What is terroir and how does it affect wine?
Terroir ("tear-wah") is a French word and that's difficult to understand, but it loosely translates to a land's potential to produce agriculture. Interestingly enough, where and how the grapes grow affects how wine tastes.
To better understand terroir, let's break it into three categories:
- A wine region's climate
- The soil and terrain conditions
- Common winemaking practices
Together, these three characteristics help explain why certain wines from specific places have this "je ne sais quoi" – an undefinable yet unmistakable taste.
Bordeaux Terroir Overview
Most of Bordeaux is pretty wet as it sits right next to the Atlantic Ocean. The Landes Forest protects it a bit from the worst weather, but it still rains throughout the year, and in some years it can rain during harvest too.
Bordeaux has a maritime warm climate. The average growing season temperature of 64 ºF (18 ºC) and the region receives 31 inches (800mm) of rain during the year. These are challenging conditions to ripen a sun-loving grape like Cabernet Sauvignon.
Most growers, faced with a climate like this, would look for a south-facing slope to plant their grapes on (this increases heat, sunlight, and drainage). But the highest point in all of Bordeaux is only 45 m above sea level–it's flat! So, how did the Bordelais solve this problem?
They pay close attention to the dirt.
Soil type dictates what grapes are grown
Bordeaux is more or less cut in half by the Gironde Estuary (where the Dordogne and Garonne rivers meet). When looking at a map of Bordeaux, the left side is called the “Left Bank” and the right is called the “Right Bank”. Why is this so important?
Well, one of the biggest differences between the Left and Right banks is what’s in the soil. The Left Bank has more gravel and the Right Bank has more clay and limestone.
Gravel soils are warm and Cabernet Sauvignon likes heat
Cabernet Sauvignon has bold black fruit flavours, high levels of tannin and acid, and herbaceous notes. It needs gravel soils to ripen successfully, and that’s why we see more Cabernet Sauvignon in the Left Bank than anywhere else in Bordeaux.
How does that work? Bordeaux sits at almost 45 degrees north of the equator with 2050 hours of sunshine - this can be thought of as the dividing line between warm and cooler climates.
Cabernet Sauvignon needs more heat than other varieties to fully ripen (needs more heat than Merlot). This means Cabernet Sauvignon needs the warmest sites in Bordeaux to be happy.
Quartz pebbles on the Boyd-Cantenac estate in Margaux.
And you guessed it, gravelly soils are warmer than clay soils.
Think of little tiny rocks heating up during the day, holding onto that heat and giving it back to the grapes at night. Also, gravelly soils drain easily, which is also important in the rainy, maritime climate of Bordeaux. This combo means that in most years Cabernet Sauvignon grown on gravelly soils will have no problem ripening.
This is why the best areas for Cabernet Sauvignon are on the Left Bank. Places like Pauillac and Margaux have big mounds of gravel and therefore are able to produce amazingly tannic, age-worthy Cabernet Sauvignon based wines, with aromas of tobacco, leather, and smoke.
Sémillon, a white grape, also needs a bit of extra heat to ripen, and though there’s not much of it planted in Bordeaux, the best expressions of it come from gravelly, well drained soils too.
Clay soils are cooler and Merlot needs to chill a bit
Merlot, on the other hand, with it’s smooth tannins, full body, and mix of red and black fruit flavours, isn’t nearly as fussy when it comes to heat - it doesn’t need as much warmth to ripen, and so it can be planted on clay soils and be just fine.
This is why we see it planted all over Bordeaux (gravel soils are relatively rare). Clay soils take a lot longer to warm up and also hold a lot more water, meaning overall it’s a cooler soil than gravel. As Merlot is an earlier ripening grape than Cabernet Sauvignon, these cooler soils are better suited for it.
Two soil pits show the blue clay vein and an iron-rich deposit on Château Gazin in Pomerol.
Merlot finds its best expression on the Right Bank in places like Pomerol and Saint-Émilion. In Pomerol there’s a lot of clay, gravel, and iron-rich deposits which contribute power and finesse to the wines.
In Saint-Émilion, a mixture of clay, limestone, and gravel allows Merlot and Cabernet Franc to have immense structure and power. These wines, like the finest wines from the Médoc, age for decades, revealing aromas of chocolate, meat, and dried fruits.
Sauvignon Blanc also doesn’t need much heat to ripen, and when it is planted throughout Bordeaux we see it happily ripening on clay and limestone, but also sandy soils too.
Tasting each barrel helps the winemaker in blending. Winemaker at Vieux Château Certan.
Difficult growing conditions means everybody blends
Since Bordeaux has such a marginal climate, especially for red grapes, winemakers make blends.
In cooler years, Cabernet Sauvignon struggles to ripen. This creates a tannic, acidic, and somewhat harsh style of wine and you need something to soften it. Merlot does exactly that. Merlot has smoother, softer tannins, and a fuller body than Cabernet Sauvignon.
Therefore, Left Bank wines are mostly Cabernet Sauvignon but with some Merlot blended in - the percentage of each will vary depending on the condition of each vintage.
On the Right Bank, you will still see blending in the Merlot dominant wines, mainly with Cabernet Franc - this grape brings tannin, acid, black fruit and floral aromas to a Merlot blend.
Misty Mornings and Sunny Afternoons - Sweet, Sweet Noble Rot
About 25 miles (40 km) south of the city of Bordeaux the Ciron and Garonne rivers meet. These slow moving rivers create a lot of humidity and mist.
It creates noble rot caused by a fungus called Botrytis cinerea on Sémillon and Sauvignon Blanc grapes.
Botrytis cinerea pokes microscopic holes into the skin of the grape and this allows for a slow dehydration and concentration of what’s in the berry: sugar, acid, and flavor.
Noble rot also adds its own flavors of marmalade and orange peel.
A view of these ideal conditions at Château Suduiraut at harvest that create noble rot.
The resulting wine is lusciously sweet and super concentrated with flavors of citrus, honey, marmalade and more from both the grapes and Botrytis cinerea. While you can drink these wines right away, many believe this wine ages well for decades.
Areas with these unique climate condition skirt along the Garonne river. Thus, all of the appellations in this area are known to produce sweet, noble rot wines.