Sonoma County, CA Landscaping Rules: Tree Removal & Heritage Trees (2026)

Sonoma County's tree protection framework is concentrated in Chapter 26 (Zoning Regulations) and Chapter 26D (Heritage and Landmark Trees). The Tree Protection Ordinance at Code §26-88-010(m) requires a zoning permit and mitigation (replanting, preservation, or in-lieu fees) to remove protected native species measuring 6 inches in diameter or greater at breast height (4.5 ft above grade). Protected species include native oaks (valley oak, coast live oak, blue oak, black oak), maples, cottonwoods, alders, willows, redwoods, and listed pines and cypress. Larger specimens — 36 inches diameter or more for hardwoods, 48 inches for redwoods — require a use permit rather than the minor zoning permit. Chapter 26D (Heritage and Landmark Trees) makes it unlawful to remove any tree formally designated as a heritage or landmark tree without first obtaining a tree permit. The Oak Woodland Ordinance (§26-67) regulates removal and development inside the OAK Combining Zone, permitting one-time oak woodland conversion of up to a half-acre per parcel but otherwise requiring a use permit for larger projects. Trees inside the Riparian Corridor (§26-65) face additional protections. On April 16, 2024, the Board of Supervisors adopted a comprehensive update that expanded protected native species coverage, lowered the size threshold for protection, and provided exemptions for public safety, defensible space, and ordinary residential maintenance. In-lieu mitigation fees are calculated at $510 per arboreal value point, which scales with diameter and species. Sudden Oak Death (caused by Phytophthora ramorum) is endemic to Sonoma County, and oak removals may also need to follow state Sudden Oak Death management protocols and the California Department of Food & Agriculture quarantine rules for moving infected wood.