Where’d the Water Go? (or how deep is that bucket anyway?)
Gazing at my Carte Géologique de l’Hermitage, with its rainbow of hues signifying 12 soil types organized into three main epochal groups, I marvel at the adaptability of Syrah, its chameleon-like ability to express a delicious range of flavors. Hermitage is unusual due to the variety of her soils, an accident of geology and history. In the course of its southward progress, the Rhône River makes an eastward jog, creating one of the few southward facing hillsides along the northern length of the river. Hence, vintners of yore were blessed with reliable ripening, yet a variety of Syrah expression due to the varied soil on the slope of the hill. This became evident to me a few years back when I tasted through seven of the lieux-dits with Jean-Louis Chave. What is it about soil that may effect the vine and resulting wine in Hermitage as well as in my vineyard?
Just now when I look down the spine of the hill at our block two Syrah, the far end of the rows cresting on higher ground offer me insight for an explanation. I wonder what on earth is going on in the soil, say, five to ten feet down, that causes the vines on the end to still show relatively unchecked vegetative vigor while the rest of the block is filled with more sensibly minded, just-thinking-about-starting-veraison siblings. For the sensible vines, shoot elongation has stopped. Tendrils are drying up and falling off in a progression from shoot base to shoot tip. The shoots are becoming woody – turning from green to brown – in the same direction as the tendril desiccation. Fruit flavor ripening is in full swing. Why are these hilltop vines still growing when they’ve been given the same amount of water up to this point (none) and are in similar soils? I find little sections like this in the various blocks of Syrah, though they by no means constitute a significant portion of the vineyard. I begin watering by the onset of veraison and to accommodate the few unruly vines still in a state of vegetative growth, I resort to plumbing around them, bypassing them altogether, resulting in the first truly dry-farmed vines on this property. Is this a problem? What is going on here and what does this tell me about soil and wine quality?
One main difference between Hermitage and Peay Vineyards is summer rainfall. While we had some lingering bouts of spring showers this year, and on occasion receive autumn previews of the winter to come (usually a special delivery of the “pineapple express”), we really don’t get any summer rainfall. Hermitage, however, receives a few inches in each month of June, July, and August. In years when the usually reliable summer rainfall fails to show up for a month or two (2003 and 1997, if I remember correctly), a bit of hand wringing is all that French law allows as plant growth and fruit maturation will halt and, if prolonged, the berries will begin to shrivel. This, though, is the most dire of pictures, since the old age of much of the Hermitage vines buffers against short periods of drought by providing a pool of resources to mitigate the conditions, at least for a short period of time.
Further assistance to dry-farmed vines can come from a permanent aquifer for the roots to draw upon; a water table some distance beneath the surface of the soil that the roots can access. Les Gréffieux and Les Diognieères, the bottom two lieux-dits of Hermitage, grow upon recent alluvial soils and consist of deeper soils much closer in elevation to the river, close enough that the ever-searching roots (which can grow downwards over twenty feet) might be able to access a permanently wet soil horizon. Over eons, rivers cut into the earth leaving alluvial benchland perched along sides of river valleys. Some of the best dry-farmed old Zinfandel is planted in the Dry Creek and Russian River Valleys on this benchland. In the flatlands south of Windsor, water wells need only be twenty feet deep. Older benches can be perched above the water table so high that dry farming is not possible. Being alluvial, they are easily penetrated by vine roots but for the same reason, are extremely well-draining.
Water holding capacity then is another factor to consider. Some of the first noteworthy plantings of Pinot noir in the Red Hills of Oregon’s Willamette Valley were and are still dry-farmed. These “Jory” soils are basaltic, roughly nine feet deep, and can hang on to the water from the heavy winter rains to such an extent that the happy plant with its verdant growth has a hard time getting the signal that it’s time to start veraison, to switch over from green growth to fruit ripening. Meanwhile, neighbors planted on “Willakenzie” soils, or Jory soils of only two feet in depth (the Eola Hills), find their vines making the transition to ripening earlier, and some growers are discovering the benefits, sometimes with the gentle prodding of wine makers, of drip irrigation. The basalt of the Red Hills, the limestone of the Côte D’Or, and to some extent, the sandstone at the deeper depths of our Ohlson Ranch soil series all have hydrophilic properties, an affinity which allows them to hold onto water longer. In all three cases, however, the soils are elevated causing gravity to pull the water deeper and away at rates varying with the soils’ relative affinities, forcing the roots to chase the water deeper.
Before we planted our vines, we dug a dozen backhoe pits to perform soil analysis and visually assay the soil horizons. Because of the way the soil was deposited during the Pliocene epoch before being uplifted, we found great homogeneity between pits: fine silty sandy loam, with a varying degree of clay – 15 to 25%, underlain by more compacted material which became a relatively dense sandstone. This sandstone layer is usually four or five feet deep, but occasionally only three feet deep. In some cases we found fractures in the sandstone, some lined with iron, indicating water, and it is at these locations that I now see those Syrah vines that lag behind their siblings in making the transition from vegetative growth to ripening.
If that sandstone proves to be impenetrable for any of my vines, I will need to water them in August for the duration of their lives. This idea was represented to me once as growing grapes in a bucket – the bottom of the bucket being the bottom of your rooting zone. The nutrient content and water retention characteristics of that bucket are what the earth provides and I, the farmer, supply anything else that is needed. The slow steady drainage of the moisture from our winter rain-saturated soils coincides nicely with the seasonal growth phases of our vines. Spring growth is vigorous, early summer sees a slowing and by veraison vegetative growth is over. I suspect that over time, the roots will exploit tiny fissures and burrow into the sandstone, accessing a little more moisture, and reducing the amount of post-veraison irrigation water necessary.
Studies of water stress and resulting wine quality indicate that some stress is a good thing and that the timing of the stress is important. Therefore, the timing of the draining away of winter water is a key element for quality grape growing, and dry-farmed grapes that see too much water will never produce as interesting fruit (and wine). On the other hand, if there is too little or no water the vine will crash and the fruit will desiccate without truly ripening.
Our few unruly vines catch up and appear much the same as their siblings by harvest, albeit with larger clusters, due to the delay in the stress timing. We may find ourselves culling that fruit, fermenting it separately to evaluate it, and ultimately, eliminating those vines. Perhaps they should return to being patches of wild irises?