The largest vineyard plot of Léoville-Las Cases known as the Grand Clos, are located in the norther portion of the St-Julien with only the Juillac tributary separating its vineyards from those of Latour. 97 Hectares are planted to 65 % Cabernet Sauvignon, 19% Merlot, 13% Cabernet Franc and 3% Petit Verdot. The vineyard underwent major replanting during the 1950s after the frost. Today the vines average 30 years of age.
Grapes are harvested by hand, crushed and then may be fermented in temperature controlled wood, concrete, or stainless steel vats of varying size depending on the style of the vintage. Starting in 1987, Léoville-Las Cases began employing a state of the art, reverse osmosis machine to help extract excess water from the grape must. Use of this technique is considered controversial by some people. However today, that technology is by many of the top Bordeaux Chateaux. People questioning the technologies effect of wine need only to taste 1990, 1996, 2000 and other top years. Those are all better vintages for Leoville Las Cases, than previous famous years like 1982. According to Delon, reverse osmosis is only used in select vintages.
Leoville Las Cases produces a structured style of Bordeaux wine. In the top vintages, buyers should be aware that these years of Leoville Las Cases take 15-20 or more years to develop and shed their tannic structure. At that point in time, the Bordeaux will wine display cedar, cassis, dark berries, truffle and tobacco notes in a style that often resembles a First Growth Pauillac.