Sweet potato cultivation in Polynesia
[3] Sweet potato 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.
[6][7][8] Sweet potato became a major staple more so at the extremities of Polynesian culture – such as in pre-European contact Hawaii, Easter Island and New Zealand – than in central Polynesia.
[10] The presence of sweet potato in the Pacific is often cited as evidence of sporadic contact between Polynesian and Native American peoples.
[4] 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.
[24] 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.
[3] 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.
[3] One history involves Tūhoe ancestor Toi-kai-rākau, who, after he sailed the Horouta waka to New Zealand, introduced local Māori to dried kūmara (kao).
[30][31] Whakaotirangi experimented with ways to adapt growing kūmara in the colder climate, where they would develop an unpleasant sour taste when exposed to frost.
[34][35][36] 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.
[38][39] Other traditional cultivars outside of this list still exist, such as parapara (a variety used for medicinal reasons to feed the elderly, babies and the unwell), paukena (used to make kūmara kao), poporo, rekarawa and romanawa.
[25] By the mid-1800s, traditional rain-fed sweet potato cultivation in Hawaii ceased due to depopulation and damage caused by introduced Western grazing animals.
[44] Lithic mulching (mixing rocks into fertile soil) was used by traditional Rapa Nui gardeners in order to retain moisture in sweet potato plantations.
[44] Occasionally sweet potatoes were stored for festivals or ceremonies, by drying large tubers in the sun, then burying them in soil for up to one month.
[39] Kūmara and hue (Lagenaria siceraria, or bottle gourds) could be cultivated on about 45% of New Zealand, much greater than other traditional Polynesian crops brought to the islands, such as taro (Colocasia esculenta) and aute (the paper mulberry tree).
South of Taranaki and Hawke's Bay, kūmara was the dominant Polynesian crop plant (hue and taro were more commonly grown further north).
[9] Kūmara roots tend to develop fungal rot when daily temperatures fall below 10 °C, however this may have been mitigated by the use of internal fires and heated rocks.
[9] In spring, the flowering of the kōwhai tree and the call of the migratory pīpīwharauroa (shining bronze cuckoo) signalled when kūmara fields needed to be prepared,[45] but planting time varied annually, depending on whether a cold winter was predicted during Matariki.
[34][47] Māra kūmara (sweet potato gardens) consisted of puke (soil mounds) arranged in rows or a quincunx pattern of plants.
[45] However, crop rotation was much more difficult compared to other parts of Polynesia, due to tangled Pteridium esculentum (rarauhe, or bracken ferns) taking over the fallowing croplands.
[41][39] Māra kūmara are typically found on slanted, north-facing land, which attracts less moisture and is more sheltered from cold southerly winds.
[45] Layers of beach sand, cut grass and gravel were sometimes used for planting kūmara in August, with the insulation helping the tubers sprout faster.
[39] To combat this, fences were built around gardens to keep out pūkeko, while the caterpillars were either removed by hand, smoked out using kauri gum or kawakawa leaves, or by encouraging tamed seagulls to eat them.
[45] After harvesting, the tubers were placed in rua kūmara; subterranean pits with rectangular roofs, sterilised with fire and sealed with small wooden doors to keep out pests.
Kūmara were placed on shelves cut into the walls of the pit, and regularly checked for rot and rotated to ensure they stayed dry.
[51] Traditional eating methods include sun-drying smaller tubers (kao), grated (roroi kūmara), cooked in a hāngī, roasted and eaten with liquid from kina, or boiled.
[55] During the Classic period of Māori history when agriculture became more common, the areas where kūmara could grow the most successfully were often associated with more pā and greater population density.
[56][57] The potato could grow in colder climates, and was considered noa (not tapu, or needing sacred rituals), so could be grown by women or slaves.
[61] The Gocks donated stock of the new variety, called Owairaka Red, to farms in New Zealand's main kūmara-growing area around Dargaville and Ruawai in the 1960s, saving the crop from loss to black rot.
