Around Pomona, CA, several cities protect native oaks, walnuts and other large trees even on private property. Walnut covers oaks and walnuts as small as 6 inches in circumference. Diamond Bar protects native oak, walnut, sycamore and willow 8 inches DBH and up on lots over half an acre. San Dimas covers oaks 8 inches and up and other trees 10 inches and up. La Verne protects all oaks and significant trees. Covina protects oaks 10 inches and up as heritage trees. Chino Hills protects native sycamore, oak, walnut and scrub oak 4 inches and up in certain situations. Always check with the city before cutting.
City by city
- [Walnut](/service-areas/walnut/). Oak and walnut trees 6 inches or more in circumference at 4.5 feet need a City tree permit for cutting, pruning, removal or work in the protected zone. See the Walnut ordinance.
- [Diamond Bar](/service-areas/diamond-bar/). Native oak, walnut, sycamore and willow 8 inches DBH and up are protected. Removal needs a permit, and pruning branches over 4 inches needs a pruning permit. Lots of half an acre or less are exempt for these natives.
- [San Dimas](/service-areas/san-dimas/). Mature significant trees: oaks 8 inches and up, other trees 10 inches and up, multi-trunk 38 inches total circumference, measured 36 inches above grade.
- [La Verne](/service-areas/la-verne/). All oaks and significant trees need a removal permit. Pruning significant trees needs a no-fee permit.
- [Covina](/service-areas/covina/). Oaks 10 inches DBH and up, or 22 inches combined for multi-trunk, are heritage trees and need a tree preservation permit. See the Covina ordinance.
- [Chino Hills](/service-areas/chino-hills/). Native sycamore, coast live oak, black walnut and scrub oak 4 inches and up need a permit on undeveloped land, or on developed land in the Fire Hazard Overlay when visible from streets, parks or trails.
How to measure your tree
Most rules measure trunk diameter at breast height, about 4.5 feet above the ground. San Dimas measures at 36 inches. Walnut uses circumference. To get diameter, measure the circumference with a tape and divide by about 3.14.
What counts as damage
Many ordinances cover more than removal. Pruning, root cutting, trenching, paving and grade changes inside the dripline can all count. Plan construction and landscaping around protected trees carefully.
Why native trees are protected
Oaks, walnuts and sycamores support wildlife, hold soil on slopes and take a very long time to replace. Many were here before the neighborhoods.
Caring for native oaks
- Keep summer irrigation away from the trunk.
- Avoid soil changes inside the dripline.
- Prune lightly in cooler months.
- Never top an oak.
A tree health assessment helps if an oak looks stressed.
Pomona itself
Pomona's main tree rules focus on street trees and historic districts. See our guides on street trees and historic district tree work.
Before you call a tree service
Know your city, measure the trunk if you can and take photos. That helps us tell you quickly whether a permit is likely. Call (909) 479-2666.
Emergencies and storm damage
Most ordinances have an emergency exception for a protected tree that is an immediate danger after a storm. Make the area safe, document the damage with photos before and after and contact the city as soon as you can. Do not use an emergency as a reason to remove more than is needed.
Planning a project near a protected tree
If you are planning an addition, ADU, pool or new driveway, mark the dripline of every protected tree on the plan first. Work inside the dripline can count as damage under several of these ordinances. Talking to the city at the design stage is far easier than fixing a problem later.
Need work on a protected tree? See tree trimming and tree removal.
Common questions
Which nearby city has the strictest oak rules?
Walnut's ordinance is among the broadest, covering oak and walnut trees as small as 6 inches in circumference and requiring a permit for pruning as well as removal. Diamond Bar, San Dimas, La Verne, Covina and Chino Hills each have their own thresholds and exemptions, so check the specific city.
Does pruning count under these ordinances?
In several cities, yes. Walnut requires a permit for pruning protected trees. Diamond Bar requires a pruning permit for branches over 4 inches at the cut. La Verne requires a no-fee permit for pruning significant trees. Covina exempts light routine maintenance within set limits.