There has historically been a perceived link between soils that vines are grown in and the flavour of the wine that you drink. However, there has been quite a lot of research into the subject in the last few years and there is very little scientific evidence to prove any link. The French word “Terroir” expresses their fondness for the uniqueness of each and every vineyard in France. They are firm believers in a link between the vineyard and the final wine. The French are very keen to point out that their wines express the unique place that they come from. This is the whole basis of their “Appellation” system. We are also familiar with descriptions of wines that bear a relation to the soils that the wines come from, “flinty and minerally” flavours for Chablis, for instance. These geological metaphors bolster our opinion that rocks are important.
The most important factor in a vineyard’s geology is the water supply. This is key to the vine’s survival and key to the vine’s production of ripe and healthy grapes. The nutrients that are dissolved in the water absorbed by the plant are also critical to the plants survival, but do they actually contribute to the flavours in the grapes? I’m afraid that research says that they really don’t. Rocks don’t weather fast enough, and even if they did, the plant would still only absorb what it wanted for survival. Water supply is frequently manipulated to suit wine production. This can be irrigation in arid areas or drainage in wetter ones. It has been shown that underlying geology doesn’t affect flavour nearly as much as dissolved organic matter in the soils. So, wines taste more of rotting vegetation than rocks!
The second most important factor affecting the flavour of your wine is the temperature in the vineyard. There can be big variations in temperature even within relatively small vineyards. This leads to big differences of flavour over short distances and may well lead to the “Terroir” differences that the French so love. It was thought that geology could have an influence on the temperature but it has been shown to be relatively unimportant. The aspect or slope of a hill is much more relevant.
There is an old-fashioned romance in saying that a wine reflects the soils that it was grown in, but, I’m afraid that appears to be less important than we used to think. Water and temperature are kings. Rocks are now scientifically consigned to playing a bit part.