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 Carignan that was first trialed by Dr. Olmo in 1936 before being released in 1948. The grape is primarily used in blending, adding color and tartness, but producers such as E & J Gallo Winery have produced varietal wines from the grape. According to wine expert Jancis Robinson, Ruby Cabernet can have some aromas reminiscent of a young Cabernet Sauvignon with the color of a Carignan but it lacks the structure and body to produce premium wines.
In California, the variety is widely planted in the Central Valley where it can withstand the hot continental climate of the valley and still produce harvest yields of 6 to 9 tons an acre. Outside of California, the variety can also be found in Australia, Argentina, Chile, Israel and South Africa.