Evaluation of Growth, Flowering, and Cold Hardiness of Ceanothus in Western Oregon

Abstract

<jats:p>Thirty-eight species, cultivars, and hybrid selections of ceanothus (<jats:italic>Ceanothus</jats:italic> spp.) were evaluated for growth, flowering, and cold hardiness in a landscape trial in Silverton, OR, from 2001 to 2005. Plants were only irrigated for establishment in Summer 2001 and were not pruned or fertilized throughout the trial. Several cultivars showed dieback and leaf damage after 22 °F cold events in late October and early Nov. 2002 and 2003, the most severely affected of which were <jats:italic>Ceanothus thyrsiflorus</jats:italic> var. <jats:italic>griseus</jats:italic>, <jats:italic>C. thyrsiflorus</jats:italic> var. <jats:italic>griseus</jats:italic> ‘Yankee Point’, <jats:italic>Ceanothus hearstiorum</jats:italic>, and <jats:italic>C. thyrsiflorus</jats:italic> ‘Snowflurry’. Among the cultivars evaluated, those recommended for early bloom are ‘Ray Hartman’ and ‘Blue Jeans’. Several cultivars are effective drought-tolerant groundcovers, including ‘Wheeler Canyon’, ‘Joyce Coulter’, and ‘Joan Mirov’. Among the smaller-growing plants, <jats:italic>Ceanothus cuneatus</jats:italic> var. <jats:italic>rigidus</jats:italic> ‘Snowball’ and <jats:italic>Ceanothus gloriosus</jats:italic> ‘Heart's Desire’ made effective groundcovers only 0.6 and 0.2 m tall, respectively.</jats:p>

Cold Hardiness of Grevillea in Western Oregon

“…Injury to specific cultivars varied between the two cold spells evaluated in this study; in some cases, they varied considerably. This was seen to some extent in previous landscape studies of woody plants (Bell, 2009;Bell and Altland 2010). Although there is considerable literature about the variations in the cold hardiness of woody plants between seasons within a given year, no work has addressed the causes of variation in hardiness of individual plants between growing seasons.…”