Terroir debate: Does schist affect wine flavour?

Andrew Jefford attends a ‘terroir tasting’ – and addresses one of the key wine questions of our time...

Let’s start … with lovely mud. It’s mixture of loam, silt and clay particles with water. Ancient or consolidated mud becomes a sedimentary rock: mudstone (if it breaks into chunks) or shale (if it breaks into slices)

If those sedimentary rocks are buried and subjected to pressure and heat, they become metamorphic rocks; their constituent minerals are reorganised. Clay minerals in particular are susceptible to change. Shale, if buried and subjected to oven-like temperatures over millions of years, gradually becomes slate. It might, at that point, find itself back up at the earth’s surface – or it might continue to descend further, into hotter zones, for more millions of years. If so, it will become schist. Pile on even more depth, pressure and heat and you’ll end up with gneiss.

All of these rock types have a multitude of variants and sometimes intermediate stages (like phyllite between slate and schist), and anyone who has read widely in wine literature will know that the names shale, slate and schist have fluid boundaries and overlapping applications. When does day become night? Where does one octave end and another begin? In continuous processes, all divisions are arbitrary.

Shale, slate and schist also happen to be key rock types in certain fine European vineyard areas. Many of Germany’s greatest Rieslings grow in the bare slate rubble of the Mosel and Rhine valleys; while most vines in Portugal’s Douro valley and Spain’s Priorat gnarl up out of a stony chaos of schist (though the Spanish term llicorella is generally translated as ‘slate’, underlining the haziness of nomenclature to which I have just alluded).

Since the topographies and/or climate regimes of these areas militate against thick soil layers and lush swards, both wine lovers and growers are familiar with the striking appearance and physical quiddity of the broken rocks themselves, and tend to marvel at the heroic endurance of often unirrigated vines planted in them many decades ago. When we sip wines from these places and find unfruity flavours which intrigue us, or note textural amplitude in the reds, we may assign such flavours and textures to ‘minerality’ — or even ‘slatiness’ or ‘schistiness’.

Are we correct? If so, by what means or mechanism might rock type influence wine flavour and texture — the outcome, after all, of the processing of a fruit crop? Or are we, distracted by vineyard appearance, signing up for a religion of the rocks? This is one of the key wine questions of our time.

A couple of weeks ago, I attended a tasting organised by ‘Terroirs de Schiste’ – a grouping of mainly French wine producers (though there are members in Priorat and the Valais too) working with distinctive schist vineyards. Faugères growers are prominent (the group’s President is Bernard Vidal of Ch la Liquière) and there are other members from Collioure, Maury, Fitou, St Chinian, Cap Corse, Savennières and Alsace. After an introduction to the subject of schist from geology Professor Jean-Claude Bousquet (who, by the way, has written an excellent introduction to the geology of Languedoc vineyards called Terroirs Viticoles: Paysage et géologie en Languedoc, available here), we then tasted ten white wines and ten red, all grown in schist zones, in an attempt to find some sort of common sensorial thread between them.

The group verdict, based on the discussions among the attending sommeliers and growers afterwards, was that there was indeed a common thread to the white wines, but that various levels of fruit maturity and contrasting winemaking processes made it difficult to generalise about the reds. The whites were said (by various interlocutors) to have “freshness … attractive bitterness … elegance … aniseed or fennel notes … salty edges”; some tasters felt that their varietal notes were subdued and that there was a “mineral-bitter” spectrum in place of those varietal notes.

The growers pointed out that schist soils, usually acid in themselves, tend to give high pH wines (and that conversely high pH limestone soils tended to give lower pH wines) — but that, despite this, schist soils seem to bring freshness. They also pointed out that vines struggle and die more quickly on schist soils than on limestone soils, hence that growers on schist need to be very attentive to their plants. The Languedoc AOC’s technical director, Jean-Philippe Granier, said that 30 years of experience suggested to him that there was a fundamental difference between wines made from vines grown on limestone and schist, and felt sure that most consumers would be able to recognise this.

I’m … not so sure. In this tasting, and in the few similar tastings I have done of this sort, the principal sensorial differences between the wines seem to be overwhelmingly derived from climate zone, variety and winemaking strategy. The reds we looked at, for example, began with an Anjou Gamay and included young Maury Sec and Coteaux du Cap Corse before finishing with a nine-year-old Swiss Syrah. This was, in other words, a comparison of vastly dissimilar wines, so it was no surprise that the reds showed little commonality.

The best place, in fact, to organise such a comparison would be St Chinian, an appellation with both limestone- and schist-derived soils in close proximity. Identical blends made identically in the same cellar from schist and limestone vineyards lying at the same altitude and with the same exposure in the same vintage might provide a valid comparison and enable tentative conclusions about the effects of each soil type to be drawn.

It was true that there were more similarities among the white wines, but that was because all save the last three were made in France’s deep south, from an identical vintage (2015) and from a similar pool of (generally undemonstrative) grape varieties, including Grenache Blanc, Clairette and Vermentino. The moment we moved away from that cohort to wines from Savennières, Alsace and the Valais, the thread was lost. I doubt, therefore, that a tasting of this sort could ever reveal, time after time, a palpable sensorial key for a heterogenous group of wines which happen to share no more than soil type in common.

I’m, though, glad that we’re beginning to test these notions, and I remain devoted to the idea that the physical and chemical environment for the rooted vine (of which soil type and mineral composition is just one element) must be of some consequence. As I tasted these 20 wines, it struck me that – at this macro level — soil type is perhaps best seen as an enabler of possibilities or a provider of qualitative horizons rather than something which brings any kind of clear sensorial stamp. In the sensual profile of most wines, it is an undertone compared to the overtones provided by climate, variety and winemaking strategy.

The importance of soils increases within single climatic zones of proven quality attainment where practitioners are generally using a single variety or standard blend, and share winemaking techniques; and it’s best proved by economics (in other words the market price over decades of fruit or wine from certain parcels or zones) and by the comparisons we might be able to make between such winemaking fruit or such wines.

The further you go up the quality pyramid, in other words, the more the precise physical and chemical environment for the rooted vine seems to matter. Germany’s finest slate vineyards confirm that as, of course, do Burgundy’s limestone and marl sites, and Bordeaux’s gravel sites. Getting to this level of renown is work in progress for the world’s schist vineyards, but I don’t doubt that the finest wines of the Douro, of Priorat and of certain zones of Southern France will get there eventually. Then we’ll know more. There’s an exciting century for schist growers ahead.

Tasting wines grown on schist

Here are notes for the six wines of the 20 tasted which I scored at 89 or above from this blind tasting peer group (most cost less than 20 euros). Note that no wines from Priorat or the Douro were included in the tasting.

White wines

Caves de l’Estabel, Cuvée Fulcrand Cabanon, Clairette du Languedoc 2015

Well, here’s a surprise! This co-operative-made wine from the schist vineyards of Cabrières and the historic Clairette grape variety was the best of the whites for me, with sappy, vegetal aromas and convincing wealth, fullness and nuance on the palate. Its soft nougatine charm is amply balanced by some vinous structure and drive from the old vines … and the schist soils? (Great value at 9 euros from the cooperative.) 91

Domaine Pieretti, Marine, Vin de Corse Coteaux du Cap Corse 2015

This pure Vermentino wine from the far north of the island had pretty aromas of honey, dry straw and flowers and a fresher, zestier style than many of its Languedoc counterparts. The palate was fresh and resonant, too, with a little pear and lemon lurking behind the honeyed tones. 89

Red wines

Domaine Augustin, Adéodat, Collioure 2015

This wine, made by Marc Parcé’s son Augustin from old-vine vineyards complanted with both red and some white varieties, is clear, pure, limpid and vital, with ample fresh red fruit on the palate lent complexity by the scents and flavours of bitter-edged herbs; the zesty purity persists to the end. Southern finesse exemplified. 89

Les Vignerons de Maury, Nature de Schist, Maury Sec 2014

This wine showed how lucky Roussillon was to escape the Languedoc September torrents in 2014. Dark in colour, cherry-ripe in aroma, and with beautiful spicy-meaty amplitude on the palate. Once again, there was plenty of freshness and life here keep this delicious red dancing through the mouth. 89

Domaine des Païssels, Les Païssels, St Chinian 2015

An outstanding cuvée from young growers Vivien Roussignol and Marie Toussaint — and a convincing account of the potential of St Chinian’s schist zone. This blend of Carignan, Syrah, Grenache and Mouvèdre has floral and plum scents and a deep, textured, bitter-perfumed palate which both lingers on the tongue, revealing hidden density and richness, but leaves it clean and fresh thanks to the cleansing effect of the bitter herbal flavours. (Fine value at 13.50€ from St Chinian’s Maison du Vins.) 91

Domaine Pieretti, A Murteta, Vin de Corse Coteaux du Cap Corse 2015

A second impressive wine from the talented Lina Venturi-Pieretti, this fascinating wine is relatively light in colour, with intriguing floral and almondy aromas. After this, the gutsiness of the palate comes as a surprise: cherry-cream and plum fruits, but with substantial tannic ballast and a fine, lingering, meaty finish. It’s made from the variety locally called Alicante – though this has nothing to do with Alicante Bouschet, and describes a form of Grenache. 91