Most modern wine grapes are varieties of the species vitis vinifera, which is native to the Mediterranean region and central Europe. It is a widely adapted species and is grown on every continent except Antarctica. Most modern grapes based on v. vinifera are actually grafts onto North American rootstock of another species (such as v. labrusca), which was first done in the late 19th century after European vineyards were devastated by phylloxera.
When a single variety constitutes at least 75-85% of a wine (varying by law in country where produced), the result is a varietal wine named after the predominant grape. Many wines from the United States and Australia are produced as varietal wines. Wines with a mixture of grapes are known as blended wines. Blended wines are not inferior to varietal wines; in fact, most well known French wines are blends of different varieties of the same vintage. European wines (French, Italian, German, Spain, etc.) are named for the region rather than the grape varieties used, although only certain varieties may be used by law in certain blended wines.
The concept of terroir is very important in the production of fine wines. It encompasses all environmental factors that produce a certain product, including the types of grapes used, the elevation and shape of the vineyard, the soil conditions and chemistry, climate and seasonal conditions, and local yeast cultures. This is how very unique wines are made from essentially the same ingredients. Mass-produced wines typically favor consistency at a low price, so the terroir is minimized.
The aroma and flavor of specific grape varieties will vary from year to year based on seasonal growing conditions, especially heat and rainfall. A range of descriptors is given for each variety, but don’t expect all the various components to be in every vintage. Various wine resources describe the character of grapes depending on whether they were grown in cool, moderate or hot climates. This is why wine vintages will vary greatly, and some are more prized than others.
Grape varieties are typically grown for either red wine or white wine usages, although some can be used for both applications. Red wine gets its color (and tannin) from contact with red grape skins. Red grapes can make white wine if the skins are separated from the juice at pressing. Wines that are designed to age are often oaked, red wines more frequently than white. When judging pyments, keep in mind the character contributed by the grape juice and separate it from the fermentation, conditioning and age character that can vary. Mead makers will not always treat varietal grapes in the same way vintners will treat them, so stick to the varietal character of the grape more than the total impression of popular wines made from those grapes.
INFORMATION COURTESY BJCP SPECIAL INGREDIENT DESCRIPTIONS
(The description of Grapes from the BJCP Mead Exam Study Guide)