Evaluation of Grevillea and Related Taxa for Use in Western Oregon Urban Landscapes, Poster Board #234

Grevillea is a genus of about 360 woody, evergreen shrubs or trees native primarily to Australia. Their habit ranges from prostrate and wide-spreading, upright shrubs and tree forms. The common name “spider flower” refers to the unusual flowers which are long and slender and borne in dense bunches. The flowers are found in shades of red, yellow or white. Most of the Grevillea cultivars that exist are not cultivated in the Pacific Northwest (PNW), or have been grown only by enthusiasts.  Rarely have Grevillea  and related taxa been used in landscaping and they are currently produced in only small numbers by specialty nurseries in the PNW. The Grevillea most commonly used in landscaping in the PNW are G. victoriae, G. juniperina cultivars, and other hybrid cultivars like ‘Canberra Gem’. The primary reason for lack of use is unawareness of this group of plants or the misperception that Grevillea lack hardiness or landscape adaptability here. To provide comparative data on the hardiness of these plants in western Oregon, a field evaluation of Grevillea and related plants was planted at the Oregon State University North Willamette Research and Extension Center in Aurora, OR on 19 August 2011.  A total of 58 accessions of Grevillea were planted, along with three Banksia accessions, two Hakea accessions and two Lomatia accessions. All accessions were laid out in a completely randomized design with four replications of each accession. The plot consists of four rows 4 m apart, with plants 1.5 m apart within the row. The plants were hand-watered at planting and overhead irrigated through early fall. No further irrigation or fertilizer was provided after this time. The winter of 2011–12 was mild, with a low temperature of 24 °F on 13 December 2011. Nevertheless, an assessment of cold injury to the collection on 12 March 2012 found many of the cultivars in the collection badly damaged or apparently dead from cold injury. Those that seemed to suffer the least injury included cultivars of G. victoriae, G. juniperina, and G. australis, as well as G. ‘Canberra Gem’ and G. ‘Poorinda Constance’. Given that these are already cultivated and regarded as some of the hardiest, these results were not surprising. However, other accessions that showed minimal injury included G. rivularis, G. lavandulacea ‘Penola’, Banksia marginata, B. integrifolia, Lomatia myricoides, and L. tinctoria.