The tree is on the property line. Who owns it, and who decides what happens to it?

What is actually happening

Trees planted near a fence decades ago have grown over it. A trunk that was a foot inside one lot at planting is now 30 inches across and straddles whatever line exists. Meanwhile, the fence itself may never have been on the line. The arguments that follow ("it's my tree," "it's your tree," "it's on the fence so it's half mine") are usually all wrong in the same way: nobody has measured.

The arborist's measurement is at ground level where the trunk meets the soil, not at the canopy and not at chest height. A trunk that leans can appear to be on one side at eye level and stand on the other at the ground.

What California law says

• Civil Code 833. Trunk wholly on one lot: that owner's tree, whatever the roots and branches do.
• Civil Code 834. Trunk standing partly on the land of two or more adjoining owners: the tree belongs to them in common.
• What co-ownership means. Neither owner may remove the tree or injure it without the other's consent; a co-owner who does is liable to the other (Civil Code 3346 applies, with its double and treble damages). Each may trim overhang on their own side within the Booska v. Patel limit. Costs of maintenance are shared by agreement; the code sets no formula.
• The line. Only a licensed land surveyor determines the boundary. Fences, hedges and old understandings do not. If the parties cannot agree where the trunk stands relative to the line, a survey comes before anything else.

What your city adds

A boundary tree above the city's size threshold needs a removal permit like any other, and the application generally requires the consent of both owners. Some cities will not accept an application for a shared tree from one owner at all. If the tree is hazardous, the hazard permit path applies and the report supports it. Permit rules by city →

What the report does for you

1. Measures and photographs the trunk at ground level against the fence line and any survey monuments, and states plainly whether it appears wholly on one lot, straddling, or too close to call without a survey.
2. Assesses species, size, condition and risk, so both owners know what they jointly own and whether it needs work.
3. Writes a maintenance or pruning specification both owners can sign, with a suggested cost split.
4. If removal is on the table, states whether a permit would issue and what both owners must sign.
5. Cites 833, 834, 3346 and the city's ordinance, and names the surveyor hand-off where it is needed.

Dispute Assessment Report, from $850. Jointly commissioned by both owners whenever possible; both sign and both receive it. Pricing →

What to do this week

1. Do not cut, remove or heavily prune anything. On a shared tree, that is the one move that converts a disagreement into a damages claim.
2. Find your title documents and any survey from purchase; monuments may be noted.
3. Propose a joint report to the neighbor. One neutral document both paid for is the usual way out.
4. Start a report or text (415) 881-0124.

Sources

1. Civil Code § 833, § 834, § 3346.
2. Booska v. Patel (1994) 24 Cal.App.4th 1786.