Why do soil types matter to winos?
For those selling wine, mentioning the soil type can simply be a marketing technique to romance the product. Back labels on wine bottles are filled with this information. In other fields, sommeliers may flaunt their knowledge by mentioning the soil of a particular region.
What is often missing in the dialogue is the link about why soil is important. Why should the rest of us care?
And soil is such a complicated topic! In fact, the Paris Center of Agriculture offers a PhD on the topic (I’m not joking)! So we won’t cover everything in this post. But we can certainly cover the major themes.
So, here’s why soil matters.
Table of Contents
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In general, the #1 most important feature of any soil type is that they provide good drainage.
The number one most important quality about soils, is that vines want good drainage. The common adage is vines really don’t like to get their feet wet.
To this end, well-drained soils will help to increase grape quality. But it’s more than that! Well-drained soils will even aid the resilience of vines during droughts.
How?
By forcing the roots to grow further and deeper – like waay down into the soil.
Because deep, deep down, the roots will gain access to tiny amounts of water during dry spells. At the same time, the vines pick up more trace elements and nutrients along the way as there are more root tentacles piercing the subsoil.
As you can see, planting in soils with good drainage is pretty much a win, win situation.
Choosing the right soil type is far more important in Old World vineyards because they are not allowed to irrigate.
Allow me to start by defining two frequently used wine concepts, ‘Old World’ versus New World.
‘Old World’ vineyards refers to the wine regions of all of Europe. New World vineyards are those areas developed as a result of European colonization. Makes sense, right?
Generally, Old World producers are not allowed to irrigate their vines. This is a great plus for Mother Earth! As a result, European vineyards are planted where they naturally receive enough rainfall throughout the growing season.
Yet, not only is this a much more sustainable approach to agriculture, it has a fantastic effect on wine grape quality!
You see, roots are typically multi-branching; old, woody roots produce lateral roots that can further branch into smaller lateral roots.
In turn, these lateral roots produce many short, fine roots, thereby increasing the surface area of soil exploited for water uptake.
At the same time, water saturated soils do not have the airspace that allow vines to breathe. Returning to the beginning of the circle; vines don’t like to get their feet wet!
Why irrigation can possibly be bad for vines...
Therefore, those who rely on irrigation run the risk of misusing the technology.
For example, vines that are frequently irrigated well, don’t need to grow into the subsoil. Instead, they may only grow roots near the surface.
And vines whose roots only grow in the immediate topsoil die quickly when water is no longer available. Furthermore, these vines also tend to be less resilient towards a whole schwack-load of other pests and diseases.
In fact, many great Napa Valley viticulturalists I’ve spoken to will attest to this!
Ergo, skilled viticulturalists must know when and how to irrigate their grapevines for quality results. Furthermore, they must intimately understand the soil qualities where their vines are planted.
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Hillsides are great for providing good drainage
You may have also heard wine professional talk about hillside vineyards. Indeed, most of the vineyards in the Old World are planted on hills.
Why?
In France, monks of the middle ages recorded wine crop yields and quality over centuries. They were the first to figure out that grapes planted on hillsides made the best wine.
Today, we know why.
Did you know?
Through centuries of viticulture, literate monks kept detailed records of grape crops and resultant wines. They were the first to realize that hillside vineyards grew the best grapes for making high quality wine.
Why?
Hillsides drain rainfall exceptionally well; and vines don’t like to get their feet wet. Instead, the vine roots must stretch deep into the soil where they pick up trace elements and nutrients.
Yet, another reason why hillsides are great for wine grapes is because of the way the slopes face the sun.
Grapes grown in cool climates such as Champagne, just barely ripen each year. The south and south east aspects of the hillsides provide a direct route for the suns rays to ripen the grapes.
In other regions, hills may make the necessary adjustments in climate by providing altitude to cool things down as for this winery here.
We’ll be back to discuss why soils matter right after this quick announcement from our sponsors….
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To grow high quality grapes, the soil generally needs to be poor, infertile soils.
But the second most important thing about soils for vine grape growing, is generally soils should be infertile and lacking in the nutrients.
Why?
Planting in infertile soils is an easy way to restrict the vigour or productivity of the grapevine and therefore, produce less grapes.
Yes, I said that. The infertile soils produce less grapes and this is a good thing!
It’s counterintuitive, I know. With most agricultural crops, you want fertile soils because you want to produce as many tomatoes or peppers as possible.
However, grapevines are the opposite. Grapevines are essentially weeds so they will grow and grow and grow anywhere. In fact, in many places in Italy and Portugal, grapevines were planted beside trees and just left there. The trees provided a natural, low-maintenance anchor to climb and wrap around.
Because the truth is, if a vine produces too many grapes, the quality of the juice drops.
Instead, grapevines need to fight for their existence in order to produce high quality grapes for wine. This way, the plant focuses all of its energy and sugar production into the few grapes it has to attract birds to eat them.
Therefore, we plant grapevines in poor infertile soils to restrict their natural vigour and produce high quality grapes.
Conversely, grapes grown in the fertile plains such as the alluvial soils left over by riverbeds, produce higher yields of lower quality grapes. This makes absolutely fine inexpensive wines, but it doesn’t make premium wines meant for ageing.
Modern viticultural techniques allow us to control vigour without planting on hillsides
Yet, planting in poor, infertile soils is another broad generalization that more often applies to the vineyards of the Old World and even there it is still a simplified way of presenting a complex topic in one statement.
Many vineyards planted on fertile land can use other techniques for controlling yields and grape quality. Planting at super high densities is one way. Labour-intensive crop thinning is another common approach to minimizing yields for better grape quality. However, the second approach will require a skilled workforce and cost you a lot of money.
But the general idea is that where soils are poor, we are more likely to achieve quality grapes for making premium wines.
However, where soils are fertile – as in the valley plains near rivers -they tend to be higher yielding vines growing many grapes but producing grapes that make easy-drinking, simpler wines.
This isn’t to say that all flat, fertile vineyards make poor wine – noooooo. Viticulturalists have other ways of reducing yields – as the two common methods mentioned above.
It does mean that choosing to plant a vineyard in poor soils will reduce the amount of work you have to do later on to restrict yields.
Hence, soils are important: they affect the workload, the bottom line and the amount of money you can fetch for your wine.
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Subsoils and sometimes topsoils translate 'terroir'
Another reason why soils matter is because they have the ability to change the way the wine tastes. This is what we mean when we say soils have the ability to translate terroir. That means, soils affects the way a wine tastes.
Note that most of the time when producers are talking about soil types and terroir, we are talking about the subsoil.
However, there are moments when the spotlight shines on the topsoil as well. Most of the time this has to do with rocks absorbing heat from the sun during the day and later reflecting it back into the vines. In this case, the type of rock doesn’t really matter. (Well, I guess technically lighter coloured rocks reflect more solar radiation back to vines immediately, whereas darker rocks absorb more sun and release the warmth into the night. But we digress…)
How does this change the wine’s taste?
This extra, gradual ripening that happens after the sun goes down not only increases sugars for higher alcohol levels but more importantly it increases physiological ripening of the grapes, tannins and flavours.
The end result?
The resultant wine could exhibit riper fruits or floral notes, more fruit concentration, and/ or smoother tannin, for example – depending on the grape and the specific vineyard.
All this is precisely why WSET wine students and sommelier students are expected to know the soil types of famous wine regions.
To illustrate this point, we will now look at 4 famous wine regions and their soils, Rías Baixas in Spain, St. Émilion (Bordeaux) and Burgundy in France, and Chianti Classico in Italy.
Some soil types are warm; some are cool. Soil qualities like these combine with others for optimum grape growing.
If you want to plant a vineyard, you have to be careful to choose grape varieties that will work with the soil. You also need to balance that with the climate of the area.
4 concrete examples of how soils are matched with the climate and grapes for the 'perfect pairing'
To fully illustrate why soils are so important for wine grapes, let’s look at 4 classic wine regions.
First, we’ll look at the granite soils of Rías Baixas, Spain. We’ll discuss the rainy climate and see how granite enables optimal growth of the regions famous wines made from the white Albariño grape.
Next, we’ll hop over to the famous region of St. Émilion in Bordeaux and witness how the limestone escarpment makes grandiose Merlot bottlings. Next up on our journey, we’ll make a brief detour to Burgundy, the very birthplace of ‘terroir’. We’ll listen to Edouard Labruyère of Maison Jacques Prieur share how his Pinot Noir wines taste different even when the grapes are grown within the same village.
Finally, we’ll travel to Tuscany and witness the great Sangiovese-based wines of Chianti Classico. Here knowing the soil where the grapes are grown will help you make better buying decisions.
The soil of Rías Baixas, Spain
The white grape Albariño thrives in Rías Baixas in the northwest of Spain because of the granite topsoil and subsoil.
There are 3 reasons for this.
The first, relates to reason #1 above – granite or rocks in general, provide good drainage. See the box below.
Why does Albariño grow so well in Spain?
Rías Baixas in Spain has a cool and sunny mediterranean climate as the region lays right on the edges of the ocean. So, it also rains a lot.
On average, it rains 1600 mm per year in Rías Baixas. Some estates even experience 2000 mm per year. Compare that to Alsace where it rains only 500 mm per year.
(Overall, grapevines only need between 300-600 mm of rainfall per year).
The granite soils of Rías Baixas make sure that the vine’s feet aren’t always soaked. To boot, these vineyards are also along the hillsides which helps rid the soils of all that excess rain.
The second reason why granite soils work so well is to due to reason #2. Granite is a poor, infertile soil that helps to keep the yields down.
However, thirdly, granite is a cool soil. It warms very slowly at the beginning of each day and the season thereby slowing down the growth enabling complex flavours to develop. Perhaps paradoxically, granite simultaneously reflects added heat from the sun back on the vines at night when its cool.
Furthermore, cool soils (and temperatures) are able to maintain high levels of acidity in the grapes. And wines that gain high acidity naturally through their climate are highly valued by wine professionals (instead of say, by adding tartaric acid in powder form).
For those new to the world of wine, acidity is what gives wine that mouthwatering quality. It not only enhances the wine’s compatibility with various foods but also contributes to its ability to age gracefully.
SommWine Tip
- If you like ‘richer’ wines – choose clay soils!
- I recently fell in love with this Scariazzo Fiano. It’s BEAUTIFUL! The richness in this wine can be, in part, attributed to the clay soils the grapes are grown in.
- Because clay soils and their derivatives (limestone and especially calcareous clay) produce fuller-bodied, richer wines
- Why? Clay soils provide the potassium that vines need to form sugars and starches
- But that’s not all! Clay also provides phosphorus to encourage bud initiation which is really good for say, minimal-intervention winemaking. Finally, because clay retains water, it maintains cool, consistent temperatures below the vine. Cheers to that!
St Émilion, Bordeaux, France is famous for its cool, limestone soils
Limestone is a type of clay formed from millions of tiny ancient shells of sea creatures on the seabed and is also a cool soil. Limestone is truly unique in that it retains moisture in dry weather, but also offers good drainage in cool weather. In short, limestone produces high quality grapes especially in cool climates.
As a perfect example, the best estates in St. Émilion in Bordeaux have cool, limestone and clay soils that maintain acidity in Merlot grapes. In fact, the best estates of St. Émilion are sitting on a famed ‘limestone escarpment’. Think of the most illustrious names of the region; Châteaus Pavie, Ausone, Figeac, Canon, La Gaffelière all benefit from their vinyeard location on limestone soils.
Allow me to extrapolate.
Most of the time, Merlot isn’t considered a ‘serious’ wine. Their wines are often plush with dark plum fruits and chocolate. They are smooth and velvety, but they cannot age in your cellar for long and often miss the je ne sais quois factor.
But one place where Merlot shines is in St. Émilion! Here the soils are cool enough to get the fruit ripeness in the grapes AND retain high acidity for long ageability.
On the flip side of the coin, warm soils are also important to certain regions because they can help ripen grapes in marginal climates.
For example, the slate rocks of the Mosel Valley help to reflect heat back onto the vines to increase ripening in the marginal climate of northern Germany.
Sandy soils are known to be warm soils.
For the record, soil is just as important in New World vineyards as it is in the Old World.
On this thread, allow me the time to tout some absolutely killer BC Merlot’s being made in the Similkameen Valley such as Clos de Soleil’s Celestiale and Hugging Tree Winery’s Moonchild Merlot. These grapes benefit from their gravelly, sandy loam subsoils – the same subsoils of Napa Valley.
But it's not just the quality of the grapes and wine structure that are affected by soil types. Changes in the soil affect the flavour of the wine too.
If you speak with the producers in Burgundy, France, they will ALWAYS talk about the soil and the flavour of the wine in the same sentence.
In fact, Burgundy is THE birthplace of terroir.
It’s so important, entire books are dedicated to mapping the tiny differences in soil throughout Burgundy.
Here is a graph of the changes in soil type on the Côte (hillside) in Burgundy.
More to this point, is this video of Edouard Labruyère, the owner at Maison Jacques Prieur in Burgundy, France. Listen to how he explains the flavour difference between his Chardonnay-based wines – all from vineyards within the same village in Beaune, Burgundy. The changes all have to do with the soils the grapes were grown in.
In warmer climates, sandy soils generally produce wines that are softer (lower in tannin), paler in colour, and higher in elegant aromatics.
Conversely, wines whose grapes are grown in clay-limestone soils, are more tannic, deeper in colour and have bolder flavours.
Therefore, the same grape variety grown in warm sandy soils will produce a different wine if grown in clay-based soils like limestone.
Chianti wines made with Sangiovese illustrate how soil affects flavour
Galestro, a schistous, marl-like sand with a touch of clay produces wines that are more robustly fruit-driven. These soils are generally found in the higher elevations of Chianti.
Alternatively, albarese, a white clay that’s generally found in the lower elevations of Chianti, produce wines that are more savoury and mineral.
Let’s bring back the example of the Merlot-based wines grown on the limestone-clay soils of St Émilion in Bordeaux, France. Now, you can perhaps understand why the wines here are structured (tannic), deeply coloured and have intense concentration of flavours.
Summary...
For most people drinking wines, soil types shouldn’t really matter. But, if you’re truly passionate about wines from a particular region, delving into the soil’s secrets and its impact on flavor and quality can be a rewarding journey.
While wine professionals often wax poetic about the soils in which their grapes grow, they might overlook the vital question of why soil truly matters – unless you ask!
You see, most soils excel at ensuring proper drainage, preventing excess rainfall from dampening the vines’ spirits. This, in turn, fortifies the vines, making them more tenacious during droughts. These resilient vines extend their roots deep into the earth in search of water.
In another example, cool soils establish a consistent temperature underground. Thus cool soils take care of vine’s roots by providing them with a sense of stability and security. Cool soils further help grapes maintain their mouthwatering acidity, a crucial element for ageing wines. While conversely, warm soils can help ripen grapes in marginal climates. And most importantly, distinct soil types can wield their magic to transform the flavours in the wine – this is why wine aficionados love to toss around the concept of ‘terroir.’
In the grand scheme of things, knowing whether those grapes grew in sandy or clay soils can guide us in selecting the style of wine that aligns perfectly with our taste buds. So, next time you’re sipping your favourite vino, you’ll have a little extra knowledge to savour. Cheers! 🍷
2 Comments
Barrel role. The soil article is great. Do the same for barrels! Thank you!
Thanks for your comment, Sam! I addressed at least some of the role wine barrels have on wine flavour in this post here: https://www.sommwine.com/4-exciting-bc-trends/ . Check it out and let me know in the comments if there are any other specifics you’d like me to cover. I’m more than happy to oblige!
Joanne