Dry Farming in California's Drought, Part 3: How We Got Here (and Where We Go Next)

I was struck by a quote from Tegan Passalaqua, the winemaker at Turley, in a recent article on JancisRobinson.com.  In an interview with Alder Yarrow, Tegan said "In a Mediterranean climate like we have, vertical shoot positioning and 3 by 6 vineyard spacing is basically farming hydroponically".

Hydroponic farming, with its overtones of bland supermarket tomatoes, seems an unlikely candidate to provide the intensity and ripeness that a winemaker would expect from California.  But in its essence, that the farmer is providing everything that a plant needs to bear fruit, I don't think he's far off.  It's worth taking a few moments to understand how grapevines came to be so widely irrigated in California.  In the first part of this 3 part series, I looked at how our understanding of California's climate dictated changes versus what had been done in the Mediterranean.  In the second part, I detailed how we have been farming our vineyard since the beginning to wean it off of irrigation, and what changes we've made in recent years to adjust to the likelihood of a drier future.  In this third part, I will explore how viticulture evolved in California to rely so heavily on irrigation.  If you missed the earlier parts, this article will make more sense after you've read them.

According to Jancis Robinson¹, wine grapes were likely first domesticated from their wild progenitors somewhere near where modern-day Armenia, eastern Turkey, and north-western Iran meet, sometime before 4000 BC.  That area is a relatively arid climate, averaging around 400mm of rainfall per year (about 16 inches).  There, grapevines, along with similarly rugged crops like olive trees, were planted on dry, rocky hillsides where the more useful grain and vegetable crops couldn't survive.  This took advantage of grapevines' genetic predisposition to search out scarce water sources, delving dozens of feet deep if necessary.

By 2000 BC, wine grapes had been brought to areas around the eastern Mediterranean, including Egypt, Mesopotamia, southern Greece, Crete and the southern Balkans.  Expansion to areas north and west came over the next two millennia, brought by the exploring and colonizing Phoenicians, Greeks, and (later) Romans.  

High quality winemaking requires the concentration of flavors, achieved through stress on the grapevines and the maturity of fruit.  This happens naturally in the hot, dry climates where grapevines evolved.  But as viniculture moved north through Europe, into climates cooler and wetter than where wine grapes originated, the grapevines faced different challenges. Instead of not enough water, grapevines were challenged with too much water, threatening to dilute flavors.  And the cooler climes meant that lack of ripeness was a significant threat.  The solution to both these problems came in a new way of planting: spacing vines much more closely, so they competed against each other for the available water, and reducing the yield per vine so that the clusters ripened more rapidly.  For contrast, look at the differences in the old world.  An old vineyard in a warm Mediterranean climate (in the example below, Priorat, taken as a still from a promotional video on the Priorat DOQ Web site) might see grapevines three meters apart or more from their nearest neighbors (500 vines per acre, or less):

By contrast, a Burgundian vigneron in search of maximum concentration and character might plant grapevines as close together as one meter by one meter (over 4000 vines per acre), and reduce yields per vine from 20-30 clusters per vine to just 3 or 4.  The example below (from Wikimedia Commons) is of a vineyard near Gevrey-Chambertin, in Burgundy, where vines are so close together a tiny tractor can barely fit:

The net result is a can be a greater yield in tons per acre, with increased intensity and a better chance of getting the grapes ripe before the first frost.

It is perhaps useful to think of a grapevine as a small machine, whose roots act as pumps to wick water and nutrients out of the ground.  A vine's leaves absorb solar energy to power this machine. The water that is pulled from the ground is used during photosynthesis as the vine respires through the pores of the leaves, and is also trapped in the plant's tissues and fruit.  Planting more vines into a given plot of land requires more water for photosynthesis to be successful.  If there is enough (or too much) water, this extra density is beneficial and even important.  If there is not enough water, this extra density requires more irrigation to keep photosynthesis going.  And if irrigation becomes a major source of water for the vines, they change their root system to better capture that water source, growing more rootmass under the irrigation drips and less exploring deeper. 

So, is California's climate more like that of the Mediterranean, or more like that of Burgundy?  It depends on what you look at.  In terms of temperatures, you can find both, as evidenced by the success California's winemaking community has had with a a wide range of grapes, from the cool-loving Sauvignon Blanc and Pinot Noir (with origins in the north of France) to the late-ripening Grenache and Mourvedre (with origins in the hot, dry Spanish plateau).  But in terms of rainfall, it should be clear that except for perhaps in extreme north and coastal regions, our total precipitation more resembles the warmer, drier Mediterranean. In fact, many parts of California receive significantly less annual rainfall than the classic Mediterranean climate.  Relatively arid areas like Priorat receive more rainfall than most of the Central Coast, and the rainfall distribution in Paso Robles actually looks more like the Bekaa Valley in Lebanon than it does like Priorat, let alone anywhere in France.  The fact that we receive nearly all our precipitation in the six-month period between November and April only adds to the stress on the vines, and the need for planning if we're going to try to grow grapes without having them dependent upon regular irrigation.

You might wonder why plantings of grapevines in California look more like those in Northern Europe than they do like those of the Mediterranean.  That they do is a relatively recent phenomenon.  A paper on vine spacing presented to the American Society for Enology and Viticulture (ASEV) in 1999 by two winemakers from Robert Mondavi Winery makes for fascinating reading.  Before the late 1980's, most vineyards in California were planted at around 450 vines per acre.  The first large-scale (35 acre) high-density (2170 vines/acre) planting came in Oakville in 1985.  Since then, the paradigm has shifted rapidly, as winemakers found that they could translate the higher density into earlier-ripening, more reliably yielding crops of good intensity.

The downside? It hasn't seemed like there was much of one. More reliable yields, more reliable ripening, and increased intensity all seem like a good thing.  If I find that many of the wines that come from high-density irrigated plantings have a sameness, a fruit-driven thickness and relative lack of soil expression, this doesn't seem to be a complaint shared by many.  And separating out the preference for increasingly ripe flavors that developed over a similar timeframe is difficult (many connoisseurs of Bordeaux, where irrigation is prohibited, have described a similar development over the last two decades). But these higher-density crops can only survive in most parts of California through the regular application of irrigation.  When that irrigation water was cheaply and easily available, the fact that our natural rainfall distribution more resembles the Eastern Mediterranean than Burgundy or Bordeaux didn't seem to matter much. From an environmental standpoint, planting an irrigated vineyard was often a responsible choice for a farmer, as the high efficiency of drip irrigation and the relatively little water that grapevines need compared to a crop like alfalfa offered sustainability in both resource use and economics. But with all of California's agricultural communities engaging in a new level of soul-searching after four years of drought, it's clear to me that the calculus is changing.

Perhaps the solution for a drier future begins with a look at the past.  The old vineyards planted by immigrants in the 19th and early 20th centuries, many of which survived decades of neglect during prohibition and continue to produce a century later, were planted with the densities common to the warm Mediterranean climates (from where, of course, most of the settlers came).  Given our success in recent years replicating these older planting styles, I would hope that one benefit to come out of our current drought will be a renewed interest in low density plantings on deep-rooting rootstocks, requiring at most a fraction of the water of "modern" vineyards. That the wines have turned out to be so good is icing on the cake. 

It doesn't get more sustainable than that.

Footnotes
¹ Jancis Robinson's "Wine Grapes" (Penguin Books, 2012) is an incredible resource for anyone interested in the history or characteristics of different grape varieties.