Quercus lobata
valley oak, roble
Quercus lobata, once reigning over the rich alluvial floors of California’s interior valleys, is the state’s classic white oak, much as Q. alba is to the forests of the eastern United States and Q. robur to the woods and parklands of Europe. Its deeply lobed leaves earned it the name lobata from a botanist who never beheld the living tree. Likely the tallest of North American oaks, the largest known stands in Covelo, California, 153 feet high and more than 28 feet in girth.
Valley oak and coast live oak are the principal native oaks of main campus. A monumental specimen grows between 24 and 25 Olmsted Road in Escondido Village; another fine example is between 708 and 712 Salvatierra Street. The most conspicuous exemplar on central campus, north of the Bookstore, is not looking particularly vigorous.
Frank Lloyd Wright designed Hanna House (737 Frenchmans Road) in 1936, nestled among a grove of scrawny valley oaks and a Monterey cypress. With attentive care over nearly a century, including the propping of great outstretched limbs, the oaks have matured into magnificent creatures of immense presence.
Valley oak limbs are sometimes adorned with clumps of mistletoe, most visible in winter when the branches are bare, as well as with round, brown, golf ball–sized oak apples – galls formed from the plant’s own tissue in response to wasps depositing their eggs. Other smaller galls, some intricately shaped or brightly colored, may be found on their leaves. Tiny jumping galls are sometimes seen under the tree, the larvae inside contracting their muscles and pressing against the gall walls to bounce towards shade – much like a Mexican jumping bean – where they later complete their development.
Illustrations: Jasper Ridge Quercus lobata on Flickr.
About this Entry: Authored Aug 2025 by Sairus Patel.
