Folle blanche

Folle blanche was the grape of Cognac before phylloxera, and the change of that fact is the whole of its story. It gives a wine so acidic and so low in alcohol that it is barely drinkable, which is exactly what a distiller wants, because acidity carries aroma through the still and low alcohol means a clean spirit. It made the classic brandy of the region for centuries.

Phylloxera ended that. Grafted onto American rootstock, Folle blanche turned out to be highly prone to grey rot in the tight bunches it produced, and Cognac replaced it almost entirely with Ugni blanc, which is more robust and does much the same job. A small amount survives in Armagnac, where it is credited with a finer spirit.

As a wine it still exists at the mouth of the Loire, where it is called Gros Plant and makes a fiercely dry, sharp, low alcohol white sold beside Muscadet and priced below it. It is also the parent of Baco blanc, the hybrid bred specifically to replace it in Armagnac after phylloxera.