For someone like me who makes Bordeaux-varietal wines for a living, small, concentrated, fully ripe, thick-skinned berries are a thing of beauty. It takes just the right conditions to produce grapes like these, including drought-stressed vines that funnel their energy into their grapes rather than their leaves.
At 1,500-2,100 feet above the Napa Valley, Pahlmeyer’s Waters Ranch Vineyard is an amazing site with ideal sun and air exposure, slopes and soils. But in one section, the Cabernet Sauvignon vines have been too vigorous for my taste. Since the block is on a good slope, I had a thought: Why not induce drought?
Vintners now know that reducing irrigation forces vines to produce higher quality fruit, but we wanted to take it a step further and conserve water at the same time by laying tarps over the soil in the rainy months.
Although this method has been used in some orchards, none of the specialists I spoke with, including the researchers at UC Davis, had heard of trying it in a vineyard. They encouraged me to test the idea since there could be big implications for the wine industry.
After the season’s first five inches of rain, my crew and I laid protective tarps between the rows and connected them under the vines, ensuring there weren’t any gaps. We then placed sandbags on top of the tarps to prevent billowing and to slow the flow of rainwater. It took us about three days to cover the block’s 2.5 acres.
The rubber hit the road with our massive December rains. As hoped, water rushed down the “water slide,” into a drop inlet and into our silt pond. With millions of dollars being poured into water conservation research, this could be one idea for optimizing water resources.
We can't predict everything, of course. We worried that the tarps would damage our cover crops of native grasses and fescues, but it’s had the reverse effect. As if in a greenhouse, the grasses are growing like crazy. It's also warming the soil which may cause early bud-break resulting in a longer growing season for optimum flavors to develop.
In late April, we’ll remove the tarps. Come harvest, we’ll know a lot more about the experiment’s success or failure, and even more when the wines from this block are ready.