Viognier is a white wine grape. It is the only permitted grape for the French wine Condrieu in the Rhone valley. Viognier can be a difficult grape to grow because it is prone to powdery mildew. It has low and unpredictable yields and should be picked only when fully ripe. When picked too early, the grape fails to develop the full extent of its aromas and tastes. When picked too late, the grape produces wine that is oily and lacks perfume. Winemakers in the Condrieu often pick the grapes with a level of sugar that will produce wine with alcohol in the 13% range. When fully ripe the grapes have a deep yellow color and produce wine with a strong perfume and high in alcohol. The grape prefers warmer environments and a long growing season, but can grow in cooler areas as well.
In France, the Mistral has a distinct effect on the Viognier vineyards in the Northern Rhone. The wind tempers the Mediterranean climate of the region, and cools the vines down after the severe heat of summer.
Wine expert Remington Norman has identified two distinct strains of Viognier — an “Old World” strain, most common in Condrieu, and a “New World” strain, which is found in the Languedoc and other areas. Although made from the same grape, the two strains produce distinctly different wines.
The age of the vine also has an effect on the quality of the wine produced. Viognier vines start to hit their peak after 15–20 years. In the Rhone, there are vines at least 70 years old.