Yes – and in Atherton it is more than bad horticulture: the town’s own code lists excessive watering of oak trees as prohibited damage to a heritage tree. Native oaks evolved for bone-dry California summers. Years of irrigation around the root crown creates the warm, wet conditions in which root-rot organisms thrive, and the tree declines slowly until a limb or the trunk fails.

What protects an oak in a landscaped setting: keep irrigation and plantings outside the root crown area (ideally several feet from the trunk and light within the dripline), use mulch instead of turf under the canopy, and avoid trenching through the root zone. If your oak already stands in a lawn, an assessment now beats a structural surprise later – decline is treatable early and irreversible late.