In February 2014 the research team returned to Tamewhera, on the north west coast of Ahuahu Great Mercury Island. The initial stage of fieldwork focused on surveying the large-scale garden features and related living areas which had been identified in 2013.
The visit was an opportunity to introduce the Stage III and BA Honours students enrolled in the Archaeology Field School, run by the Department of Anthropology at The University of Auckland, to excavation methodology and practical archaeology.
The archaeological landscape
Steep slopes surround the valley at Tamewhera. A large, impressive pa at the entrance to the valley has a number of kūmara storage pits and stone-faced living terraces on the very steep slopes. The interior of the pa (fortified site) is well protected by steep slopes and vertical cliffs on the seaward side.
On the north facing slope of the valley there is a large Māori garden complex of about seven hectares where andesitic basalt outcrops as surface boulders. Constructed stone row alignments run down the slope, ending at the edge of the large swamp. Groups of alignments on different orientations suggest parts of the garden were made at different times, and what we see today is the end product of many uses of the area. Alongside these features there were also stone-faced terraces where Māori lived while tending their gardens.
The gardens at Tamewhera would not be out of place elsewhere in Polynesia where stonework was commonly used to mark boundaries between gardens, and to retain soil on sloping ground.
Horticulture on Ahuahu Great Mercury Island
The climate of New Zealand is very different to that of tropical Polynesia and the Polynesian settlers had to experiment with where crops could be grown, and how best to grow tropical kūmara plants in the cooler climate.
In Polynesia kūmara can be grown all year round but in New Zealand the tubers are harvested in autumn. Pit storage was developed to keep kūmara tubers at a steady temperature and humidity for months over the winter period. This was especially important for the seed kūmara which were required for the next spring planting.
Kūmara was the main crop grown on Ahuahu, but other food crops such as taro, yam and gourd were probably also grown. Yam was apparently more difficult to grow as it requires warm soil temperatures, and a longer growing season than is available over most of the climatic regions of New Zealand. Taro may have been grown in damp areas such as on the edge of the Tamewhera swamp.
There are a number of Māori gardens on Ahuahu which use stonework. Elsewhere on the island land without stones was also used for gardens but very little surface evidence remains. In one valley there are shallow channels at regular intervals on the valley floor and surrounding slopes suggesting that in the absence of stone, garden boundaries were made by other means.
The island has a warmer climate than the mainland and the elevated temperature would have been important to the Māori gardeners on Ahuahu, who needed their kūmara crop to fully mature by late summer or autumn. This favourable climate may have made Ahuahu the preferred location for agriculture over the adjacent mainland. There are oral traditions referring to Ahuahu as the homeland of kūmara, suggesting the island may have played an important role in distributing kūmara tubers after Polynesian settlement.
Surveying the gardens
The large size of the garden at Tamewhera made it difficult to detect patterns of alignments and terraces on the ground. A team walked up and down the slope using handheld Trimble GPS units to map the rows and build up a plan of the garden site. Later, the data was downloaded into GIS (Geographic Information System) software, which captures the location information about the individual places of Māori occupation on the island, and the location of stone artefacts and samples within each site.
The team also used a Leica scanner to create a three-dimensional image of the valley landform and the garden features within it. The data from the scanner can be integrated with the GPS map of features to better understand how topography and slope influenced the position and shape of the garden area.
Next time: Living and working in the gardens
Check back for the next report in this series where we look at different parts of the garden area and the excavation of several terraces which revealed a house and temporary shelters.
Ngā tupu mai i Hawaiki – plants from Polynesia
When the ancestors of Māori crossed the ocean to New Zealand, they brought plants from Polynesia to cultivate in their new home. Kūmara (sweet potato) became a staple food, and hue (gourds) were used to store water and food. But other plants did less well in the cooler climate.
Read the full story by Louise Furey on Te Ara – The Encyclopedia of New Zealand