Scientific knowledge and canopy management
As well as innovative technology, science has played a distinctive role in the transformation of New Zealand’s vineyards. Lacking the long European empirical experience, grape growers and winemakers sought, and have been provided with, local viticultural research. They have also advanced this knowledge themselves. Whereas in the French industry the quality and reputation of wines provide a certainty that their viticulture is working, New Zealand growers have benefited from theoretical and empirical research that has improved their understanding of their new environments. The research on canopy management of the mid- to late 1980s was especially important in empowering
Lack of competition between vines in these widely spaced rows in the Hawke’s Bay encouraged thick hedges, shaded grapes, and slow ripening.
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Marti Friedlander, Auckland War Memorial Museum grape growers to understand quality viticulture and use these principles to advance it. Successful experiments that reduce the vigour of vines by inter-row planting of suitable cover crops, while simultaneously reducing pest problems, is promising. So is work on the biological control of diseases such as Botrytis cinerea. Winemaking knowledge, which tends to be less regionally specific, has been augmented by formal training, local sharing of knowledge in the close-knit wine communities, and regular (often annual) experience in other countries.
Between 1960 and 1980, three aspects of viticulture were limiting New Zealand’s ability to produce the best-quality fruit to make fine table wines. First, the vinifera stock were heavily virus infected. Second, suitable clones for New Zealand conditions were not available for all varieties. Third, knowledge of methods of canopy management was limited. All three deficiencies were progressively ameliorated during the next three decades so that New Zealand’s potential for growing grapes to make fine wine was realised.
Canopy management is the shorthand phrase for the trellising of the vine and the training and trimming of its leaves to maximise its ability to photosynthesise and produce grapes of optimum quality for making wines of high quality. The scientific programme that was carried out during the 1980s to advance canopy management in New Zealand viticulture was particularly important. One individual, Richard Smart, was especially influential. An Australian plant physiologist and microclimatologist with a PhD from Cornell, one of his scientific interests was the trellising system for the vine and the way that this influenced its microclimate and ability to ripen its fruit. In viticultural studies the microclimate is usually defined as the climate within the canopy – the atmospheric conditions that directly influence the vine’s leaves, fruit and roots. Smart and other scientists had modelled the effects of temperature and sunlight on berries and the photosynthesis of leaves, the influence of orientation of rows, and the impact of the width of the vine ‘hedge’ on the ripening of grapes. The architecture of the pruned vine affects the arrangement of the leaves and their ability to photosynthesise effectively. Smart demonstrated that when the hedge of vines was thick the interior leaves functioned at less than 5 per cent of their potential. Mildews were also difficult to control in the interior leaves. Grape growers were converted to the thin canopies that he advocated.
Smart went one stage further by designing and experimenting with different trellising systems, several of which proved to be highly efficient. When he returned to Australia to become an international viticultural consultant, he was disappointed that these efficient trellising systems had not been taken up more widely as had the Scott-Henry system in Oregon and internationally. Nevertheless, his influence on New Zealand viticulture was profound. In field days, seminars and conferences his knowledge and enthusiasm for effective canopy management was infectious and was transferred to the new generation of viticulturists. Regardless of the trellising system being used, grape growers and winemakers became acutely aware of the principles underlying the management of the canopy. Cumulatively, Smart’s work demonstrated that in the cool climates of New Zealand it was possible to ripen the chosen varieties of Vitis vinifera in most seasons.
These scientific results are not surprising given the practices that have been evolved empirically in regions such as Burgundy. There, as in many of the prestigious regions of France, vignerons achieve low vigour by having the vines closely spaced (1 m by 90 cm) and practising a regular programme of leaf plucking and vine trimming. Smart’s work established the science behind these practices and was widely publicised and discussed both locally and internationally. His greatest influence was not in the wholesale adoption of a particular type of supporting trellis but in raising the general level of understanding of the importance of balancing grape crop with vine vigour – something that can be achieved in a variety of ways on a variety of trellising systems. There is no doubt that New Zealand grape growers are much more aware of the importance of the ratio of leaf area to crop and are now adept at producing fruit of optimal quality for making wine from grapes grown in different environments.
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