Pourriture noble (in English: ‘the Noble Rot’) is a parasitic infection of a grey fungus called Botrytis cinerea. Botrytis affects over 80 different types of plants in the Pacific Northwest, including strawberries, tomatoes, and bulb plants. On most plants, botrytis will rot the stems, fruit, and crowns. The plant tissue will begin to collapse in on itself.
Even in wine grapes, botrytis can pose a major hazard. In extremely damp conditions, botrytis will fester, leading to unusable grapes that have been destroyed by ‘the Gray Rot’. Botrytis qualifies as ‘the Noble Rot’ when wet conditions bring botrytis spores, but subsequent dryness leads to a partial raisining process. As the mold enters the skin of the grapes, its spores begin to germinate. The water inside the grape evaporates, leading to a concentrated sugar content.
The Noble Rot is important for several distinctive dessert wines, including ice wine. For the Walla Faces 2008 Riesling Ice Wine, the cultivation of botrytis added to the sweetness of the finished product. The use of botrytis also increased depth and complexity, especially for Riesling varietals. The deep golden color of the Walla Faces Ice Wine epitomizes the complex beauty of a botrytized wine.
It’s not exactly clear when botrytis was first used in winemaking. Historical documents show that botrytis showed up in Hungarian literature as early as 1576. By 1730, botrytis was so integral to Hungarian winemaking that vineyards were rates based on the proclivities for cultivating the fungus.
The Germans, however, have a special legend about its origin. They say that the Noble Rot was discovered independently in Germany in 1775. According to the myth, the Riesling farmers were required to wait for their estate owner’s go-ahead in order to harvest. When the messenger delivering the order to harvest was robbed en-route, the farmers were forced to watch the grapes slowly begin to rot. Assuming the grapes to be worthless, the vineyard owner, Heinrich von Bibra, gave the grapes to the German peasants, who used it to make the first late-harvest Riesling.
Now, the use of botrytis is hardly an accident, with many winemaker intentionally infecting their vineyards in order to achieve the complexity and sweetness that proper use of botrytis ensures. (In the Pacific Northwest, however, botrytis is usually introduced naturally.)