Portland Plant List
Bureau of Planning, City of Portland, Oregon — June 1998
Adopted by Portland City Council — November 13, 1991
Effective — December 13, 1991, Ordinance No. 164838
Amended May 16, 1993, Ordinance No. 166572; September 21, 1994, Ordinance No. 168154; March 19, 1997 Ordinance 171000; June 24, 1998; March 2004.
Introduction
The Portland Plant List is an integral component of the City of Portland’s natural resource protection program. Native plants identified on the list are required within the City’s Environmental and Willamette River Greenway Zones; invasive or harmful plants (identified on the “Nuisance” or “Prohibited” Plant Lists) are prohibited.
Portland’s native plant policy is designed to ensure the continued viability and diversity of indigenous plant and animal communities, promote the use of plants naturally adapted to local conditions, and educate citizens about the region’s natural heritage and the values and uses of native plants.
A healthy native plant community serves many important functions: it provides habitat for native wildlife and preserves critical habitat for rare, threatened and endangered animals and plants; enhances air and water quality by trapping airborne particulates and by filtering sediments and pollutants from runoff before they enter streams and aquifers; stabilizes stream banks and hillside slopes, and dissipates erosive forces; ameliorates the local microclimate, and reduces water and energy needs; and provides scenic, recreational and educational values which, in turn, enhance Portland’s livability. Native plants are part of the region’s natural heritage.
In February 1986, the Greenway Plant List was developed in consultation with local ecologists, biologists and naturalists. Later that year, this list was adapted for the Columbia River Corridor area. Use of native plants from the list first became a requirement within the Willamette River Greenway Zones, and was later required within the Environmental Zones when adopted in 1989 for the Columbia Corridor. Soon thereafter, a Technical Advisory Committee (TAC) was established to review and expand the list to cover all of Portland. As part of that review, the TAC identified the need to create categories for native, nuisance and prohibited plants. The expanded “Portland Plant List,” covering native and nuisance plants throughout the City, was adopted by the Portland City Council on November 13, 1991.
Amendments passed on May 26, 1993 and September 21, 1994 further refined and expanded the List, and added prohibited plants. In July, 1995, the list was updated to include name changes from recent references, as cited in Appendix III of The Jepson Manual. In March 1997, the list was updated to reflect recent scientific findings on native plants in the region.
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The Three Lists: Native, Nuisance & Prohibited
The Portland Plant List is divided into three sections: native plants, nuisance plants and prohibited plants. These sections are summarized below, followed by a review of the procedures for modifying the plant lists.
The Native Plants section is a listing of native plants historically found in the City of Portland. The list divides the plants into three groups: trees and arborescent shrubs, shrubs and ground covers. For each group, the list includes the scientific (Latin) name of a species, its common name, its wetland indicator status, and its associated habitat type. The habitat types are: wetland, riparian, forest, forested slopes, thicket, grass and rocky.
The Nuisance Plants section is a listing of plants found in the City of Portland which can be removed manually without requiring an environmental review or greenway review. Other local, state or federal laws may still regulate removal of certain plants on this list. Nuisance plants may be native, naturalized or exotic. They are divided into two groups: plants which are considered a nuisance because of their tendency to dominate plant communities, and plants which are considered harmful to humans. Each group identifies the scientific and common plant names and their indicator status.
The Prohibited Plants section is a listing of plants which the City of Portland prohibits from use in all reviewed landscaping situations within the City limits. These plant species pose a serious threat to the health and vitality of native plant and animal communities. Manual removal of these plants is exempt from land use review.
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Modification of Lists
Plants may be added to or removed from the Native Plant List or Nuisance Plant List as follows. When a request to amend either list is received, the Bureau of Planning will consult with three or more knowledgeable persons with botany, biology or landscape architecture backgrounds to determine whether the requested change is warranted. This decision will be forwarded to the applicant and will be final. The primary source for native plant determination is the five volume set, Flora of the Pacific Northwest, by Hitchcock and Cronquist.
Adding to or removing plants from the Prohibited Plant List must be done through a legislative procedure as provided in Chapter 33.740 of the Zoning Code.
Native Plants
This section provides a list of native plants historically found in the City of Portland. The list includes several plants known to occur within the Urban Growth Boundary or not more than ten miles from Portland and expected to occur within the City based on the presence of suitable habitat, the judgment of local botanical experts, or the range descriptions found in Hitchcock’s Flora. The list divides plants into three groups: trees and arborescent shrubs, shrubs and ground covers. Arborescent shrubs are indicated with an “ª” superscript; these shrubs may not be used to meet Title 33 or Title 34 standards, criteria or conditions of approval which require trees.
The Indicator Status refers to the frequency with which a plant occurs in a wetland; the categories are derived from the List of Plant Species That Occur In Wetlands: Northwest Region (USFWS, Biological Report 88(26.9), 1988). The status of certain plants was revised using the 1993 Supplement to the List (for Region 9). The indicator categories are as follows:
Obligate Wetland (OBL): Occur almost always (estimated probability >99%) under natural conditions in wetlands.
Facultative Wetland (FACW): Usually occur in wetlands (estimated probability 67%-99%), but occasionally found in non-wetlands.
Facultative (FAC): Equally likely to occur in wetlands or non-wetlands (estimated probability 34%-66%).
Facultative Upland (FACU): Usually occur in non-wetlands (estimated probability 67%-99%), but occasionally found in wetlands (estimated probability 1%-33%).
Obligate Upland (UPL): Occur in wetlands in another region, but occur almost always (estimated probability >99%) under natural conditions in non-wetlands in the Northwest region.
A positive (+) sign used with an indicator category means that the plant occurs more frequently at the higher end of the range (more frequently found in wetlands). For example, FACW+ indicates that the plant is typically found in Northwest wetlands with an estimated probability of 83%-99%. A negative (-) sign indicates a frequency toward the lower end of the range (less frequently found in wetlands). An NI (no indicator) was recorded for those species for which insufficient information was available to determine an indicator status. If no category or symbol is indicated for a plant then either the plant does not occur in wetlands, or the species was not reviewed by the 1988 or 1993 interagency panels that developed the list.
The Habitat Types are wetland, riparian, forest, forested slopes, thicket, grass and rocky. “Wetland” includes all forms of wetlands found in Portland. “Riparian” includes the riparian areas along the Willamette and Columbia Rivers, and other streams in Portland. “Forest” refers to upland forested areas with little or no slope. “Forested slopes” refers to steeply sloping upland forests such as the west hills and various buttes found in Portland. “Thicket” refers to edges of forests and meadows and includes hedgerows and clumps of vegetation that may be found in meadows. “Grass” refers to open areas or meadows. It may also include clearings in forested areas. “Rocky” refers to rocky upland areas, and may include cliffs.
The information on habitat types is intended to provide general guidance for appropriate planting locations; certain plants, however, have highly specialized habitats which may make them appropriate for use only in specific areas of the City. For example, the Columbia River Willow (Salix fluviatilis) normally occurs only along the Columbia River and is not appropriate for use in all “wetland” or “riparian” habitats throughout the City. For this reason, it may be helpful to consult with Bureau of Planning staff, local botanists or published sources when preparing a planting plan.
Sources of Native Plants
Native plants can be acquired through many local and specialty plant nurseries in the Portland area. A useful native plant directory, Hortus Northwest, is available at the Bureau of Planning or by writing Hortus Northwest, P.O. Box 955, Canby, OR 97013. Occasionally, particularly for large orders or less common plants, growers will need time to propagate and raise plants before they are ready for installation. For this reason, growers may need advance notice of plant orders and project timelines should allow adequate time to fill such orders.
