Wine · Terminology

Botrytis

Botrytis cinerea — grey rot when it goes wrong, noble rot and the world's great sweet wines when it goes right.

Botrytis cinerea is a fungus with two faces. Attacking healthy or unripe grapes in wet conditions it becomes grey rot — a straightforward disaster that taints the fruit and ruins the crop. Attacking ripe, healthy white grapes under the right alternating weather, it becomes noble rot, the foundation of the greatest sweet wines in the world.

The mechanism is dehydration. The fungus punctures the skin, water evaporates, and the berry shrivels — concentrating sugar, acid and flavour while adding its own honeyed, saffron, dried-apricot character and a distinctive glycerol richness.

In practice

  • Needs damp misty mornings (for the fungus) followed by dry sunny afternoons (to stop it running away into grey rot).
  • Requires geography: a river or lake supplying autumn mist — the Ciron in Sauternes, the Bodrog and Tisza at Tokaj, the Mosel and Rhine.
  • Berries are picked in successive passes (tries), sometimes berry by berry, over weeks.
  • Yields collapse: Château d'Yquem famously reckons on roughly one glass of wine per vine.

Where you'll meet it

Noble rot versus grey rot

Noble rot Grey rot
Fruit Ripe, healthy, thin-skinned whites Unripe, damaged, or black grapes
Weather Misty mornings, dry afternoons Persistent damp
Effect Concentration, honey and apricot notes Mouldy, bitter taint; colour loss in reds
Outcome Great sweet wine Crop loss

Black grapes are far more vulnerable to the bad version, which is why noble-rot wines are essentially always white.

The sweet-wine family

Botrytis is only one of four routes to a concentrated sweet wine, and exams routinely ask you to separate them:

  1. Noble rot — fungal dehydration. Sauternes, Tokaji, TBA.
  2. Late harvest — extra hang time, sugar accumulation, some passerillage.
  3. Freezing on the vine — Eiswein, water removed as ice.
  4. Drying after picking — passito / appassimento, as in Vin Santo and Recioto.

Browse the full wine terminology A–Z →