The Loire is a climate gradient with a court on it

The Loire is the longest river in France and the last thing anyone expected it to be: a boundary between two climates that happens to be made of water. From Nantes, where the estuary smells of salt, to Sancerre, five hundred kilometres inland, the same river runs through two different weathers. Muscadet is picked at eleven per cent potential alcohol because it has to be; Sancerre ripens to thirteen because the continent has taken over from the ocean by then.

That gradient is what the river has left. For four hundred years it had something more valuable: it was the road.

Two trades, one river

Wine floats. That single fact made the Loire a commercial artery in the Middle Ages, because a barrel could go from Touraine to Nantes on a flat-bottomed gabare for a fraction of what it cost to move it by cart. Downstream went the wine, and from Nantes it went to Brittany, to England, to the Dutch buyers who came for the white wines of Anjou.

Upstream went the court. In the fifteenth and sixteenth centuries the kings of France lived on this river — Charles VII at Chinon, Louis XI at Amboise, François I between Blois and Chambord — because it was the axis of the kingdom and because it was where the money and the roads were.

The châteaux sit where the two trades met, and that is not a metaphor about beauty. A château needs a river port, a bridge, a toll and a supply of stone; the wine trade supplied the traffic that paid for all four. Read the valley as a logistics corridor with excellent architecture, and it stops being a fairy tale and starts being an economy.

Then the road failed

The Loire is a bad river to navigate, and it always was. Its flow is wildly seasonal: in summer the water can drop so far that the gabares could not pass the sandbanks, and in winter the same river could rise six metres and take the bridges with it. The great floods of 1856 and 1866 are still the reference points; the levées — the long embankments that line the valley — were built and rebuilt for eight hundred years to keep the river in its bed.

So the trade went looking for a better route. The Canal de Briare, finished in 1642, was the first summit canal in Europe and connected the Loire to the Seine; the Canal latéral à la Loire followed in 1838, running beside the river it could no longer trust. Then the railway arrived — Paris to Orléans in 1843, to Tours in 1846, to Nantes in 1851 — and the river trade collapsed within a generation.

This is the point at which a river becomes scenery. The châteaux that had been working buildings with tolls and warehouses became monuments; the valley became something to look at, and eventually something to list.

What the river still sells

When the boats stopped, the vineyards stayed, and their logic became visible. Along one river, in one appellation system, four different wines: Muscadet at the estuary, where the Atlantic keeps the autumn warm and the grapes are picked lean to keep the acidity that oysters need; Anjou and Saumur in the middle, where chenin makes dry, sweet and sparkling wine from the same vine; Touraine, where cabernet franc ripens to a red the north of France can actually make; and Sancerre and Pouilly, five hundred kilometres inland, where sauvignon blanc is picked two weeks later and tastes of flint.

The soil changes too, of course — schist, limestone, gravel, tuffeau — but the dominant variable along the Loire is distance. It is the only French wine region whose identity is a direction: you can taste the river by drinking from west to east.

The stone that came out of the bank

One material ties the whole valley together, and it is the reason the châteaux and the cellars look as they do. Tuffeau is a soft, white, chalky limestone that lies in thick beds along the river. It was quarried out of the hillside, which left enormous underground rooms; it was light enough to be lifted into walls, which is why the châteaux are white; and it is porous enough to hold a steady humidity, which is why those rooms became wine cellars.

So the same quarry produced the building above and the cellar below. In parts of the valley people lived in the quarries — the troglodyte houses of Saumur and Touraine are not a folk tradition, they are what happens when you need a house and you have already dug a very good one getting stone for someone else's.

How to taste a river

Open three bottles in one evening: a Muscadet, a dry Vouvray, a Sancerre. Do not think about grape varieties first. Think about the distance each wine travelled from the sea. The Muscadet should taste of salt and be almost aggressive in its acidity; the Vouvray should be rounder, with a waxy, honeyed middle; the Sancerre should be the driest and the most mineral, with a finish that feels like a stone rather than a fruit.

Three wines, one river, no shared grape. That is the Loire's argument: in most of France the land decides the wine, but here the weather decides, and the weather is a function of how far inland you have gone.

This is entry 05 of Land & Terroir in About France. The pillar's argument — that France wrote soil and weather into law — is set out on the pillar page.