Feature article

Where can I grow grapes?

Example of a Suitability Index map (click to enlarge).

Searching for new land to grow your favourite crop typically means looking for localities with similar climate, soil, and topography to places where the crop is already grown successfully. This can be a time consuming and costly exercise.

New approaches to climate and soil modelling, funded by the Foundation for Research, Science & Technology, provide a desktop method to survey potentially suitable areas. The procedure doesn't eliminate the need to go out and investigate possible sites 'on the ground'. Its purpose is to rank the suitability of locations of interest, with high scores indicating where the most suitable areas are likely to be found, down to low scores where land has little suitability.

Grape growing localities

NIWA scientists examined the eight most extensive grape growing regions of New Zealand – Central Otago, Canterbury, Marlborough, Nelson, Wairarapa, Hawke’s Bay, Gisborne, and Auckland – to find out what makes these regions good for grape production. In each region, 23 climate, soil, and topographical features were extracted for the vineyard sites. We graded the range of values for each feature, and assigned high scores for the most favourable conditions. A combination of these scores was used to create a Similarity Index for grapes in each region – a high index for locations with many favourable features, and a low index where there were few favourable features.

Limiting thresholds

This is not to say that all areas with a high Similarity Index are going to be spot on for grape growing. That’s because each of the 23 variables is treated equally – i.e., there is no weighting of the scores based on the relative importance of the variable. It is quite possible that an area may have a high similarity score, but because the summer rainfall is too high (or some other feature crosses a limiting threshold) the area is completely unsuited to grape growing. The Similarity Index indicates areas which have similar climate, soil, and topography to some known grape-growing sites.

New locations

The Grape Similarity Index highlights areas near known vineyard locations that may be suitable for grapes, but can also be used to search for potentially suitable places further afield. For example, can grape varieties grown in Wairarapa also be grown in Manawatu?

Where can I grow grapes? is available on CD, including maps of the Suitability Index and a full explanation of how it is derived.

For more information, contact Andrew Tait on 0-4-386 0300, or email [email protected]

Acknowledgments: Soil data were provided by LandCare Research; topography data were obtained Land Information New Zealand