Understanding Boundary Line Trees
A boundary line tree is defined under Washington law as “a tree standing directly upon the line between adjoining owners, so that the line passes through it, is the common property of both parties, whether marked or not.’” Herring v. Pelayo, 198 Wn. App. 828, 836, 397 P.3d 125 (2017) (quoting Happy Bunch LLC v. Grandview N. LLC, 142 Wn. App. 81, 93, 173 P.3d 959 (2007). These trees are common property, meaning both neighbors share ownership and responsibilities.
Unlike trees entirely on one property, boundary trees cannot be treated as encroachments. Each owner has rights to use and maintain the tree—but not to destroy it. Cutting or killing a boundary tree without consent can lead to serious legal consequences.
Legal Risks: Timber Trespass and Treble Damages
Under RCW 64.12.030, anyone who injures or destroys a tree without lawful authority may owe three times the actual damages. Courts apply this statute to boundary trees because both owners have an undivided interest. Even trimming that knowingly kills the tree can trigger liability.
Case law (Herring v. Pelayo, 198 Wn. App. 828 (2017)) confirms that while owners may trim overhanging branches, they cannot act in a way that kills the tree. Violating this duty can result in treble damages and costly litigation.
Seattle Municipal Code Updates (2023–2025)
Seattle strengthened its tree protection laws through Ordinance 126821, which went into effect on July 30, 2023. Key updates include:
- Tiered Tree Classification: Heritage and significant trees now fall under Tier 1 and Tier 2 protections.
- Permit Requirements: Removing or altering Tier 1 or Tier 2 trees requires a permit from SDCI.
- Mitigation Fees: Removal of protected trees triggers fees based on size and species.
- Environmentally Critical Areas: Extra restrictions apply to trees on steep slopes, wetlands, and shorelines under SMC 25.09 and 25.11.
- Street Trees: Cutting roots or trenching near street trees requires SDOT Urban Forestry approval (SMC 15.43).
Additional Highlights from Seattle’s Tree Protection Ordinance:
- Protects approximately 157,000 additional trees, including those on non-redevelopment sites.
- Requires replacement for any tree removed that is 12” or greater in diameter, including hazardous trees.
- Tier 1: Heritage trees must be retained unless hazardous.
- Tier 2: Formerly “exceptional” trees now protected at 24” diameter (previously 30”).
- Replacement options include replanting onsite or paying into the One Seattle Tree Fund.
- Increased fines for illegal tree removal and penalties for unregistered tree service providers.
- Seattle aims for 30% canopy cover by 2037, guided by the Tree Canopy Equity and Resilience Plan.
These changes mean property owners must check local codes before trimming or removing any tree, especially near property lines.
Practical Tips for Property Owners
- Confirm the Boundary: Review surveys and title history before acting.
- Get Written Consent: If the tree is on the boundary, secure your neighbor’s agreement.
- Check Seattle Tree Laws: Permits and mitigation fees may apply.
- Avoid Self-Help: Trimming that kills a boundary tree can lead to treble damages.
- Consult a Real Estate Attorney: These disputes are fact-intensive and often emotional.
Why This Matters
Boundary tree disputes can escalate quickly, leading to lawsuits, damaged relationships, and significant financial exposure. Understanding your rights—and your duties—under Washington law and Seattle’s municipal codes is essential.
Need Help with a Boundary Tree Dispute?
At Holmquist & Gardiner PLLC, we help property owners navigate complex tree and boundary issues. Contact us today for a consultation and protect your property rights.
