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Phone: 503-823-7740

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1120 SW 5th Avenue, Room 1000, Portland, OR 97204

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Frequently Asked Questions

Invasive Plant Policy Review
and Regulatory Improvement Project

Frequently Asked Questions

1. What is the Invasive Plant Policy Review and Regulatory Improvement Project?

The Invasive Plant Policy Review and Regulatory Improvement Project is a project to implement certain recommendations in the City of Portland’s Invasive Plant Management Strategy. The Bureau of Environmental Services (BES) is funding the Bureau of Planning and Sustainability (BPS) to lead an evaluation of City policies and rules relating to invasive plants, and to make recommendations for potential updates and improvements.

2. Why does the City of Portland have a Nuisance Plants List? Why not use the Oregon Department of Agriculture (ODA) noxious weed list?

The City of Portland developed the native, nuisance, and prohibited plant lists in 1991 and published them as the Portland Plant List. These lists have been modified several times since then to reflect new scientific information about plants. The lists guide natural area management in the Portland area by defining which species are native and invasive in the Portland area, and which species are invasive in natural area settings. Plants that are invasive in natural areas are also usually invasive in urban area settings. The Portland Plant List is specific to plant species that grow in the Portland metropolitan area.


In contrast, the Oregon Department of Agriculture (ODA) noxious weed list has been developed for the entire state. It includes both agricultural and ecological weeds, also known as invasive plants. Approximately half of the species on the ODA list are not known to occur in the Portland area. Therefore, a more localized list was developed to identify the plants that threaten the health and safety of the Portland metropolitan area citizens and natural areas. Of particular note, the ODA list typically has a more agricultural land management focus rather than urban and natural areas management.

3. Will this list prevent nurseries from selling certain plants on the Nuisance Plants List? Will this change which species can be commercially grown or produced?

Nursery sales are regulated by the Oregon Department of Agriculture under administrative rule (OAR 603-052-1200). This rule prohibits import, transport, propagation or sale of select "A" and "B" State listed noxious weeds and plants on the Federal Noxious Weed List (7 C.F.R. 360.200). The City of Portland does not have jurisdiction to regulate nursery sales or agricultural commodities in Oregon.


The City’s Nuisance Plants List includes some of the plants on the ODA noxious weed list; those plants would remain subject to OAR 603. The City of Portland has made managing invasive plants a priority; however, the City of Portland does not limit the sales of certain plants. Instead, the City focuses efforts on education and outreach, and working with the nursery and seed industry, as well as with ODA.

4. Does the Portland Plant List include all native and non-native plants?

No, the Portland Plant List defines a list of native and of nuisance species for the Portland metropolitan area. There are lots of plants that are not native and not invasive. Examples include many landscape ornamental plants and food crops. Landscape ornamentals such as winter daphne (Daphne odora), cosmos (Cosmos pinnatus), and lilacs (Syringa spp.) are popular non-native plants that are not known to escape into natural areas. Similarly, carrots, cucumbers, lettuce and most other food crops do not spread beyond gardens into natural areas because they need irrigation to persist through our dry summers. GardenSmart Oregon: A Guide to Non-Invasive Plants is a great guide to help people select non-invasive plants. It is available online at

5. How was the Nuisance Plants List developed? In other words, how did you decide what is invasive and which species should be included on the Nuisance Plants List? Did you complete formal risk assessments?

This version of the Nuisance Plants List is an update of the existing list which has 163 plants. As proposed, 43 species will be added to the list and 23 species will be removed from the list. These changes were made based upon feedback from internal and external stakeholders that consist of botanists, horticulturalists, plant ecologists, and natural areas land managers. Field knowledge and expertise from the stakeholders, and resources such as databases and reference materials were used to determine which species should remain, or be added to the list, and to assign priority ranks (“A-D”, “W”).


Plants defined as invasive are known to spread rapidly and can form monocultures in natural areas. In many cases, these species alter natural successional patterns and permanently alter habitat conditions. It is easy to transport plants between urban areas, agricultural areas, and natural areas. Plants can be purchased at stores and installed in yards. Vehicles can track plant seeds on tires. Humans can track seeds on their shoes, and livestock and pets can transport seed on their fur or feet. Many seeds and other plant parts are dispersed by wind and water. Animals may eat seeds and deposit them.


Due to the number of species on this existing list, the City determined it does not have the resources to conduct a risk assessment for all of the species on the list. However, as part of the stakeholder review process, the City offered to complete risk assessments for any species where there is disagreement about the proposed ranking.

6. Why were native species removed from the Nuisance Plants List?

To avoid confusion about native and invasive plants, native species have been removed from this version of the Nuisance Plants List. This is consistent with state noxious weed lists in Oregon and Washington which do not include native species. The Portland Plant List previously included native species on the Nuisance Plant List because some of them have human health impacts, for example, poison oak causes a skin rash. In addition, some native species grow more quickly than others and/or they have hybridized with non-native cultivars making them grow more aggressively. However, since most state noxious weed lists include only non-native invasive species, the City of Portland Nuisance Plants List now also only includes non-native invasive species.

7. Why were the Nuisance Plant List and the Prohibited Plant List combined?

The two lists were combined because the City’s regulations apply to the nuisance and prohibited plants in the same manner. In addition, the City proposes to add priority ranks (“A-D”, “W”) for each of the plants. Combining the list and formatting it in an order using the ranks, and in alphabetical order, will make the list easier to use.

8. How will the proposed changes effect land use and development under Title 33 Zoning Code?

As outlined in the existing provisions of Title 33, plants on the Nuisance Plants List cannot be installed in the Environmental Overlay Zone, the Greenway Overlay Zone, the Pleasant Valley Natural Resources Overlay Zone, and City-required landscaped areas.

Amendments to Title 33, the Zoning Code include:

  • Changing references to the Nuisance Plant List and the Prohibited Plant List to reflect the consolidation of these two lists into a single list called the Nuisance Plants List.
  • Clarifying that removal of groundcovers and shrubs on the Nuisance Plants List is required within City-required landscaping.
  • Clarifying that removal of groundcovers and shrubs on the Nuisance Plants List is required within Environmental Overlay Zones, Greenway Overlay Zones, and the Pleasant Valley Natural Resource Overlay Zones. Adding the requirement that trees on the Nuisance Plants List are required to be removed in the mitigation areas in these overlay zones. If the tree removal requirement cannot be met, the applicant must provide an alterative mitigation action.
  • Requiring invasive plant removal as part of the standards that must be met in a Plan Check process for development that encroaches upon Environmental Overlay Zones and the Pleasant Valley Natural Resource Overlay Zones.
9. How will the proposed changes effect property maintenance requirements under Title 29? Is there a penalty involved?

Changes to Title 29, the Property Maintenance Regulations, will require property owners to remove invasive plants listed on the Nuisance Plants List, Required Eradication List. There are 15 plants on this list. This prevents the proliferation of invasive plants by removing invasive plants that are not well-established in the Portland metropolitan area. The Bureau of Environmental Services (BES) Early Detection and Rapid Response team will provide property owners with free assistance to help remove these 15 plants, if found.

If the property owner declines City assistance, declines to remove the plants, and refuses to comply with the removal requirement, then the City would initiate the nuisance abatement process, in accordance with the abatement process identified in Title 29. The abatement process is handled by the Bureau of Development Services. The abatement process would be employed only when property owners do not agree to remove the specified plants. Based on similar programs in other jurisdictions, it is anticipated that such abatement cases would be rare.

10. What does it mean to be a watch species? Do the regulations apply to watch species? What if we find that a watch species becomes a problem?

The watch species are one of the five ranks assigned on the Nuisance Plants List. Some of these species are known to be invasive in other places; however, they are not yet known to occur in Portland. Some of the species on this list are present in Portland; however, they are either less invasive than rank “A-C” species or their level of invasiveness is still being evaluated. If a watch species becomes a problem, then the plant will be re-labeled with a different rank such as “A”. Rank “A” species are plants that are known to be invasive in the Portland metro region; however, they have limited distribution.

11. What if we disagree with a rank or we think that a species should be added or deleted from the Nuisance Plants List? How can the public influence this list?

The public can request changes to the list or changes to the ranks at any time by sending a written request to BPS. Potential changes might be collected over a period of time and processed in batches, depending on the nature of the changes and resource availability.


Currently, the Portland Plant List is an ordinance. The City proposes to re-establish the Portland Plant List as an administrative rule. This will be consistent with technical documents such as the Erosion Control Manual and the Stormwater Management Manual. Administrative rules provide a streamlined process for reviewing and making changes to technical documents such as the Portland Plant List. The public will still be provided the opportunity to comment on proposed changes to the administrative rules.


Changes to the Portland Plant List, including the Nuisance Plants List, will be made through an administrative rule process. The Bureau of Planning and Sustainability will coordinate review of potential modifications to the Portland Plant List. Potential modifications will be reviewed by at least three or more knowledgeable persons with botany, biology, landscape architecture, or other qualified backgrounds. BPS will inform key stakeholders of potential changes and provide opportunity for review and comment.

12. Is this project different than the Citywide Tree Project?

Yes. The Citywide Tree Project is a separate project from the Invasive Plant Policy Review and Regulatory Improvement Project. Please contact Morgan Tracy, at 503-823-6879 and to obtain information. See the BPS web page at:

13. How can I find more information about the Invasive Plant Policy Review and Regulatory Improvement Project?

You can find information on the BPS web page at: The web page includes project reports: the Proposed Draft Report and Recommendations to Planning Commission, dated October 9, 2009, and the Planning Commission Recommended Report to City Council, dated January 15, 2010. You can also find more information about the project on the BES web page at: At this web page, you can also find links to other information such as descriptions of invasive plants and the City’s Invasive Plant Management Strategy.

To get more information about the project, contact Tricia R. Sears, Bureau of Planning and Sustainability, at 503-823-1174 and

14. What are the next steps for this project?

On November 10, 2009, the Planning Commission approved the project. The Portland City Council held a hearing on the Invasive Plant Policy Review and Regulatory Improvement Project Report on February 3, 2010.


Council approved the code changes on February 10, 2010. Outreach and education to City employees and the public will continue. The proposed effective date of the amendments is July 1, 2010, with the exception of Section 33.430.140.L and Section 33.465.150.G, which will become effective on July 1, 2011.

The next phase of this project will continue the research and also address the following:

  • Coordinate with the Portland Plan (the City’s work in progress revision and update of the existing Comprehensive Plan) to clearly identify that references to watershed health improvement and habitat quality include invasive plant removal;
  • Evaluate the City’s involvement in a noxious weed control district and related establishment of a noxious weed law as outlined in ORS 570;
  • Update the Erosion Control Manual, the Stormwater Management Manual, and the Tree and Landscaping Manual to ensure consistency with the Nuisance Plants List.