Cultigens grown by Māori
When Europeans arrived in New Zealand, six introduced cultigens (cultivated plants that have no known wild ancestor) were being grown by Māori. They were:
- kūmara (sweet potato, Ipomoea batatas)
- hue (bottle gourd, Lagenaria siceraria)
- aute (paper mulberry, Broussonetia papyrifera)
- taro (Colocasia esulenta)
- uwhi (yam, Dioscorea species)
- tī pore (Pacific cabbage tree, Cordyline fruticosa).
These plants were brought from Polynesia by the ancestors of Māori when they arrived in New Zealand from around 1250–1300 AD. Other food crops, such as arrowroot, banana, breadfruit, coconut and sugar cane, may also have arrived on the voyaging canoes, but could not be grown in the new country’s cooler climate. Some plants may have been introduced to New Zealand more than once, possibly coming from different island groups.
Cultigens in the Pacific
Polynesians cultivated a number of plants which their ancestors had taken eastwards across the Pacific from Asia. Taro was most commonly grown on islands with a high rainfall, like Samoa. Yams fared better in places with separate wet and dry seasons, like Tonga. Breadfruit and bananas were the main crop in the Marquesas Islands and southern Cook Islands.
Polynesians linked the calendar year and rituals to the annual growth cycles of these crops.
Evidence of early Māori gardening remains as microfossils in the soil. These include pollen, starch grains and phytoliths (minute silica deposits present in plant stems). Micro-remains help scientists identify where different plants were grown. Pollen from hue, and possibly from aute, has been found in soil. Starch grains and xylem (water-carrying tissue) cells from kūmara have been detected in a number of soils and storage pits, and taro and yam starch grains have been found in Northland.
Unlike the Polynesians’ other cultigens, kūmara is indigenous to South America and did not come across the Pacific from the west. Archaeological research on the settlement of Polynesian island groups and their horticultural history points to kūmara arriving in Polynesia between 900 and 1100 AD. The seafaring Polynesians had large, double-hulled sailing canoes, and the navigating skills and ability to travel across large areas of ocean from one island group to another. It seems likely that some travelled to South America, and returned to Polynesia with kūmara.
There were a number of domesticated crop plants in South America, so the question of why the Polynesian visitors chose kūmara to take home is intriguing. Archaeologist Helen Leach has suggested that kūmara was adopted because of the similarity of its leaf shape and tubers to the yam (already grown in Polynesia). Unlike yams, however, kūmara could be grown year-round, and could be reproduced by planting rooted cuttings instead of tubers.
Kūmara was a minor crop on most islands – it became the dominant crop only on Rapa Nui (Easter Island) and in New Zealand. Growing practices and rituals associated with yams were transferred to kūmara.
Linguistics and archaeology suggest that the Society Islands, or Mangaia in the Cook Islands, may have been the source of the kūmara varieties brought to New Zealand.
Hue (bottle gourds) were once believed to have originated in South America. But DNA research in the early 2000s suggests that the gourds grown in Polynesia and New Zealand are a hybrid of American and Asian species. Scientists think that gourds were either deliberately introduced from Asia and America, or may have floated across the sea to Polynesia and then been grown from the seeds inside.
Adapting to New Zealand
In Polynesia, it was common to plant kūmara and yams on mounds. Gourds and taro were grown in shallow hollows to retain moisture. Polynesians built stone walls and rows for shelter and as boundaries around the gardens. They also used fences and shallow ditches.
These methods were brought to New Zealand, where the Polynesian colonists quickly learned to adapt their planting regimes and techniques to the cooler climate. The growing season was restricted to the warmer months, and they added coarse sand and gravel to soil – probably to improve drainage, increase the temperature and extend the period of plant growth. This was particularly important from Marlborough south to Banks Peninsula (the southern limit of kūmara growing).