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Diversity of genera
In this publication, 33 genera are discussed. A mix of trees is offered in order to meet the wide variability of climates and soil types across the state. The species listed in Tables 2–5 represent some of the most highly suited genera, species, and cultivars for different regions of the state. Data for these tables was generated by reviewing tree planting lists provided by the City of Seattle (2014), City of Vancouver (2012), City of Spokane (2014), Washington State University Chelan county (Dinius 2009), the City of Pasco (2016), the City of Bellingham (2010), and the City of Tacoma (2014). None of the selections offered are considered invasive, according to the US Department of Agriculture Natural Resource Conservation Service (NRCS 2016). Mature tree height and width data were derived from temperature zone land-grant university references.
Importance of Conifers
The native Pacific Northwest forest is primarily composed of evergreen trees, with lesser percentage of deciduous trees. Dense stands of Douglas fir and Western red cedar predominate in areas west of the Cascades, while Ponderosa pine, Lodgepole pine, and Western larch occur on the east side. In western Washington, many of the native stands of Douglas fir have been severely reduced, especially in the Puget Sound area, due to the increase in population and resultant development. Currently 31% of the forest in western Washington is comprised of evergreens, with the remaining 69% consisting of deciduous trees. Urban foresters in western Washington understand the need to further increase the percentage of conifers where appropriate.