Most boundary tree disagreements never reach a courtroom. The three that did, and produced a written decision worth knowing about, each turned on a specific fact a homeowner could have documented in advance: where a trunk actually sits, how bad a tree’s condition really is, and what damaging one costs when it wasn’t yours to touch.
This is a summary of published decisions, not legal advice, and none of it will tell you what your own dispute is worth. For the statute and common-law framework these cases sit inside, see our guide to neighbour tree disputes in Ontario.
Hartley v Cunningham: A Trunk Can Cross the Line Above Grade
Ontario’s Forestry Act (R.S.O. 1990, c. F.26) makes a boundary tree the common property of both owners under section 10(2), where the trunk grows on the property line itself. Section 10(3) makes it an offence to injure or destroy that tree without both owners’ consent. Hartley v Cunningham settled a question the statute leaves open: what counts as the trunk.
The court read the word broadly, covering the whole stem from the roots up to where it branches into limbs and foliage, rather than only the point where it meets the ground, and the Ontario Court of Appeal upheld that reading in 2013 (2013 ONCA 759). A tree with a base sitting entirely on one owner’s side can still be common property if the trunk leans or forks across the line higher up.
That distinction has teeth. Section 19(1) sets the penalty for injuring or destroying a boundary tree without consent at a fine of up to $20,000, imprisonment for up to three months, or both. Deciding a tree is “clearly” on one side based on where it enters the soil, without checking where the trunk sits further up, is the kind of assumption Hartley v Cunningham shows a court will not accept.
Freedman v Cooper: A Documented Hazard Beats a Refusal to Consent
The Forestry Act’s consent requirement assumes both owners agree before a boundary tree comes down. Freedman v Cooper tested what happens when one owner refuses and the tree is genuinely dangerous: a boundary Norway maple lost a third of its canopy in an ice storm, two separate arborists reported a continuing risk, and one co-owner still would not consent to removal.
The Ontario Superior Court held in 2015 that nuisance law, not the Forestry Act’s consent requirement, governs a hazardous tree, and ordered the objecting owner not to interfere with removal (2015 ONSC 1373). The consent requirement did not disappear; it was displaced by a different legal test once the hazard was proven.
What made that outcome available was the paper trail, not the argument. It took condition reports from more than one arborist to establish the risk, and a court application to enforce it. A neighbour’s opinion that a tree looks unsafe does not carry the same weight as a written risk finding. A TRAQ-based tree risk assessment is the kind of document a court is likely to weigh in a dispute built on this precedent.
Murphy v Mullen: What Damaging a Tree Costs
Murphy v Mullen is not a boundary-tree ownership case. It answers a different question: what a court awards once a tree has already been damaged. The Ontario Court of Appeal’s 2021 decision put the number in six figures once replacement, restoration, and lost screening value were counted (2021 ONCA 872).
The common-law self-help right to prune back an overhanging branch or root has two hard limits: no stepping onto the neighbour’s property to do the cutting, and no cutting that kills the tree or leaves it structurally unstable. Murphy v Mullen is what waits on the other side of that second limit. A dispute over a few overhanging branches is a pruning question with a defined boundary. Removing or seriously injuring a tree that turns out not to be entirely yours, whether it’s a true boundary tree under the Forestry Act or simply growing on the other side of the line, is exposure of a different order, and this is the case that shows what it can add up to.
Documentation Is What Moves These Cases
In each case, the outcome turned on a record that existed before anyone filed anything: where a trunk actually sat, what an independent arborist found on inspection, what a tree looked like before it was cut. A condition assessment before a dispute starts, a risk report from an independent arborist, dated photographs of a trunk’s position relative to a fence line: that’s the record a lawyer asks for, and the one these cases show actually decides a result.
The same logic applies before a shovel goes in the ground. A tree protection zone is measured outward from the trunk, not from the property line. If that zone overlaps a construction disturbance area across the fence, the tree belongs in the project’s protection plan, a scope question our guide to trees you don’t own covers in more detail. A construction arborist report maps that before a design is finalized rather than after equipment shows up.
If a neighbour has already sent a letter through counsel, or a tree has caused real property damage, a lawyer settles the dispute, not a blog post. What an independent arborist can do first is give that lawyer, or the neighbour across the fence, something more solid than two conflicting opinions about the same tree.