Local tree-rule guide
St. Thomas tree rules
St. Thomas protects large private trees through By-law 101-2021, including live and dead trees over 30 cm DBH, and uses separate rules for municipal trees and woodlands.
The local rule
St. Thomas’s Private Tree Preservation By-law makes it an offence to destroy or injure a private tree with a DBH greater than 30 cm without a permit.
The by-law also requires a permit for felling a dead tree over 30 cm DBH rather than treating dead status as an automatic exemption.
Deforestation in a woodlot or woodland is separately regulated under the same private-tree framework.
Municipal trees have their own by-law, so confirm ownership before applying the private-tree rule to a trunk near the street.
Local exceptions and conditions
The 30 cm private-tree trigger
- By-law 101-2021 regulates destruction and injury of private trees with a DBH greater than 30 cm.
- Measure DBH consistently and keep a photo of the tape position if the tree is near the threshold; a small measuring difference should not be left to argument after work starts.
- The permit requirement is not limited to healthy trees. The by-law’s set-fine schedule separately identifies felling a dead tree over 30 cm without a permit.
- Because tree status, woodlots and municipal ownership create additional branches, confirm the permit category rather than relying only on the number.
- The operative clause says “more than 30 cm” DBH, measured at 1.37 m above ground. Exactly 30.0 cm is outside that specific size clause, although other protected-tree, replacement, woodland or municipal-ownership rules can still apply.
Dead trees still need the permit path
- A dead-tree diagnosis does not erase the St. Thomas permit requirement when the trunk is over the private-tree threshold.
- If the tree is hazardous, document the hazard and ask the City how urgent work should be handled before removal where time allows.
- An arborist assessment can help establish condition and risk, but the professional diagnosis is evidence for the permit—it is not itself municipal authorization.
- Keep the permit available on site because the by-law also requires compliance with permit terms and posting requirements.
Woodlots and deforestation
- The by-law separately addresses deforestation in woodlots or woodlands, so a multi-tree clearing project should not be reduced to a series of single-tree measurements.
- If the property contains a wooded block, identify whether it meets the by-law’s woodland definitions before clearing access, grading or harvesting.
- Development and natural-heritage approvals can add further conditions on a wooded site beyond the private-tree permit itself.
- For a project site, coordinate the tree permit with the planning/building file so protection zones and removals are consistent across approvals.
Municipal trees and enforcement
- St. Thomas also maintains a Municipal Tree Preservation By-law for trees under City control.
- A tree close to the road should be checked for municipal ownership before a homeowner or contractor prunes roots, removes branches or takes down the tree.
- The private-tree set-fine schedule shows substantial penalties for unpermitted destruction, injury and dead-tree felling over the threshold, so guessing is a poor substitute for a permit check.
- The checker remains conservative for St. Thomas because even a clear private-tree size trigger does not answer public ownership, woodlot or special-site conditions by itself.
Before work starts
- Ownership: confirm whether the trunk is private, shared or on public land before authorizing work.
- Site context: check development approvals, environmental controls, easements and any prior tree-retention conditions that apply to this property.
- Work requirements: obtain the current permit, certificate, exemption or written municipal confirmation before the contractor starts.
- Keep the record: retain photos, measurements, professional reports and the municipal decision with the property file.
Official sources
Private Tree Preservation By-law 101-2021 (PDF)Official source ↗St. Thomas by-law directoryOfficial source ↗By-law 101-2021 — set fine schedule (supporting enforcement source)Official source ↗St. Thomas road permits — tree protection noteOfficial source ↗
Last verified: October 7, 2026. Rules, maps and application procedures can change; confirm with the local authority before work. How we research