Book Review: Vineyards, Rocks, & Soils
The relationship between soil and wine is one that is widely discussed, but in often nebulous terms. Words such as minerality, chalky, and talcy are used without any specific definition, while implying an inherent influence of a particular type of soil on the taste of a wine even though minerals, chalk, and talc don’t smell or taste of anything.
It’s a relationship I’ve always had issue with. To argue - or even imply - that a vine takes up flavours from the soil which are then imparted into the resulting wine is too literal and simplistic. When we talk about a wine tasting of strawberries or cinnamon, we are doing so metaphorically, but many tasters and writers insist on a much less figurative use of soil-related descriptors.
At the same time, certain grape varieties perform much better on certain soil types; likewise, a grape variety can produce a different style of wine according to the soil on which it is planted. As a colleague of mine recently observed: “Chablis is Chardonnay, but Chardonnay is not Chablis.”
Wine geeks such as me engage in these discussions on a regular basis, without really knowing what we’re talking about, so it was with great interest that I picked up a recently published book on this subject by Alex Maltman, a geologist who has disputed that soil has a direct influence on the taste profile of a wine.
It’s called Vineyards, Rocks, & Soils: The Wine Lover’s Guide to Geology, and it is a thorough, in-depth, but fairly approachable introduction to geology, with many specific examples of wine regions across the world.
Maltman is clear that there is no direct relationship between soil and aromas in a wine. Minerals are flavourless; there’s no way that roots pick up aromas from the soil and transfer them to the grape. Moreover, most vines are planted to American rootstock - if the vines’ roots were taking aromas from the soil, they would also be influenced by the roots themselves. That, of course, was the initial reason the French were reluctant to graft American rootstock as a deterrent against phylloxera - but that concern ceased to be an issue 150 years ago.
But for all that, soil is clearly important because that’s what vines grow in. Soil is a living material which provides water and nutrients for the vine to live. There are many different soil types which affect how the vine grows, and this where Maltman’s argument becomes extremely interesting and convincing.
This book isn’t just about soil, it’s about rocks and minerals and how they’ve been formed over millions of years. That formation, whether it’s been through volcanoes, pressure, or erosion, has changed the soils and the way they are constituted as well as the slope, aspect, and contours of a vineyard. This is the true expression of terroir: how millions of years of movement have created the perfect (or imperfect) conditions for grape growing.
These growing conditions created by geological movements directly influence the vine and the resulting wine. The depth, strength, and porosity of the soil create a balance between water retention and drainage. The position and aspect of the vineyard changes the effect of the sun on both the soils and the vines. Sunlight is, of course, all-important for photosynthesis, but different soils will react to sunlight in various ways: a pale-coloured soil reflects sunlight on to the vine, while a dark-coloured soil retains warmth from the sunlight, warmth which will be transferred down to the vine’s roots. This is why it’s possible to make high-quality Pinot Noir in Ahr, which is Germany’s most northerly wine region - it has dark-coloured slate, basalt, and greywacke soils.
But it’s not just the position of a vineyard that changes growing conditions; within a vineyard, vines can grow at different rates. This is called the microclimate and from vine to vine air and leaf temperature, sunlight intensity, humidity, and air flow can all vary.
The reason the French word terroir (which is quite a recent creation) is impossible to translate is because it doesn’t just refer to one single concept. It isn’t just soil, it’s also water (in the soil or nearby bodies of water), air, aspect, elevation, sunshine, wind, bacteria, rootstock, warmth, and, of course, we humans.
In this book, Maltman makes clear how complex the formation of the earth around and beneath us is and how the relationship between soil and wine is not a straightforward one that has literal implications on the taste of wine; instead, the influence is indirect, particular to site, and fascinatingly diverse.