The blend used for White Graves and Sauternes and rarely encountered outside France. In the great dry whites of Graves, Sauvignon Blanc tends to predominate in the blend, although properties such as Smith Haut Lafite use 100% Sauvignon Blanc while others such as Laville Haut Brion have as much as 60% Sémillon in their final blends. Sauvignon Blanc wines can lose their freshness and fruit after a couple of years in bottle - if blended with Sémillon, then the latter bolsters the wine when the initial fruit from the Sauvignon fades. Ultimately Sauvignon Blanc gives the wine its aroma and raciness while Sémillon gives it backbone and longevity.
In Sauternes, Sémillon is dominant, with Sauvignon Blanc playing a supporting role - it is generally harvested about 10 days before Sémillon and the botrytis concentrates its sweetness and dampens Sauvignon Blanc`s naturally pungent aroma. It contributes acidity, zip and freshness to Sauternes and is an important component of the blend.