Cold Hardiness of Grevillea in Western Oregon ; HortTechnology

Abstract

A cold hardiness evaluation of 57 cultivars and species of grevillea (Grevillea) was conducted from 2011 to 2014 in Aurora, OR, to assess landscape suitability in the Pacific Northwest United States. Plants were established using irrigation in 2011, but they received no supplemental water, mineral nutrients, or pruning from 2012 to 2014. Plants were evaluated for injury in Mar. 2012 and Jan. 2014 after winter cold events with minimum temperatures of -4 and -13 degrees C, respectively. Damage, at least on some level, occurred on most selections following their first winter after planting in 2011. During Winter 2013, further damage to, or death of, 33 grevillea cultivars or species occurred. The grevillea that exhibited the least cold damage and the most promise for landscape use and further evaluation in the Pacific Northwest United States were 'Poorinda Elegance' hybrid grevillea, southern grevillea (G. australis), cultivars of juniper-leaf grevillea (G. juniperina) including Lava Cascade and Molonglo, and oval-leaf grevillea (G. miqueliana), all of which exhibited minor foliage damage. ; Washington State Department of Agriculture Nursery License Surcharge program (Olympia, WA) ; We appreciate and acknowledge financial support from the Washington State Department of Agriculture Nursery License Surcharge program (Olympia, WA), as well as the donation of cutting material from the University of California, Santa Cruz, Arboretum, and the assistance of the staff at the Arboretum. Thanks are also due to Oregon State University Marion County Master Gardeners for assistance with plot establishment and data collection. ; Public domain authored by a U.S. government employee