Guide
Noble rot, and why a hectare of Sauternes fills half the bottles
A fungus, a cold river meeting a warm one, and a rule that makes a machine illegal.
The short answer
Botrytis cinerea shrivels a ripe grape and concentrates what is left. The Sauternes cahier (the cahier des charges, the appellation’s official rulebook) requires grapes picked over-ripe, by hand, in successive passes, which caps the crop at 25 hectoliters a hectare against the Médoc’s 55, and asks 221 grams of sugar a liter before the wine may carry the name.
The mechanism
The river Ciron, a small tributary of the Garonne, runs cold under trees and joins the warmer Garonne at the edge of the appellation. On an autumn morning that meeting makes mist; the mist lifts by midday and the sun comes through. Damp night, dry afternoon, repeated: that is the condition Botrytis cinerea needs to take a ripe grape and puncture it rather than rot it. Water leaves, sugar and acid stay, and the berry shrinks to something that looks ruined and tastes concentrated.
The cahier des charges names the fungus by its Latin name. It is not a house style. It is written into the law of the place.
Why the crop is so small
| Sauternes | Médoc | |
|---|---|---|
| Yield allowed | 25 hectoliters a hectare, ceiling 28 | 55 |
| Sugar required in the grapes | 221 grams a liter | Far less |
| Natural alcohol | 15%, of which 12% must survive fermentation | 11% |
| Sugar left in the wine | 45 grams a liter at least | Under 3 |
| Harvest | By hand, over-ripe, in successive passes | Machine allowed |
Successive passes is the phrase that does the work. The rot does not arrive evenly, so the pickers go through the same rows again and again over weeks, taking only what is ready. A machine cannot make that choice, so the rule makes the machine illegal without ever naming it.
What it costs
The same hectare that would fill 7,000 bottles in the Médoc fills about 3,000 here, and in a year when the rot does not come cleanly it may fill none at all worth selling. Estates in Sauternes declassify entire vintages more readily than anywhere else in Bordeaux, because the alternative is to bottle something the name cannot carry.
One recent change worth knowing
The cahier in force was amended by the order of March 25, 2026, which brought the end of aging forward to March 15 and the release to April 1 of the year after the harvest. Before that a Sauternes could not be sold until July.
Where to go next
Sources: Fédération des Grands Vins de Bordeaux, cahier des charges Sauternes · INAO, cahier des charges Sauternes