Now that the new growing season has started again, I think about all the factors which contribute to the taste of grapes. We have had an unusually rainy winter which means that there is plenty of water for the roots over the coming months. That is good news since we want the vines to get the water from below once they start flowering.
The vines need just the right amount of water throughout the season. During ripening it is important that the vine never goes completely dry and leaves start drooping. The vine needs to use its energy to ripen the grape not just trying to survive. A little water stress tends to bring out more intense flavors, but too little water stresses the vine to shut down, stop producing sugars and we get immature grapes with less desirable flavors.
This is where the composition of soil comes in. If the soil can hold water for longer times the water from above will come to better use. Silt and clay hold water better then sandy soils and gravel loam also has decent water holding potential. Our steep hillside where the Cabernet grows is a red mineral rich clay which holds water well which is essential since water runs off a hill faster than on the valley floor. Our Cabernet grapes struggle more to get the water out of the ground and there is less of it. On the valley floor our gravel clay loam is deeper and holds water quite well. We also enhance the water holding property of the soil by growing cover crop which brings a number of other advantages as well. Besides holding water, it aerates the soil through the many tiny root holes and it bring additional organic matter to the soil.
The amount of sun also makes a huge difference to taste. Too much sun and there is an overly jammy flavor to the wine but too little can bring less desirable green vegetable flavors for example. We get more sun on our Cabernet grapes since they grow higher up and the fog primarily is below them in the morning. Our white grapes grow on the valley floor and get needed shade and cooling at night and morning when the fog lingers low in the valley. If you have too much sun one way of controlling that is through pruning the canopy of leaves so just enough sun filters through to the grapes. That is how we control the sun on our Cabernet grapes by making sure there are enough leaves allowing for sun dappled light to shine through.