Albert Winkler; Authority on Viticulture

Albert J. Winkler, one of the nation’s foremost authorities on viticulture, whose research contributed to the growth of California’s wine industry, has died in a Davis convalescent hospital. He was 95.

In 1938, Winkler developed a system for classifying the most desirable wine grape growing areas in California by using “degree days”--calculating how many days in the April-October growing season each region registered the best temperatures for maturing vines.

The system is still in use today.

A Texas native who earned his doctorate in horticulture at UC Berkeley in 1921, Winkler spent much of his career as a specialist in wine grapes and wine making.

But during the Prohibition era, 1919-33, he switched his research to table grapes and in the late 1920s pioneered a sulfur dioxide gassing process that made it possible to ship and market California grapes in the East.

After Prohibition, Winkler returned to wine grape research. A UC Davis faculty member for four decades, he headed the university’s department of viticulture from 1935 to 1957.

In his work on degree days, Winkler identified five zones or regions throughout the state, with I and II the best for nurturing wine grapes. His Zone I, including Oakville in the Napa Valley, was considered comparable to Burgundy, a major wine center in France. His Zone II, including most of Napa and Sonoma counties, was compared to Bordeaux, another historically fine wine-producing section of France.

Winkler’s book “General Viticulture,” published in 1962, became an international text on wine grapes and was translated into several languages.

Winkler continued his research even after he retired from the UC Davis faculty.

A memorial service was held Tuesday in Davis for Winkler, who died Aug. 29 of natural causes.

Winkler is survived by two daughters, Marjorie Morris of Sacramento and Ethel Plocher of Watsonville.

His wife of 69 years, Pearl Buehrer Winkler, died last year.