White wine the death knell of northern viticulture. The vine disappeared from northern Germany and Baden, and the maximum altitude for viticulture descended to 220 metres. Hans-Jürgen Otto noted that: "all the vineyards suffered and decreased in area". In England the vine also disappeared. The less early vineyards preferred to select white varieties of grapes because, even if unripe, white grapes allowed wine that was a little sour to still be consumable, while red grapes do not give enough colour and green tannins make the wine bitter. The interruption of the fermentation by a cold winter led to the discovery of the
Olmo grapes Olmo grapes Olmo grapes are wine and table grape varieties produced by University of California, Davis viticulturist Dr. Harold Olmo. Over the course of his nearly 50-year career, Dr. Olmo bred a wide variety of both grapes by means of both crossing varieties from the same species or creating hybrid grapes from cultivars of different "Vitis" species. Over 30 new grape varieties were created by Dr. Olmo and introduced to the California wine and table grape industries. Ruby Cabernet is the most notable and widely planted Olmo grape. It is a crossing between the "Vitis vinifera" varieties Cabernet Sauvignon and