“Wine starts in the dirt, and the dirt starts with geology,” says David Howell, a former research geologist with the U.S. Geological Survey. How often do you think about dirt when you drink wine? Probably never, but it’s important. As much as you’d probably prefer not to think about literal dirt while consuming something delicious, when it comes to wine, so much of what you’re tasting comes from dirt.
A world-class wine region needs well-formed soil and a complementary climate to thrive. There are four primary soil types: sandy, clay based, silt and loam. You can grow grapes in any of these soils, but the resulting harvest and wines will differ greatly.
Sandy soil is well-drained, retains heat and lends itself to a very aromatic, pale wine. You aren’t going to get a super acidic or heavy wine from a sandy soil. Considering how well light, white wines sell in warmer, more beach-friendly months, it seems appropriate that warmer, more beachy environments produce lighter, paler wines.
Just as clay seems to directly oppose sand, so to do the wines that come from clay based soils. Clay tends to stay cooler and retain water, the result are bolder wines. White or red, clay soils produce some of the boldest wines in the world. The reds that grow in clay soils are vivid and high in color.
If clay and sand produce opposite wines, silt falls in the middle. Grapes grown in silt soils produce smooth, balanced wines with less heft and acidity than clay, but more punch than sand. Silt retains water and heat and can be difficult to grow grapes in due to how fine it is, but if you get growth, you’re gonna get something good.
Finally, there’s loam soil. Whereas silt can be challenging to grow in, loam is easy to grow in. In fact, loam is too easy to grow in. Loam’s excessive fertility can cause vineyards to be overly vigorous and, as a result, loam grown grapes often produce wines that are low in flavor and color. That’s not to say loam should be avoided, it’s fertility is a valuable asset, but one that should be used sparingly and/or strategically. Loam in combination with another soil type can produce very interesting and dynamic wines.
Wine is the sum of so many parts. The process is nuanced and seemingly magical at times. There are so many factors that go into shaping a wine’s flavor, and it all starts at the start with where you plant the seed – not the length of fermentation or whether it was aged in oak or a stainless steel barrel. It started with the soil. So, the next time you enjoy a glass of wine, think about dirt. We promise it won’t be weird.