Tigard, OR Invasive Plant Rules: Prohibited Species (2026)

The list sits in paragraph 8 of the "noxious vegetation" definition in § 6.01.020 of the Tigard Municipal Code: Hedera helix L. (English ivy), Heracleum mantegazzianum (giant hogweed), Lythrum salicaria L. (purple loosestrife), Polygonum cuspidatum (Japanese knotweed) and Rubus discolor (Himalayan blackberry). Section 6.02.020.C prohibits planting those plants, or allowing them to be planted, on the property, and § 6.02.020.D requires the responsible party for a violation to remove or otherwise destroy them. "Responsible party" under § 6.01.020 is broader than the deed holder: it covers an owner, an agent with authority over the property or responsibility for its maintenance, any person occupying the property including a tenant, the person who created or allowed the condition, and a foreclosure or bankruptcy trustee.

More than one party can be responsible for the same property. Other paragraphs of the same definition reach additional plants. Blackberry bushes that extend into a right-of-way or across a property line are covered by paragraph 5, and poison oak, poison ivy or similar vegetation by paragraph 3. Those are governed by § 6.02.020.A and B, which bar allowing them on the property or in the abutting right-of-way and require cutting down or destroying them. The definition excludes vegetation that constitutes an agricultural crop unless it is a health hazard, a fire hazard or a traffic hazard. Enforcement runs through Chapter 1.16 of the code, which the City of Tigard uses for every nuisance violation.