As Jancis Robinson says, ‘Sémillon is a very odd grape indeed’. It is capable of producing some of the greatest wines on earth, such as Château d’Yquem, a sweet wine from Sauternes in the Bordeaux region of France. It is in the sweet wines of Sauternes, blended with Sauvignon Blanc, that this grape reaches its finest expression, the classic proportions being 80% Sémillon and 20% Sauvignon Blanc. Often a third grape variety, Muscadelle, will also be a minor component.
The major secret to Sémillon’s success in Sauternes is that it is a thin-skinned grape, susceptible to noble rot, botrytis cinerea. Dr. Richard Smart, in The Oxford Companion to Wine, tells us that the causal fungus for this rot is botrytonia fuckelinia. Normally rot in the vineyard is the grape grower’s nightmare, but for making sweet wines this particular variety of rot reduces the juice in the berries (hence in German the sweetest, most expensive Rieslings, affected by noble rot, are labelled trockenbeerenauslese), leaving bunches of mushy, thoroughly rotten-looking grapes that frankly appear positively noxious and inedible. But from these rotten bunches you can squeeze tiny amounts of intensely sweet, concentrated juice to produce exquisite wine.
Sémillon is also grown in the Graves (still in Bordeaux, just north of Sauternes), where it is used to make dry whites, blended typically 50-50 with Sauvignon Blanc, matured in oak barrels. The top wines can develop over many decades. And all over the Bordeaux region, dry whites are produced from Sémillon/Sauvignon blends.
There is another manifestation of this variety that stands out for its excellence and interest. This is Hunter Valley Semillon. Here the grape is unblended, picked early, and needs bottle age to reveal its extraordinary quality. These wines are never oaked, yet after several years in bottle they take on a lanolin dimension to the flavour that is strangely reminiscent of oak-aged wines. They also acquire a waxy, fascinating texture.
It is Sémillon’s misfortune to be unfashionable, though it is still widely planted throughout the world. At one point it was the world’s most widely planted white grape variety. In 1822, 93% of all vineyard area in South Africa was planted with Sémillon. In 1979 it was still France’s second most planted variety (after Ugni Blanc, Trebbiano). Although it is in decline, it is still to be found in virtually all the vineyard areas of the world.
To sum up, Sémillon produces, at its best, extremely long-lived, subtly and intricately flavoured wines, both dry and sweet. It is often blended, most commonly with Sauvignon, but also, in Australia, with Chardonnay, and I have seen a successful Chenin Blanc/Sémillon blend from South Africa.
An underrated grape variety.