I was asked a few days ago about clonal selection for a given varietal, Cabernet Sauvignon, and what difference it really makes in a final wine. My initial impression was that clonal selection of the cultivar(varietal) from a given site is not that important. However, after thinking about this for a day or so, I have a different point of view.
My initial thoughts were based on key assumption — the vineyard was planted with the exact perfect clonal selection and rootstocks for each block’s soil, weather, water and temperature conditions. This is a very large assumption on my part. It is nearly impossible to get the perfect match of clone, rootstock, capopy management, water regime, nutrient regime, etc the first time for a vineyard manager. There is a reason why it takes decades to determine the best varietals for a given area/vineyard, let alone a specific set of clones.
From a winemaking perspective, clonal selection is very important when a vineyard is young as some clones match up better with the specific growing conditions than others. Each clone is going to express different elements more boldly than other clones. Clonal differences such as cluster density and cluster size make a large difference in areas that have rain during the ripening season, heavy fog, etc — a loose cluster will be able to dry out more easily and have a lesser tendency to develop fungal issues than a tightly packaged cluster would be able to dry off. Each clone is going to bring different nuances to your finished wine.
For each wine, I have a particular style and flavor profile that I am looking for. I will try to select a mixture of clones when possible to give me more flavors / aromas / tannin profiles to work with for the final blend of the wine. It is the same concept as a painter wanting to have more shades of a autumn colors when painting an Autumn scene — more gradiations, great more depth and interest in the viewer. A wine from a selection of clones should have a more layered and complex profile than a wine from a single clone. If a specific clone gives you just what you are looking for, then fabulous — enjoy the great wine! If not, you will need to either make up for the missing element by blending in wine from another location or use some additional clones of the same varietal.
From a growers perspective, clonal selection is very important but for slightly different reasons. Clones are selected based on the easy of growing healthy grapes (cluster size, cluster density, flower period, degree of millerage, evenness of ripening), yield, heat tolerance, drought tolerance, etc. The type of grower makes a large difference on what elements they focus on — a bulk grower is selecting clones for highest yield, highest disease and fungus resistance, larger berry size; while a quality grower is looking for small berry size, low yields of highly concentrated berries, particular tannin profiles, rarity of the clone (premium value for a desired clone), etc.
Cabernet Sauvignon Clones (note all of this is subjective to each person’s palate and desired style):
Clone 7 according to Winemaker Phillip Corallo-Titus of Chappellet Winery: considered perfect match for our rocky, volcanic soils. The fruit it produces is valued for the rich, forward blackberry and casis flavors and balanced tanninns.
Clone 337 is considered to be one of the best selections for Napa Valley high-end wines. Yet, Clone 337 has shown some poor terroir results in Sonoma County hillsides if the cultivar was matched with the wrong rootstock and had low water availability. Clone 337 is considered to be quite fruity and has a depth of flavors.
Clone 7 is considered to be rustic (aka rough tannins) compared to Clone 337. Other say that Clone 7 is just fine when not grown on hillsides.
My conclusion is that clonal selection is very important for growing the best possible fruit for a given location with the realization that each person’s view of what is the best is subjective. Some combinations of specific clones on a given site will produce more concentrated and healthier fruit that others. If that combination produces grapes that suits your wine style, then you are a very happy grower/winemaker. If not, you need to either try another combination or look at a different location to grow/source your grapes from.