Your Neighbour’s Tree — What You Can and Can’t Cut.

Everything depends on the trunk

Ownership of a tree in Ontario follows the trunk, not the canopy and not the roots. A tree whose trunk stands entirely on your neighbour’s land is their tree, even when half of it hangs over your yard. A tree whose trunk crosses the property line at any point belongs to both of you.

That second category has teeth. Section 10 of Ontario’s Forestry Act makes a boundary tree the common property of both owners, and injuring or destroying one without the consent of every owner is an offence. Ontario courts have applied it strictly: in Hartley v. Cunningham the court stopped one owner from felling a healthy boundary tree despite the other owner objecting only to the loss of the tree.

Before any argument starts, take a tape measure to the base and look at where the trunk actually meets the ground. Plenty of disputes on North York streets have ended there, with both parties surprised.

Branches hanging over your property

Where the trunk is clearly on your neighbour’s side, the traditional common law position lets you trim growth that crosses the boundary, back to the property line and no further. You cannot reach across to cut, you cannot enter their land without permission, and you cannot take so much that you damage or destabilise the tree.

Cut branches technically remain your neighbour’s property, so throwing them back over the fence is a poor idea for reasons beyond neighbourhood relations. Ask first, and put the request in writing if the relationship is already strained.

Toronto adds a layer the common law does not. If that tree is 30 cm or more across the trunk, it is protected under Municipal Code Chapter 813, and heavy cutting counts as injuring it whichever side of the fence you stand on. The fine range is $500 to $100,000 per tree.

Roots, patios and drains

Roots follow the same principle as branches, with the same limit: you may deal with what crosses onto your land, and you may not destabilise the tree. That limit matters more with roots than branches, because cutting a major root within a few metres of the trunk can take out a large share of the tree’s anchorage on that side.

Roots lifting a patio slab or a walkway usually have cheaper answers than cutting. A root barrier installed along the boundary, a re-laid slab over a bed of clear stone, or a section of path rebuilt as a floating deck all solve the problem without putting the tree over.

Roots in a drain are a different diagnosis. Roots do not break sound pipe. They find joints and cracks that are already leaking, then fill the space, so the cracked pipe is the problem and the root is the symptom.

When a neighbour’s tree falls into your yard

Where a healthy tree comes down in a storm, insurers generally treat it as an act of nature, and each owner claims for the damage on their own property under their own policy. Nobody is negligent for failing to predict a windstorm.

Negligence changes the picture. If the tree was dead, visibly failing, or the owner had been told in writing that it was hazardous and did nothing, the conversation moves from insurance to liability. This is the entire practical reason to get a written assessment on a suspect tree and send a copy to the neighbour, before it fails rather than after.

Keep the paper. A dated arborist report, a photograph of a split union, and a note of the date you raised it are worth more than any argument at the fence line.

City trees and boulevard trees

The tree between the sidewalk and the road is the City’s, regardless of who waters it. City-owned trees are protected at any size under Chapter 813, and pruning, cutting roots or removing one is Urban Forestry’s call. Requests go through 311.

The same applies to a tree standing on parkland behind your fence, and to anything inside a ravine boundary under Chapter 658. Trimming an overhanging branch off a City tree yourself is the sort of small decision that produces a large invoice.