The basic rule
Anyone wishing to fell a tree on their property in Gatineau must obtain an authorization certificate, and the certificate has to be obtained before the work begins. The City states it that way on its own page, and adds that a breach of the by-law carries a fine.
The by-law applies to trees 10 cm or more in diameter measured 1.3 m above the ground. That is a low threshold: a tree planted when a 2000s house was built has often passed it already. To check without instruments, measure the trunk circumference at chest height with a tape and divide by 3.14.
The application is made online or by calling the City's non-emergency line at 311. Processing time belongs in your schedule, and a contractor who suggests cutting first and sorting the paperwork afterwards is exposing you to the fine rather than himself.
The reasons the City accepts
The certificate is not automatic. The regulation lists the situations that justify removal, and they concern either the condition of the tree or a real conflict with a use of the land.
On condition: a dead tree, a tree with an incurable disease, a tree infested by insects threatening its survival, and a dangerous tree. On conflict: a tree causing damage to the property, a tree creating an unreasonable nuisance, a tree hindering the growth of neighbouring trees of greater value, a tree within 1 m of the foundation of an existing building, a tree interfering with a structure or construction according to the prescribed distances, and a tree interfering with the installation or maintenance of a septic system.
What is absent from the list is instructive too: leaves in the gutter, shade on the vegetable garden and a wish for more parking are not grounds. If your situation fits none of the boxes, maintenance is the road that remains, and it is often the right one anyway.
The replacement tree
A felled tree must be replaced in two cases: if the lot no longer meets the minimum tree requirements set by the zoning by-law, and if the removal makes room for construction such as an accessory building, a pool or a fence.
The City sets the size of the replacement: at least 2.5 m for a broadleaf and at least 1.5 m for a conifer. That is not a small nursery plant, and the cost of the tree, the planting and the first year's watering belongs in the project budget.
Two further rules govern where it goes. Planting a tree on municipal land, meaning in the street right-of-way, is expressly prohibited. And a planted tree has to sit more than 1.5 m from the street paving, the sidewalk or the curb. A replacement tree planted too close to the sidewalk is a second problem rather than a solution.
What is prohibited in pruning
Pruning does not require a certificate, but it is regulated. Removing more than half of a tree's living branches is prohibited. Topping a tree is prohibited. Pruning must not shorten the tree's life or cause its death, the natural silhouette has to be preserved, and the work must meet the standards of the Bureau de normalisation du Québec.
The prohibition on topping matters most in practice, because topping is still sold under reassuring names such as cutting back or taking the top off for safety. A topped tree produces many sprouts, poorly anchored to the cut wood, and ten years later carries a crown heavier and weaker than before the work was done.
Trees in the street right-of-way belong to the City and must not be cut or pruned by a property owner. For a municipal tree the call goes to 311. For a branch approaching a power line, the call goes to Hydro-Québec before anyone else.