Introduction to Soil Types and Wine

What are the best soil types for wine grapes?

One of the most frequently mentioned traits of a great wine is the soil. The conversation usually sounds something like this:

“This estate is certainly well-located, resting on well-draining, gravelly soils with some veins of clay running through them.” –Château Charmail, Haut-Médoc, Bordeaux

So, now that you’ve read the statement above, you might be wondering: “What the heck does that mean?”

Introduction to Soil Types and Wine

Here are two very common questions when it comes to soil and wine:

• Question: Do great wines only grow on certain soils?

  Answer: Yes, but it’s complicated. There are several factors, including climate, elevation, type of grape, and style of wine, that affect which soil is best.
   

• Question: Do earthy flavors in wine come from the soil?

  Answer: No. Believe it or not, this assumption has never been proven!

Fortunately, we can understand wine a little better by paying attention to how wines behave in four primary soil types:

1. Sandy Soils
2. Clay Based Soils
3. Silt Soils
4. Loam Soils

1. Sandy Soils

Elegant wines with high aromatics, pale color, and low tannin.

Sandy soils are well-draining and retain heat. In warm climate regions, sandy soils make wines that are ‘softer’ with less color, lighter acidity, and tannin. If you’ve ever had a pale wine from Swartland, South Africa, this is part of the reason why.

In cooler climate regions, sandy soils benefit vineyards by retaining heat and draining well, producing highly aromatic wines. A side benefit of sandy soils is their resistance to pests, which could encourage more organic production in the wine region.

Famous Wines From Sandy Soils

Cannubi is a top cru of Barolo with sandy clay soils. The wines from Cannubi are noteworthy for their intense aromatics, light tannin, and very pale color. You’ll also find plenty of sandy soils in the Northern Médoc (close to the sea) and Graves in Bordeaux. These regions produce lighter and more aromatic Cabernet Sauvignon. In Lodi, there are several plots of 1890s Zinfandel, including Leland Noma’s Cemetery Vineyard that survived grape phylloxera because of the sandy soil.

2. Clay Soils

Muscular wines with high extract and color.

Clay soils tend to stay cooler and retain water. There are several types of clay soils, including callous clay, a lime-rich clay that is said to be even cooler. These soils are famous for producing some of the boldest red and white wines in the world.

Famous Wines From Clay Soils

The highest-quality Tempranillo vineyards grow on limestone-rich clay soils in Rioja and Ribera del Duero, Spain. In Burgundy, Vosne-Romanée is notable for producing the world’s most famous Pinot Noir on clay-limestone soil called Marl. In Chianti, the Albarese soil is a clay-limestone soil that makes bold Sangiovese wines. Finally, several hillside vineyards in Napa and the great Shiraz vineyards of Barossa are mostly on clay-loam soils.

3. Silt Soils

Smooth and round wines with slightly less acidity.

Silt soils retain water and heat. In cooler climate regions with sun, the ideal silt soil sites tend to mix with a portion of limestone. Silt soils are very fine-grained, which makes growing roots very difficult.

Famous Wines From Silt Soils

The Loess (wind-blown silt) soils in eastern Washington are the top layer of soil that covers the sandy-loam ancient flood soils below. Washington wines are highly aromatic, slightly lighter in color, and smooth in tannin. In Oregon, one of the favorite soil types for Pinot Noir is Willakenzie, a silt-clay soil.

4. Loam Soils

Unless it’s blended, loam soil is typically too fertile.

Loam is nearly an equal mix of silt, clay, and sand and an organic matter called humus. Loam is very fertile and typically causes vineyards to be over-vigorous. Because of the vigor, most loam soils produce wines that have very little flavor and color. Despite this fact, loam soils offer great potential with wines made from vineyards that have rigorous pruning regimes.

Famous Wines From Loamy Soils

Much of the valley parts of Sonoma Valley and Napa Valley is made up of a sandy-loam. The sand keeps the soil poor enough to produce high-quality wine grapes.

What about Gravel, Schist, Slate and Volcanic Soils?

When it comes to gravel, slate, and schist, rocks can change the temperature of a soil (by retaining heat or reflecting sun), and they also affect drainage. In the case of Bordeaux (which we mentioned above), the gravel in the clay soil increases drainage. The blue slate rocks of the Mosel Valley in Germany retain heat from the sun, which is great for the cool climate region. Decomposed volcanic soils are known to retain water, which can be good in dry regions such as Lanzarote in Spain.