Los Altos Heritage Trees & the 12-Inch Rule

I consult on tree projects in Los Altos regularly, and the most expensive mistake I see is homeowners who assume their tree is too small to be protected. In Los Altos, the threshold is lower than most Peninsula cities — and for native species, it is lower still.

The 12-Inch Baseline

Under Los Altos Municipal Code Chapter 11.08, the most common trigger for a Tree Removal Permit is size. Any tree with a trunk diameter of 12 inches or greater, measured at 48 inches above the ground (standard DBH), is considered a Protected Tree — regardless of species.

If you are measuring with a tape, that equates to a circumference of roughly 38 inches. Wrap the tape around the trunk at chest height. If it reads 38 inches or more, you are looking at a protected tree.

This threshold is stricter than several neighboring cities. Palo Alto starts at 15 inches for non-native, non-oak species. Compare all 25 City thresholds using our ordinance comparison tool.

Native Species: The 10-Inch Rule

Los Altos places extra value on biodiversity. Because native trees are better adapted to the local ecosystem and provide superior drought resilience, they are protected at a smaller size. A permit is required to remove any of the following species at 10 inches or greater in diameter:

Oaks: Coast Live Oak (Quercus agrifolia), Valley Oak (Quercus lobata)

Redwoods: Coast Redwood (Sequoia sempervirens)

Others: California Buckeye, Western Sycamore, and Bigleaf Maple

The two-inch difference between the native threshold (10 inches) and the general threshold (12 inches) catches more trees than you might expect. A 10-inch oak is not a small tree, but it is common in Los Altos yards — and many homeowners do not realize it is protected.

What Is a Heritage Tree in Los Altos?

The term "heritage tree" gets used loosely in conversation to mean any old or large tree. In Los Altos, it is a specific legal designation. A Heritage Tree is any tree that has been officially designated by the Historical Commission for its age, rarity, size, or historical significance to the city.

The city maintains an official Heritage Tree Record through the City Clerk's Office. Unlike the 12-inch rule, a Heritage Tree is protected at any size once designated. You cannot remove, significantly prune, or damage a Heritage Tree without specific approval from the city.

Heritage Tree status is sometimes attached to a property's history. If you recently purchased a home in Los Altos, it is worth checking whether any trees on the lot carry this designation — your real estate agent may not have flagged it, but the city has it on file.

The Cost of Non-Compliance

Los Altos enforces its tree protections aggressively. Removing a protected or Heritage tree without a permit can trigger:

Civil penalties: Fines that can reach several thousand dollars per violation. The exact amount depends on the tree's appraised value and the circumstances of the removal.

Mitigation planting: The city can require you to plant multiple replacement trees for every one removed illegally. I have seen requirements of up to five 48-inch box trees per violation — at $1,500–$3,000 per tree including installation, that adds up fast.

Stop-work orders: If a tree is removed during a construction project without a permit, the city can halt all on-site work immediately. This often lasts weeks while "restitution planning" is completed. For a contractor billing daily overhead, every day of delay costs the homeowner money.

See our penalty calculator for estimated fines across All 25 Bay Area cities.

The Professional Path

Before any tree work in Los Altos — removal, major pruning, or root cutting during construction — your first step should be an arborist assessment. A certified arborist will measure the DBH, identify the species, and check the city's Heritage list to confirm whether your tree is protected and what permits you need.

This applies to construction projects too. If you are planning an ADU or remodel, get a tree inventory before the architects finalize the site plan. Moving a building footprint 10 feet is cheap. Paying $30,000+ in tree violation penalties is not.

How Los Altos Compares to Neighboring Cities

Every Peninsula city draws the line differently on tree protection. If you own property near a city border — or are comparing cities for a home purchase — here is how the thresholds stack up:

Notice the key detail with Palo Alto: they measure at 54 inches above grade rather than the standard 48 inches. That non-standard measurement catches people off guard — a tree that measures 14.5 inches at 48 inches might measure 15 inches at 54 inches and trigger Palo Alto's threshold. See our Palo Alto dead tree permit guide for the full breakdown.

Real Scenarios I See in Los Altos

The ADU surprise. A homeowner on El Monte Avenue was halfway through ADU permitting when the city flagged a 14-inch Coast Live Oak within the construction envelope. They had not included a tree report in their plans. The stop-work delay cost them six weeks and $4,500 in arborist reports and revised engineering. A pre-construction tree inventory — which would have cost $500 — would have caught it before the first permit application.

The "it is just an oak" miscalculation. A client on University Avenue assumed their backyard oak was too small to worry about. It measured 11 inches at breast height — one inch over the native species threshold. Because they had a landscaper start pruning without a permit, the city cited them for unauthorized work on a protected tree. The penalty included two replacement plantings and a fine. One inch made the difference.

The Heritage Tree discovery. A couple who bought a home on Fremont Avenue in 2024 had no idea the large deodar cedar in their front yard was on the Heritage Tree Record. They learned about it when they applied for a driveway expansion. The Heritage designation did not stop the project, but it required a certified arborist report, root protection plan, and city approval — adding $2,000 and eight weeks to the timeline. Checking the Heritage list before buying would have set expectations.

Next steps: Use our Permit Checker to see if your tree qualifies as protected, review our full Los Altos permit guide, or read the Bay Area Heritage Trees overview for how Los Altos compares to neighboring cities.