph Banks during the first voyage of James Cook in 1769 found this lineage diverged from South American varieties at least 111,500 years ago. The paper's authors also argued a natural dispersal was likely due to the presence of Ipomoea littoralis and Ipomoea tuboides in the Pacific and Asia — species which are related to American Ipomoea species that have similar seed morphology to sweet potatoes.

Regional introductions

Introduction to Hawaii

On the Hawaiian Islands, the earliest archaeological record of sweet potatoes is circa 1300 AD, where traces were found on traditional farmlands of Kohala, Hawaii. Sweet potato was likely introduced to the islands at a later point, after initial Polynesian settlers had arrived. Sweet potato was considered to be less superior or valuable compared to another crop on the islands, taro, but it was commonly grown as it could flourish in less favourable growing conditions, and only took between three and six months to mature.

Introduction to Easter Island

Introduction to New Zealand

Sweet potato is a traditional crop for Māori. Archaeological evidence suggests that kūmara arrived in New Zealand after the original Polynesian voyagers had settled in New Zealand, likely sometime between 1300 and 1400. Lack of archaeological evidence on the abandoned Māori settlements on Raoul Island and Norfolk Island implies kūmara was not available in the early 1300s. Oral histories tell of a return voyage to central Polynesia to collect the plant for use in New Zealand, but oral histories do not agree on a single voyage or source: the introduction of kūmara is associated with the Aotea, Arawa, Horouta, Kurahaupō, Māhuhu, Māmari, Mātaatua, Tainui and Tokomaru canoes, possibly due to the Mana associated with having brought kūmara to New Zealand. One history involves Tūhoe ancestor Toi-kai-rākau, who, after he sailed the Horouta waka to New Zealand, introduced local Māori to dried kūmara. The locals, having loved the vegetable, sailed on the Horouta back to central Polynesia to collect the plant to grow in New Zealand. Ngāti Awa have a similar stories about the Mātaatua waka, that it was sent to bring kūmara supplies to Whakatāne. In Tainui and Te Arawa traditions, kūmara was brought to New Zealand by Whakaotirangi, a woman who carried seeds of important plants on the journey to New Zealand after being kidnapped by the chief Tama-te-kapua, around 1350 AD. Whakaotirangi experimented with ways to adapt growing kūmara in the colder climate, where they would develop an unpleasant sour taste when exposed to frost. Another history involves Marama, the junior wife of Hoturoa aboard the Tainui waka. She brought kūmara plants with her on her journey, but, when she arrived in Aotearoa, she was unfaithful to Hoturoa with a slave. As punishment, her kūmara plants turned into pōhue a traditional weed of kūmara farms.
In 1880, botanist and missionary William Colenso listed 48 varieties grown in Northland, Hawke's Bay and the East Coast. These traditional varieties came in a variety of colours, shapes and differing rough/smooth textures. Northland Māori described a red-fleshed, red-skinned variety called paikaraka as the oldest variety of kūmara to Colenso, while Te Arawa iwi sources in the 1940s called toroa-māhoe and hutihuti the oldest varieties. Kūmara does not seed in New Zealand due to the climate, meaning mutations in buds and careful cultivation of these plants likely led to the new varieties. A 1955–1959 survey of Māori farmers identified four cultivars considered to be pre-European: taputini and houhere, and two closely related varieties grown across the North Island: rekamaroa and hutihuti
. A 1997 DNA analysis of these varieties confirmed that taputini, rekamaroa and hutihuti are all pre-European. Other traditional cultivars outside of this list still exist, such as parapara, paukena, poporo, rekarawa and romanawa.

Cultivation and use

Hawaii

Sweet potato on the Hawaiian islands was typically grown in makaili, and in arid/coastal areas. Many māla were planted as a mix of sugarcane and sweet potato, with sugarcane planted in rows alongside the stone field walls to act as a windbreak for the sweet potato crop planted in between these rows. Often sweet potato was planted in mounds, with the soil mulched with a mix of rocks and plants. Rats preyed on the sweet potato crops during the Hawaiian rainy season, while periodic outbreaks of Sphingidae moth caterpillars, cutworms and weevils would greatly damage crops. Sweet potato is associated with the new year festival of italics=unset, where the first fruits of the harvest were offered to the gods, typically sweet potatoes and taro.
By the mid-1800s, traditional rain-fed sweet potato cultivation in Hawaii ceased due to depopulation and damage caused by introduced Western grazing animals. Since the early 1900s, pests were introduced to the islands which impacted farmers' abilities to grow sweet potato in Hawaii, such as Cylas formicarius and Omphisa anastomosalis. This is to the degree that farmers often refrain from planting sweet potato in the same location for two successive seasons. Sweet potato became a major export crop for Hawaii in the 20th century, although since the 1990s the number of plantations has decreased.
There are over 300 different names for traditional sweet potato varieties, with many names likely being synonyms for the same varieties. Some of the most commonly cited in ethnographies and traditional sources include apo, huamoa, kawelo, likolehua and uahi-a-pele. Huamoa is a variety described as egg-like, being round, with a white skin and a yellow flesh. Most sweet potatoes produced in Hawaii are modern imported varieties, such as the Okinawa purple variety, however several heritage cultivars that are still grown are likely pre-European cultivars, including, and purple.