Grapes have been grown successfully from New Zealand’s subtropical north (latitude 37°S) to the southern climes of Central Otago (latitude 45°S), where winters are harsh and summers hot. For wine production, grapevines need a cool period in winter, when the plants are dormant, and a warm period in summer and early autumn to ripen their fruit.
In most of New Zealand, spring and autumn frosts are always a possibility. Early autumn frosts can damage the grape crop just as it is ready for harvest, and late spring frosts can wipe out young shoots and flowers. In cool summers, grapes may not ripen properly, or fail to develop the sugar and flavour levels winemakers need.
Grape growers can limit frost damage by heating the air near their vines with diesel heaters, or spraying water over the plants. Helicopters or wind machines are used to mix warm upper air layers with the cool air at ground level. In spring and autumn, growers monitor the temperature each afternoon and request a helicopter to stand by if it looks as if a frost might develop.
Since 1970, grape producers have increasingly moved from warm, wet northern and western locations (around Auckland and the Waikato) to eastern and southern areas with hot, dry summers and autumns (Hawke’s Bay, Marlborough, Canterbury and Otago). The warm, humid summers of the western North Island encourage the growth of moulds that infect leaves and rot fruits.
Most eastern and southern vineyards require irrigation in summer.
Grapevines for quality wine production generally do best on freely draining, low-fertility soils. However, New Zealand vineyards are planted on many soil types – ranging from Northland’s heavy, water-retaining clay loams to the dry, stony silts of the Wairau Valley in Marlborough. In New Zealand, vines are grown on flat and gently sloping land at low altitudes – mostly with young soils of moderate to high fertility. This can lead to vigorous canopy growth at the expense of fruit production.