Sémillon is relatively easy to grow and has vigorous vines which can easily produce ten to fifteeen tonnes of grapes per hectare if not kept under control. The grape berries are thinned skinned, small, round to oval and greenish colored. It is fairly resistant to disease, except for rot. The grape ripens early in warmer climates. Due to the thin skin there is a risk of sunburn in hotter climates as well as splitting after heavy rain. It is best suited to areas with sunny days and cool nights.
Sémillon is one of only three approved white wine varieties in the Bordeaux region. The grape is also key to the production of sweet wines such as Sauterne
In Bordeaux it is blended with Sauvignon blanc and Muscadelle. When dry, it is referred to as Bordeaux blanc and is permitted to be made in the appellations of Pessac-Léognan, Graves, Entre-deux-mers and other less-renowned regions. In this form, Sémillon is generally a minor constituent in the blend.
However, when used to make the sweet white wines of Bordeaux (such as those from Sauternes, Barsac and Cérons) it is often the dominant variety. In such wines the vine is exposed to the "noble rot" or what may be called the "positive affect" of Botrytis cinerea which reduces the water content of the fruit, concentrating the sugar present in its pulp. In this case Botrytis cinerea causes the grapes to shrivel and the acid and sugar levels to intensify.
In Australia, Semillon is produced both as dry unwooded and wooded table wines and as botrytis affected "stickie" dessert wines. In the Hunter Valley of New South Wales, Semillon is made into an initially subdued unwooded wine of relatively low alcohol (10-11%). But with bottle age it developes into a full flavoured toasty honeyed wine which is a style unique to Australia.
This year we made our first 100% Semillon from our relatively young vines.
It has been in the tank now maturiung for 4 months and is just starting to develop the typical Semillon nose ie. grass/hay/apples. Alcohol level is around 10.5% and intially we were quite concerned at it's high acidity. But on storage there has been quite a precipitation of tartrate and TA has dropped and pH has increased. We will be ready to bottle in a month or so.