Rod Byers; California grape vines, surviving or thriving?
Special to The Union
Lately I have been asked about how California’s ongoing drought is affecting grapevines. I have often said that the first two words to the answer to any wine question are always the same: it depends.
The answer to the drought question is no different.
First, it is important to point out that grapevines are among the world’s greatest drought-tolerant plants. Plant them in rich soil with lots of water and they do not perform as well as if they are planted in poor soils with limited water.
That is why the traditional European pattern has been to plant wine grapes where other crops struggle, often on thin-soiled hillsides, reserving the richer valley floors for more demanding crops.
In spite of Spain’s recent loosening of its wine laws to allow vineyard irrigation, irrigating vineyards in Europe’s fine wine regions is illegal. It has always been their position that watering vineyards decreases quality by increasing quantity.
The question of irrigation is no small matter. In France, the natural delivery of water to vineyards is at the core of one of their most cherished beliefs, that of terroir.
The French think of terroir as the combination of natural forces that make one vineyard site superior to another, even when the vineyards are adjacent to one another.
While there are many elements including temperature, wind, or degree and aspect of slope that create a vineyard’s terroir, drainage is among the most important.
The gradual depletion of available water throughout the summer growing season is essential to producing fine wine grapes. The best sites are the ones that do this naturally, and do it better than their neighbors.
Give a grapevine unlimited water and rich soil and all it will do is generate leafy vegetation. When conditions become less favorable, they strive for reproduction, which means grape production. One of the prime stressors to trigger fruit production is the depletion of available water.
It is estimated that a typical vine needs between 25 and 35 inches of water throughout the growing season. In France, where summer rains are common, good drainage is critical. It is also why arid regions can’t support viticulture.
Growing grapes without supplying additional water is called dry farming. Because Europeans brought their grape-growing practices with them, dry farming became the practice in California’s early vineyards as well.
In the last quarter of the 19th century when California experienced its first brush with worldwide wine acclaim, the vineyards of Sonoma and Napa were dry farmed.
All of Napa was dry farmed until the 1960s when growers started using overhead sprinklers, although at first it was primarily for frost control. Drip irrigation arrived on the scene in the 1970s just as California was beginning its second wine renaissance.
The drought of 1976-77 no doubt encouraged the use of drip in the many new vineyard plantings at the time.
With drip, the benefits for the grower include reliability and increased yields. It allows for a consistency of style that dry farming, subject to the vagaries of each year’s weather, cannot deliver.
By being able to supply water through long tubes with emitters to individual plants, drip irrigation also opened vast new territories that had previously been too arid for viticulture. Australia, the world’s most arid continent, was a huge beneficiary of drip technology. Yellow Tail wouldn’t exist without it.
Now the vast majority of new world vineyards, from New Zealand to California, are on a drip system. It is the exception to find a dry-farmed vineyard. In addition to being an effective delivery technique, drip systems allow growers to deliver precise amounts of water to different areas of the vineyard to keep the vines stressed but not too stressed. It is the biggest manipulative tool a grower has.
Drip irrigating promotes root growth closer to the surface, which is why turning the water on or off has such a dramatic effect. Dry-farmed grapevine roots dive deep, with some growers claiming as much as 40 feet, in their pursuit of underground water. Whether they are using a drip system or dry farming, premium wine producers restrict yields in order to make a superior product and that cost is already reflected in the price of their wine.
But not so at the low end. In order to meet the economies of scale to produce inexpensive wine at the highly competitive lower end of the market, California’s Central Valley growers need to produce 10 to 15 tons to the acre.
They use irrigation to plump up their grapes like balloons full of water. If shortages continue, or water simply gets more expensive, expect low-end wine prices to increase. If drought conditions continue in California, more growers will consider dry farming as a method of survival. While still small, interest in new vineyards intended for dry farming is on the increase.
Tablas Creek Winery in Paso Robles dry farms their 120-acre site in spite of the average rainfall being less than 15 inches per year, and less than 10 in the last two years. The vine roots find the rest of the water they need themselves and the winery thinks the grapes are better off for the struggle and would dry farm even with unlimited water.
Perhaps its a case of déja vu all over again as we return to historic methods of grape production and the grape vine proves once again why it is the greatest drought-tolerant plant of all and why California will never be without wine.
Rod Byers, CWE, is a Certified Wine Educator and wine writer as well as a California State Certified Wine Judge. You can find information about his summer Sierra College Wine Classes at http://www.pinehillwineworks.com and he can be reached at 530-802-7172.
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