Text Size:   A+ A- A   •   Text Only
Site Image
Noxious Weed Listing Process
Policy for Listing Noxious Weeds
The Oregon State Weed Board (OSWB) updates the State Noxious Weed List annually. Changes can include adding new species, change of classification of a previously listed species (A, B, or T), or delisting species that has become low priority. The Noxious Weed Control Program provides technical assistance to the OSWB by developing plant risk assessments. A written risk assessment process is used to identify what species are of high risk and should be listed. The ODA risk assessment is a series of questions that evaluates current geographic distribution, plant biology, resources impacts, and difficulty of detection and control. Risk assessments are scored using the best available information, observations, and literature reviews.

Noxious Weed Listing Procedure: 
  • Plant species are submitted for review. Anyone can request ODA to evaluate a species for listing.
  • An internal review process is conducted to determine if a plant warrants additional evaluation.
  • Plants of high concern, causing documented impacts, are placed on the Watch List for further review and background information gathering.
  • Formal written risk assessments are prepared.
  • Plants that score high on the risk assessment are presented to the OSWB for listing. Species that score low or are not listed by OSWB but kept on file for future reference or may be returned back to the Watch List.
  • Statewide management plans are developed for A and T listed weeds. Plans for B listed weeds are determined on a case-by-case basis based on regional priorities and biological control targets.
  •  New listed weeds are added to the State Noxious Weed Quarantine (OAR 603-52-1200). 

Listing Process Diagram

Risk Assessments (Downloadable PDFs)
African rue
Barbed & ovate goatgrass

Distaff thistle
European water chestnut
Flowering rush
Giant hogweed
Meadow hawkweed
King devil hawkweed
Yellow devil hawkweed
Mouse ear hawkweed
Oblong spurge
Orange hawkweed
Paterson curse
Pheasant eye
Purple nutsedge
Spanish heath
Squarrose knapweed
Tree of heaven
Yellow arch angel
Yellow floating heart