During his 15 years at Kearney, Jensen identified recent agricultural science graduates and hired them as staff research associates to work with him in the field and in his lab. He trained them on the most recent plant science research techniques, imparting skills for future careers as farm advisors.
UC Cooperative Extension advisors that worked with Jensen include George Leavitt, retired UCCE advisor in Madera County, viticulture; Harry Andris, retired UCCE advisor in Fresno County, tree crops; Bob Beede, UCCE advisor in Kings County, tree crops; Larry Bettiga, UCCE advisor in Monterey County, viticulture; Rhonda Smith, UCCE advisor in Sonoma County, viticulture; and Mary Bianchi, UCCE advisor in San Luis Obispo County, horticulture.
“Jensen was soft-spoken, had a good sense of humor and honest to a fault,” said Fred Swanson, the former director of Kearney. “He was an outstanding researcher, an accomplished photographer and has made a greater impact than anyone I’ve known by investing himself in other people.”
Jenson was raised on a farm in Weedpatch, Kern County. He earned a bachelor’s degree in soil science at UC Berkeley in 1942, then served for three years in the U.S. Army. He later earned a master’s degree in horticulture from UC Davis.
In 1947, Jensen was hired as an assistant farm advisor by UC Cooperative Extension in Tulare County at a salary of $3,600 per year. In 1972 he was promoted to viticulture specialist at Kearney.
As both a farm advisor and specialist, he worked to develop and obtain registration for commercial products to benefit the state’s grape growers, such as plant growth regulators and many other critical agricultural chemicals. Jensen’s detailed research on gibberellic acid applications helped identify optimal rates and timing that had eluded previous UC researchers. His work on bloom time applications have become an industry standard. Jensen also did the initial work on ethephon, a plant growth regulator used to enhance and improve fruit color. Jensen developed the use of ethephon to enhance raisin maturity, which almost eliminated the loss of raisin crops from early rains.
Jensen researched cultivar selection, vine spacing, trellising and integrated pest management. An early promoter of IPM practices, his contributions were instrumental in production of the UC Grape Pest Management Manual. He was the author or co-author of more than 250 publications and his scientific work is referenced in textbooks, journals and other viticulture publications. Jensen was a longtime editor of the scientific journal American Enology and Viticulture and was a world authority on table grape production.
Jensen retired from UC Cooperative Extension in 1987, but continued to conduct research and extension work for decades as an emeritus viticulture specialist and private viticulture consultant. In honor of his life-long body of work, Jensen received the Merit Award from the American Society for Enology and Viticulture in 2001. He was recognized for his contributions to California’s table grape industry at the 6th International Table Grape Symposium in 2010.
Jensen is survived by his wife of 27 years, Thelma Lile Essex, two daughters, three step-children and many grandchildren and great-grandchildren. A memorial service will be at 11 a.m. April 28 at Quail Park Retirement Village, 5420 W. Cypress Ave., Visalia, Calif.