Andrew Jefford
Aremarkable photograph: a soil pit dug into a vineyard, perhaps 1.5 metres deep, with about 70cm of rich, mixed topsoil, uncompacted but lively with organic matter. Then – clay. Solid clay. The pit had obviously been open for a while, and the vines above were in summer garb – hence the cracks in the clay, ‘big enough,’ said the photographer, ‘to put your hand in.’
No ordinary photographer, moreover: this was Jacques Fanet, former assistant director of both the Institut National des Appellations d’Origine (INAO) and the International Organisation of Vine and Wine (OIV), as well as author of Great Wine Terroirs, a useful geological adjunct to the understanding of wine globally. ‘If there weren’t vines there,’ Fanet added, ‘no viticultural consultant in France would ever recommend planting these soils as a vineyard.’ The vineyard was that of Château Petrus in Pomerol.
The subject of the day was, in fact, schist, but Fanet had also presented some material relating to the late Gérard Seguin’s influential Bordeaux terroir research, which stressed the importance of water relations for high-quality wine-growing soils. The ability of soils based on schist to drain freely in times of abundant rainfall but to retain moisture at depth, thus providing vines with a consistent but moderate water supply, is something that they have in common with classic Bordeaux gravels, free-draining with hidden inner lenses of moisture-retaining clay and sand.
A formula for great wine? You might think so – but then along comes Petrus to break every rule. Its root-clenching montmorillonite clay swells and shrinks like bellows with moisture, and often needs amelioration for viticultural use. Thumbs down.
The Terroirs de Schistes organisation’s study and tasting day in November brought together growers from different schist zones in France and beyond. I’d taken part in a previous event in 2018, comparing unaged wines grown in the schist and limestone sectors of St-Chinian in Languedoc. At the
November 2019 event, we tasted a series of unaged pure-Carignan wines in pairs, in order to hunt down differences of profile. Were schist tannins more elegant, and limestone tannins fatter and fuller? Was schist acidity more prominent, and limestone acidity more unpredictable, sometimes less seamlessly incorporated? Were the limestone wines richer in general, the schist wines slimmer and drier? Or, um, was it the other way round? Firm conclusions eluded us. The thing we all agreed on was that outstanding wines could be grown on both soil types.
Perhaps, though, we should have thought more deeply about Fanet’s Château Petrus photograph. What if Petrus’ part of Pomerol is a magnificent place to make fine Merlotbased red wine (assuming qualitative viticulture and sensitive vinification) because of what’s happening above rather than below: the nuances of light and solar radiation, of wind and air currents, of rainfall, of diurnal variations over an entire season? Those unique and precious combinations mean that the vines are happy there – so happy that they’ll make do with what lies below, be it gravels or solid clay. Yes, what lies below gives Petrus the chunky, forceful or burly character which tasters repeatedly notice, and which they value so highly – but the same clay in a less propitious site would disappoint bitterly. It’s the site, not the soil, which is qualitative. Pomerol (or Faugères, or Priorat) might, in fact, be endowed with different soil combinations and be no less qualitative. Different, but still fine.
There is, I think, a chance that artificial intelligence will eventually help us get to the bottom of all of this, both in terms of understanding physical inputs and delivering analyses of what it is in a wine liquid that sends us into raptures, winnowing data sets in a way that is beyond us at present. Will it, though, help us find more of these raptures? I wouldn’t count on a second Petrus just yet.