Bierzo is a Spanish Denominación de Origen (DO) for wines located in the northeast of the province of León (Castile and Leon, Spain) and covers about 3,000 km². It borders on the provinces of Orense, Lugo and Oviedo in the north and in the south on areas of La Montaña, la Cabrera and La Meseta, in Léon. The area consists of numerous small valleys in the mountainous part (Alto Bierzo) and of a wide, flat plain (Bajo Bierzo). The DO covers 23 municipalities including the largest town of the area, Ponferrada, (pop. about 70.000).
The Bierzo DO has a special microclimate which is beneficial for viticulture. On the one hand it is similar to the climate of Galicia with regard to humidity and rainfall, and on the other it is also similar to the hot, dry climate of Castile. The low altitude also helps to prevent late frosts and means that the grape harvest is usually about one month earlier than in Castile. The average annual temperature is around 12°C, with the minimum in winter of 3.5°C and maximum in summer of 24°C. The average annual rainfall is just over 700 mm, and the vines receive about 2,200 hours of sunshine per annum.
The wines produced under the Bierzo DO must be made only with the varieties that are authorised by the Consejo Regulador (Regulatory Council). Red grapes: Mencia, Garnacha Tintorera, (experimental: Tempranillo, Merlot, Cabernet Sauvignon) White grapes: Doña Blanca, Godello, Palomino, (experimental: Malvasía, Chardonnay, Gewürztraminer) The experimental varieties can only be used for crianza and reserva wines, and may not comprise more than 15%.