Quercus robur | Palo Alto
English Oak (Q. robur) has been grown throughout the San Francisco Bay Area, with old examples scattered around. This photo is a tree growing in Palo Alto. It was discovered by volunteers of the non-profit Canopy, as they surveyed the native oak trees of the Palo Alto. When approached, the owner described collecting the acorn from which this tree grew at Golden Gate Park in San Francisco, where several groves of English Oak can be found, growing close to playgrounds. The owner also admitting his regret in planting the tree over his patio. Unfortunately, English Oak is highly vulnerable to aphids, at least in the Bay Area, and the trees consistently display leaves coated in sooty mold in the summer, along with copious aphid exudate, leaving the ground beneath sticky.