Resting beneath the shady shelter of my favorite, spreading oak tree on a recent neighborhood walk, I follow the persistent tapping to a nearby utility pole.

A bobbing red crown reveals the source: an acorn woodpecker hard at work in her colony’s granary. Her long black beak skillfully stuffs an oblong green acorn from “my” oak into holes she’d drilled for the winter days ahead, when she and her colony mates will revel in their conveniently stocked pantry.

Valley Oak San Jose - POST
Silicon Valley was once covered in ancient valley oaks, the largest of the oak species. Ranching, orchards and urban development have slowly replaced these native giants. Photo courtesy of the San Jose Public Library

A mournful duskywing butterfly flits above my head into a clump of oak mistletoe hosted by my oak (mostly harmlessly) and offering tasty white berries to western bluebirds and oak titmice. At my feet march industrious ants, farming the copious leaf litter.

Clearly, I’m not the only oak fan here!

California’s 20-plus indigenous species of oaks –blue, black, coast live, and valley predominate in the Santa Clara Valley – are “foundational species” that provide food and nesting habitats to a web of thousands of plants, insects, invertebrates and mammals. Not to mention a multitude of street and city names: think Oakland, Oakhurst, Thousand Oaks, Paso del Robles (Spanish for… yep, oaks).

Indigenous Californians relied for thousands of years on oak acorns as a dietary staple. But they, and early European explorers, and 19th-century Americans who once marveled at “the Valley of the Heart’s Delight,” would never recognize our present-day landscape. Centuries of timbering, farming, modern industry and recent tastes for non-native street trees have felled, dug up, paved over and replaced the vast majority of our native oak woodlands.

POST’s project partner, the San Francisco Estuary Institute (SFEI), aims to change that with its “Resilient Silicon Valley” project. Their mission is to “re-oak” urban Silicon Valley through community and private property planting, thereby maintaining the health and resiliency of our environment.

POST Office Oaks
The entrance to POST’s office in Palo Alto was recently re-landscaped to include native vegetation, including these two hearty oaks. Photo: Matt Dolkas

Not only do oaks support the most diverse habitat type in California, they are also drought tolerant, require little irrigation and are fire-resistant—a major benefit in the drier, warmer climate predicted for California. And they help clean our air by absorbing carbon and nitrogen.

SFEI’s guidelines, backed by extensive study and data collection, advocates re-oaking with new plantings and replacement of non-native, less hardy trees after natural die-out. Meanwhile, health maintenance and protection of existing oaks against Sudden Oak Death and other perils will provide a robust environment for continued growth—and food, nests, shade, and beauty for woodpeckers, butterflies, ants and human neighbors for years to come.

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About Post

Peninsula Open Space Trust (POST) protects open space on the Peninsula and in the South Bay for the benefit of all. Since its founding in 1977, POST has been responsible for saving more than 87,000 acres as permanently protected land in San Mateo, Santa Clara and Santa Cruz counties. Learn more

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