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Plant Focus

Quercus macdougallii
A rare oak endemic to the Sierra Juárez in Oaxaca

Cork Wars in World War II: Oaks, Espionage and National Security

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David A. Taylor

Published May 2019 in International Oaks No. 30: 295–300


This paper shares a compelling piece of oak history and California history. In the 1940s, when cork was a modern material crucial to America’s war effort, youth clubs and state governors were planting Quercus suber (cork oaks) to make the country free of dependence on foreign sources.
By 1940 the United States imported nearly half the world’s production of cork, for industries ranging from bottle caps to automobiles, flooring, various forms of insulation, and bomber airplanes. When Germany blockaded the Atlantic trade, the shortage of cork from Europe became a threat to national security. Then when a factory fire in Baltimore stirred an FBI investigation for sabotage, the entire industry was pulled into the war effort, from corporate espionage in Portugal to a nationwide tree-growing campaign.
The paper draws on research from the author’s new book, Cork Wars: Intrigue and Industry in World War II (Taylor 2018). It looks at the system from Portugal’s montado oak forests to the American tree-growing campaign, in which a dozen state governors brandished shovels to promote a patriotic cause. In addition to telling this story, the paper shares the discovery process and research process, from conducting survivor interviews to uncovering declassified records in the National Archives.


Quercus suber, Crown Cork and Seal, Woodbridge Metcalf, McManus Cork Project