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Plant Focus

For this Species Spotlight we train our follow spot on an oak that is quite a star of the quercine scene: Quercus hypoleucoides (stage name...

Tracking Cork Oak and World War II History in the American West

Quercus suber is a Mediterranean oak, but some years ago I learned it had a curious history in North America. In the 1700s, Thomas Jefferson during his time in France came to admire cork and its properties. He planted cork oak acorns at Monticello many times, but they lost viability after the long ocean crossing.

For a century, American businesses imported cork stoppers from Portugal and Spain, where producers harvested it from trees every 8 to 10 years. In the 1890s a chance invention of composition cork (a thin layer of cork granules held together by adhesive) opened the way for manufacturing processes that used cork in a wide range of industries.

Cork oak grove at UC Davis
Cork oak grove at UC-Davis in 2018 © Skip Mezger

By 1940, the United States imported nearly half the world’s cork production, for making everything from bottle caps and automobile gaskets to bomber airplanes. When Nazi Germany blockaded all Atlantic trade and cut off cork imports from Europe, the shortage was deemed a threat to U.S. national security. So Charles E. McManus Sr., the CEO of industry leader Crown Cork and Seal, launched a nationwide tree-planting campaign dubbed the McManus Cork Project to grow cork oaks for domestic production.

Through World War II, young 4-H club members and garden clubs from coast to coast joined in tree-planting efforts promoted by Governors’ proclamations and Arbor Day celebrations. For the young people who planted 5 million acorns, the seedlings represented self-reliance and a patriotic effort they could grow.

NC 4H Club members
Promotional photo of 4-H club members ready to plant cork oak 
© Swem Library

For a book about that period, I spoke with several people from families who recalled planting the exotic Q. suber seedlings. I became curious: What became of those Q. suber seedlings planted over 70 years ago? I could find only a few survivors on the East Coast. In the Southwest and West Coast there seemed to be more. At the University of Arizona Campus Arboretum in Tucson, Elizabeth Davison, the founding director, told me how Steve Fazio led the cork oak plantings on campus in the 1940s. Decades later, Davison commemorated a survivor of those plantings as a Heritage Tree for Arizona.

In 1944, for Arbor Day in California, Governor Earl Warren (later Chief Justice of the U.S. Supreme Court) planted a cork oak seedling on the capitol grounds in Sacramento. Woodbridge Metcalf, a forestry professor at the University of California at Berkeley, led the McManus Cork Project’s activities in the state. Metcalf inventoried dozens of Q. suber trees, from Northern California south to Los Angeles, that had survived for nearly a century. He led teams in gathering acorns from the largest mature individuals and assessing the quality of their cork and how the trees adapted to local conditions.

Earl Warren swings a shovel
Governor Earl Warren swings a shovel on Arbor Day, 1944 
© Swem Library

I posed questions to botanists at UC Davis, and Skip Mezger confirmed Woodbridge “Woody” Metcalf managed the planting of the cork oaks near Mrak Hall in the UC Davis Arboretum. “There appear to be about 11 left from the original plantings,” Mezger wrote. He noted that some of the cork oaks were removed in the 1960s to make way for construction. He sent a photo of the Arboretum’s cork oak grove as it looks now.

Warren Roberts, superintendent of the UC Davis Arboretum for more than 35 years, added that he knew of other big Q. suber individuals – including two of the oldest and biggest on campus, and a few over a century old.

“The biggest and maybe oldest cork oak in California is on the grounds, north side of the California State Mental Hospital, southeast of Napa,” Roberts wrote, referring to Napa State Hospital. He suggested I be discreet if I planned to visit and take any photographs though, “or you’ll get a visit from the guards.”

I look forward to sharing more of this story at the International Oak Society conference in Davis and visiting the Davis cork oak grove myself.

David A. Taylor is the author of Cork Wars: Intrigue and Industry in World War II (Johns Hopkins University Press, 2018) and other books. Visit www.davidataylor.com.