Soil is the part of a wine's terroir that lies below ground. It does not give wine its flavour directly, but it shapes how the vine grows: how much water the roots can reach, how many nutrients are available and how quickly the ground warms up. That shows in how the grapes ripen and in the wine's acidity, structure and aroma.
How does soil affect wine?
Water and drainage
The most important thing soil does is regulate water. Fast-draining soils such as gravel, sand and slate force the roots to dig deep. The vine gets a steady but limited supply and produces smaller, more concentrated grapes. Clay holds on to water, which helps in dry years but can lead to too much growth when it rains a lot. Limestone sits in between: it lets the excess drain away but keeps a reserve the vine can draw on through the summer.
Warmth
The colour of the soil and its stones affect temperature. Dark slate and stony ground store the sun's heat during the day and release it in the evening, which helps grapes ripen in cool sites such as the Mosel. Pale limestone stays cooler, and damp clay warms up slowly in spring.
Nutrients
Poor soil is usually an advantage. When the vine does not get too many nutrients, it puts less energy into leaves and shoots and more into the grapes. Fertile soil gives large yields, but the wines are often thinner.
The most common soil types
- Limestone: holds water well yet still drains, and often produces wines with high acidity and tension. Chalk is a soft, porous form of limestone that defines Champagne. In Burgundy, Chardonnay and Pinot Noir grow on limestone and marl, and Chablis sits on lime-rich clay full of fossilised oyster shells.
- Clay: holds a lot of water and stays cool, and often produces fuller, more powerful wines. Merlot on the Right Bank of Bordeaux, in Pomerol and Saint-Émilion, is the classic example.
- Gravel: drains quickly and warms up, which suits late-ripening grapes such as Cabernet Sauvignon on Bordeaux's Left Bank.
- Sand: light and warm, and often produces aromatic wines with softer tannins. Phylloxera struggles in sand, so some old vines on their own roots survive there.
- Slate: stores heat and drains well. Known from Mosel Riesling and from Garnacha and Cariñena in Priorat.
- Granite: poor and fast-draining, and often produces fresh, lively wines. Gamay in the cru villages of Beaujolais grows mainly on granite, in some villages also on slate, and Riesling on some grand cru sites in Alsace grows on granite.
- Volcanic soil: porous and rich in minerals. Known from Etna on Sicily, with the grapes Nerello Mascalese and Carricante, and from Santorini and the Canary Islands. The wines are often described as taut and salty.
Soil and grape belong together
No soil is best in itself. What matters is how soil, grape and climate fit together. Chardonnay on limestone in Burgundy, Riesling on slate in the Mosel and Gamay on granite in Beaujolais are pairings growers have refined over generations. The same grape on a different soil makes a different wine, which is why two wines from the same village can taste different.
What does mineral mean?
Mineral is one of the most common words when soil comes up, but it describes an impression, not the taste of stone. The vine takes up minerals as nutrients, but in amounts far too small to taste in the wine. What people call mineral is more often linked to high acidity, restrained fruit and sometimes a little reduction from winemaking. The word is useful for describing a style, but it does not reliably tell you which soil a wine comes from.
How to find the soil for a wine
On the wine pages at Free Grape Society, many winemakers list the soil under Soils, in the vinification section. There you can compare, for example, a Champagne from chalk with a Gamay from slate or a wine from the volcanic slopes of Etna. You can read more about how soil works together with climate, site and people on the page about terroir.
