Terroir – Why Does It Matter?

Wine professionals and connoisseurs love to throw around the term “terroir” (“tehr-WAH” or “tehr-WAHR”). Few people have a clear idea of what this word means. For many, there is a vague notion that terroir refers to climate and wine quality, but the exact variables involved are mysterious. In this post, we’ll examine the meaning of the term “terroir” to better understand its relevance to our lives as wine lovers.

Old vs New World

The concept of terroir is native to Europe – France in particular. Over the centuries, winegrowers in places like Burgundy observed that wines from certain vineyards seemed to have unique characteristics that could not be attributed to winemaking practices such as fermentation and aging. In other words, the grapes themselves seemed to express unique flavors related to their location – even before they were harvested. Winemakers noticed differences between a wine from one vineyard versus another, even though the farming and vinification techniques were the same for both wines. Various theories were advanced to account for these differences, including soil type, drainage, temperature, aspect, sunlight, and access to water. Observing these differences in vineyard sites, and the wines they produced, leads to a complex system of individually recognized sites with distinctive characteristics. This way of understanding grape growing and winemaking underpins the French legal designations for wine. Terroir can be defined as “the totality of geographical, biological, and climatological factors that make a particular vineyard site unique.”

In the New World, by contrast, wineries have traditionally been more concerned with the type of grapes being planted and the winemaking process than the subtleties of terroir. Some will even go so far as to deny the validity of the terroir concept, while others have adopted the ideas of terroir-centric winemaking, thereby implementing a French approach to viticulture. The idea of terroir continues to be debated and studied, with new ideas and discoveries being advanced around the world.


For centuries, winemakers have claimed that particular soil types result in particular flavors in wine. For example, the flinty limestone soils in Pouilly-Fumé are said to impart a flinty flavor to the wine. Research is ongoing as to the cause of these perceived relationships. Clearly, grapes grown in different places taste different, but given that vines filter the nutrients they need from soil, rather than simply absorbing its contents, the exact effect of soil on wine flavor is yet to be scientifically determined.

Ripening: Sugar, Acidity, Temperature, and Sunlight

As grapes ripen, their acidity is reduced and their sugar is increased. Less ripe grapes are tart and dry; riper grapes are sweet and less sour. Two factors that affect the ripeness of grapes, and therefore their flavor, are temperature and sunlight. Grapes cannot ripen well if the air is too cold or the sky is too cloudy. Top wine regions tend to be ones with warm (not hot), sunny summers. Temperature and sunlight are affected by multiple factors, including relief and latitude.


This aspect of terroir relates to the shape of the land itself: its hills, elevation and the direction of slopes, relative to the sun. A higher elevation can result in lower temperatures, but also more intense sunlight. Steeper slopes can provide drainage, which is very important, as damp soil is bad for wine quality. Steep slopes also increase the intensity of sunlight, particularly in higher latitudes, by angling the vineyard towards the sun. The direction of slopes is also very important. Most vineyards in the northern hemisphere are best on south-facing slopes, because it increases sunlight exposure. Again, sunlight is important, as it helps promote ripeness in the grapes. Note that sweet grapes do not necessarily result in sweet wines – sugar is converted into alcohol during fermentation, so sweet grapes can produce dry wines with high alcohol and full body.

An example of the importance of relief in terroir is the Mosel Valley in Germany. Most of the land around Mosel is quite cold, but there are steep, south-facing slopes at the edge of the river that not only present a more direct angle for sunlight on the vines, but also catch the light reflecting off the river, which warms the plants. This special hillside terroir makes viticulture possible in a climate that would otherwise be too cool for grape growing.


This facet of terroir relates to the distance from the vineyard to the equator. The further north the vineyard site, the cooler the climate is likely to be. On the other hand, high latitudes also have longer summer days. Washington State, for example, is north of California but has longer days. The eastern portion of the state has a desert climate, which offsets the cooling effect of its latitude, so that winegrowers can ripen their grapes to perfection in the extended hours of bright sun.

Water and Soil Fertility

Grapevines produce their best fruit when under stress. When they have all the water and nutrients they need, they concentrate their energy on photosynthesis and the growth of new leaves, rather than grapes. The grapes that are produced by such happy vines are usually watery and bland. On the other hand, when a vine is stressed by poor soil and dry conditions, it begins to prioritize the production of concentrated, flavorful fruit over new foliage. This is why so many wineries will brag about their dry-farmed vineyards and poor rocky soils. As the old saying goes, “vines don’t like to have wet feet.” Some vineyards in Spain are famous for being unirrigated in sandy soil. These vineyards generally produce extremely flavorful wines.

Temperature Variation

Another factor affecting grape quality is temperature variation. Disparate temperatures between day and night allow grapes to develop complex flavors over the course of the summer. Warm days bring ripeness, while cool nights preserve freshness. One of the places with unique terroir in regard to temperature variation is in California, just north of San Francisco. Napa and Sonoma counties are close enough to the bay that they are bathed in fog in the mornings, which cools the vineyards. In the afternoon, the fog dissipates, allowing the vines to warm; at night, the clear skies lead to cool nights. This temperature variation is one of the reasons that Napa and Sonoma have such special terroir.


One of the aspects of terroir that is least understood is the microbiology of individual vineyard sites. Scientists are beginning to understand the enormous diversity in the bacteria and fungi that live in the air and soils. These microscopic lifeforms may have more of an impact of the individuality of particular vineyard sites than we know. Hopefully, we will see more studies in future years to shed light on this less-explored aspect of terroir.