Attachment A.2 <br />Willamette River Greenway Code Amendments (CA 22-1) <br />City of Eugene <br />Native Landscape Buffer <br />February 9, 2023 <br />whose Tree Density Standards require 10x10 foot minimum planting area for large canopy trees.' The City of Portland's <br />Tree and Landscaping Manual also recommends an 8-foot minimum planter width for several large canopy tree species that <br />also appear in Exhibit F.3 <br />Recommended spacing for shrubs also varies by species but generally falls in the range of estimated mature height. The L-2 <br />Low Screen Landscape Standard requires "[l]ow shrubs to form a continuous screen at least 30 inches high within 3 years <br />and maintained at a height not to exceed 42 inches." Shrubs that fall within the range of 2-4 feet tall will often require <br />approximately 2-4 feet of space to accommodate growth. To achieve a denser screen, low hedge plants can be planted <br />approximately 18 inches apart.4 Based on these findings, the proposed 10-foot landscape buffer width is sufficient to <br />accommodate the largest permitted canopy trees and low shrubs required to meet the L-2 Low Screen Landscape Standard. <br />NATIVE PLANT LIST <br />The proposed approval criteria require the landscape area to "be planted exclusively with native plants included on the <br />City's adopted list of plant species for sites at or below 500 feet in elevation, attached as Exhibit F to Ordinance No. 20351." <br />Approved species on the list have been selected for suitability in riparian conditions in close proximity to the Willamette <br />River. The list includes 16 tree species, 29 shrub species, and other vine, herbaceous, grasses, sedges, and rushes species. <br />The list includes a key to site suitability and applies to each species, that notes whether the species is suitable for shallow <br />water, water's edge, lower bank, and/or upper bank site conditions. Upper bank (UB) is defined as terraces above the <br />ordinary high-water line. The proposed 10-foot native landscape buffer would apply in both lower and upper bank <br />conditions given the variability of topography along the river's edge within proposed Willamette River Greenway Setback. <br />Landscape Architects, including a certified Arborist, from Cameron McCarthy reviewed the plant list for consistency with <br />native plant communities commonly found along the riparian corridor of the Willamette River and variety, in application <br />responding to different site conditions, and availability. The list is comprehensive and provides a sufficient range of species <br />and options to respond to site conditions, conformance with the L-2 standards, and commercial availability. Updating the <br />list periodically to respond to climate change and new species information is recommended but not necessary at this time. <br />REFERENCES <br />1 City of Eugene Parks and Open Space (2020). Approved Street Tree List and Planting Guide. <br />2 City of Portland Bureau of Development Services (2019). Tree Code Information Guide. <br />a City of Portland Bureau of Development Services (2017). Tree and Landscaping Manual. <br />° Washington State University Master Gardener Program (2015). Spacing of Landscape Plants. <br />CAt~EgeON MCARTHY Page 2 <br />24 0 <br />