Ahumāra - Māori horticulture

The first Māori immigrants, who came from much warmer climes in the Pacific, were forced to adapt their horticultural methods quickly in order to survive. Kūmara, in particular, required a long, warm season, making it a marginal crop in Te Tau Ihu. Māori developed a taste for local fernroot to supplement their carbohydrate requirements, and learned to modify soils for the safe and most efficient production of kūmara and other crops.

The Maori gravel soil of Waimea West, Nelson, New Zealand. The Nelson Provincial Museum
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Early tribes, like Waitaha and Rapuwai, established large cultivations which can still be identified. Many gardens, positioned to exploit the best possible aspect for sunlight and shelter, have been found in the Marlborough Sounds. The natural soil fertility of these sites has often been enhanced – in both structure and chemical composition – through the addition of vegetable matter, wood ash, sand and fine gravel. The remains of other features, like elaborate terracing, stone walling and pathways, are still quite clear at Titirangi on the southern coast of Te Moana Raukawa (Cook Strait).

On the Waimea Plains near Nelson, more than 400 hectares of soils have been altered by the addition of enormous quantities of wood ash and hundreds of cubic metres of sand and gravel. Large borrow pits up to two metres deep, from which the gardeners had made very selective extraction of gravel sizes, can clearly be seen today. Organic materials found in one of these pits have been radio-carbon dated at between 1460 and 1650 AD, and shells found at the occupation site near Appleby School have similar dates, although the ‘…Appleby site was sitting on garden soils’,¹ implying that the gardens themselves are even older.

Geological map of the Province of Nelson Dr F. von Hochstetter and J. Haast, 1860 - J. Perthes, Auckland City Library, Special Collections, NZ Map 5694e 
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These ancient Māori garden sites have long been recognised as the most fertile soils on the Waimea Plains. Even after sixty years of European cultivation, farmers in the 1920s who were situated on the ‘Māori soils’, required only a fraction of the added phosphate, potash and lime needed on the neighbouring ‘natural’ soils. The enhanced fertility is accounted for, not just by the burning off of the original forest which had been growing on these lands, but by generations of repeated ash deposits obtained by burning ‘imported’ timber – driftwood from the nearby Waimea River and Estuary and from the forests growing on the adjacent river flats and on the Moutere Hills, some one to two kilometres distant.

The Waimea Plains and cultivated country near Nelson / John Gully
Alexander Turnbull Library, PUBL-0010-08
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It is because of the added gravels, that the soils of these old Waitaha gardens also drain much more freely and, being almost black, the heat absorption is much greater. The predominance of large flat stones in the upper soil layers indicates that the gardeners placed a stone mulch around the crops to further enhance absorption of solar heat during the day, for slow release during the cool nights. All of these factors combined to enable ancestral Māori to grow to maturity crops, such as kūmara, for which the local growing season was otherwise too short and the climate too temperate.

With the arrival of whalers in Marlborough, and colonial settlers in Nelson, Māori quickly adapted their horticultural skills and gardens to exploit new markets for potatoes, corn and other introduced crops.

2008 

Updated April 2020

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