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Thirty-eight species, cultivars, and hybrid selections of ceanothus (Ceanothus 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 Ceanothus thyrsiflorus var. griseus, C. thyrsiflorus var. griseus ‘Yankee Point’, Ceanothus hearstiorum, and C. thyrsiflorus ‘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, Ceanothus cuneatus var. rigidus ‘Snowball’ and Ceanothus gloriosus ‘Heart's Desire’ made effective groundcovers only 0.6 and 0.2 m tall, respectively.
Ninety-three species, cultivars, and hybrid selections of rockrose (Cistus spp., Halimium spp., and ×Halimiocistus spp.) were evaluated for growth, flowering, and cold hardiness in a landscape trial in Aurora, OR, from 2004 to 2009. Plants were irrigated to aid establishment when planted in summer 2004, but thereafter were not watered, fertilized, or pruned throughout the trial. Cold damage was recorded following freezing events in Feb. 2006 and Dec. 2008 in which low temperatures were 20 and 17 °F, respectively. Those plants that consistently suffered the most cold damage were Halimium atriplicifolium, Cistus creticus ssp. creticus ‘Tania Compton’, Cistus ×pauranthus, and Cistus albidus forma albus. Other plants showed cold damage related to poor vigor. The length of the flowering period and foliage quality varied widely among plants in the evaluation. The plants with the longest flowering period were Halimium ×pauanum, Cistus inflatus, Cistus ×pulverulentus ‘Sunset’, and ×Halimiocistus ‘Ingwersenii’, all of which flowered for more than 55 days. Plant form and foliage quality declined drastically for some plants during the evaluation. Those that retained the best foliage quality included Cistus ×obtusifolius, Cistus ×laxus, Cistus salviifolius ‘Gold Star’, Cistus ‘Gordon Cooper’, Halimium lasianthum ‘Sandling’, Halimium ‘Susan’, and ×Halimiocistus sahucii. Based on ratings of foliage and bloom time, as well as hardiness, several Cistus are recommended as drought-tolerant groundcovers, including Cistus ×gardianus and C. ×obtusifolius. Cistus ×laxus, C. inflatus, Cistus ‘Gordon Cooper’, Cistus ‘Ruby Cluster’, and Cistus ‘Snow Fire’ are suggested as tall groundcovers or landscape specimens. Several Halimium are recommended for landscape use, including H. lasianthum ‘Sandling’, Halimium ‘Susan’, H. ×pauanum, and ×Halimiocistus ‘Ingwersenii’.
`Redcrest' plants were renovated at 2, 4, 6, 8, or 10 weeks after harvest (WAH) from July 1 to Aug 26, 1992 and July 7 to Sept 1, 1993, plus an unrenovated control. Data on fall yield, maximum cold hardiness, and summer yield and berry weight were collected. For maximum cold hardiness, crowns were subjected to controlled freezing (-8, -11, -14, -17 or -20°C) and then evaluated by oxidative browning. Fall yield in 1993 was greater than in 1992. In 1992, fall yield was comparable for all renovation dates except the latest, 10 WAH. Unrenovated plants tended to have a lower fall yield than renovated plants. In 1993, plants renovated 2, 4, or 6 WAH had higher yields than control or late-renovated plants. Fall yield was not correlated with summer yield in 1993. Plants renovated 4 WAH had a higher summer yield in 1993 than unrenovated plants or those renovated at other times, which all had similar yields. Date of renovation had no effect on berry weight or percent fruit rot. Unrenovated plants and those renovated 2 or 4 WAH were hardier in winter 1992/93 than those renovated later.
In July 1999, adult stages of root weevils were established in 1-gal containers planted with Rhododendron `PJM.' Each pot was inoculated with one black vine weevil, three rough strawberry root weevils, and four strawberry root weevils. On 12 July, insecticide spray treatments were applied. Treatments were evaluated for percent adult mortality at 7 and 14 days after treatment (DAT). Black vine weevils were more sensitive to the insecticides studied than either strawberry root weevil or rough strawberry root weevil. There was considerable mortality of the black vine weevils and rough strawberry root weevils in the untreated plots by 14 DAT. Talstar Flowable (bifenthrin), Alta (deltamethrin), Topside (lamda cyhalothrin), and CGA 293 343 (thiamethoxam) all gave 100% control 7 DAT. Additionally, Closure (bendiocarb) and acephate gave 75% or better control at 7 DAT. Rough strawberry root weevil had 100% mortality in only the Alta-treated plots at 7 DAT, followed by 93% and 80% mortality in Topside and acephate-treated plots, respectively. Mortality of the strawberry root weevils in the untreated plots by 14 DAT remained relatively low. Strawberry root weevils were more resistant to the applied insecticide treatments. Only Topside-treated plots had 90% or greater mortality at 7 DAT, followed by Talstar (60%), Alta (58%), and acephate (54%). Topside-treated plots had 90% or greater mortality at 14 DAT followed by Talstar (76%), Alta (68%), and Closure (60%). Combined root weevil species mortality showed highest mortality at 7 DAT in Topside-treated plots (87% or greater), followed by Alta (74% or greater), and acephate (73%).
Primocanes were cut at ground level at one-month intervals from late April to late July 1991 and 1992. An uncut control was included. Four canes per plant were trained either in August or the following February, the others being removed and measured. Yield data were collected and yield components measured in 1992 and 1993. Cane diameter, main cane length and branch cane length per plant generally declined with later suppression date. Consequently, yield per meter of cane declined with later suppression date. However, cane number and total plant main cane length were greater for all suppression treatments and percent budbreak increased with later suppression date. As a result, April- and May-suppressed plants had increased-yields compared to control plants in both 1992 and 1993, as did June-suppressed plants in 1993. August-trained plants had significantly higher yields than February-trained in both years, primarily because of increased budbreak. The basal section of canes was the most productive, because of increased budbreak and branch cane production.
Stem and bud tissues of promocanes from more than 260 Rubus genotypes were evaluated for mid-winter cold hardiness after laboratory freezing in January 1990. T50 values were calculated for cane samples of red, yellow, black and purple raspberry, and blackberry cultivars, hybrids and species. Red raspberries exhibited the hardiest stem tissue, although several purple raspberries (Rubus sp. cvs. Brandywine, Royalty) survived as low as -33 C. Fall fruiting red raspberries, such as R. idaeus L. cvs. Zeva Remontante, Indian Summer, St. Regis, and Fallred, survived from -23 to -25 C. Summer-bearing cultivars, Canby and Puyallup, survived to -30 C. Stems of several black raspberries (R. occidentalis L. cvs. New Logan, Bristol) survived to -27 C. Stems of the hardiest blackberry cultivars, (R. sp. cvs. Black Satin, Smoothstem) survived to -22 C. In most genotypes the region of the bud at the axis of the stem was less hardy than tissues within the bud scales. Buds tissue was 2 to 10 C less hardy than stem tissue. Field plants were also visually rated for cold injury following record low temperatures occurring in 1989, 1990, and 1991.
Primocanes of `Marion' trailing blackberry plants (Rubus spp.) were suppressed by cutting them off at ground level in either late April, May, June, or July 1991 and 1992. A control was included in which primocanes were not cut. Four canes per plant were trained in either August or February, with all other canes being removed and measured. Yield data were collected in 1992 and 1993, after which yield components were measured. Cane diameter was greatest for unsuppressed plants and declined with later primocane removal date. Cane length was greatest for unsuppressed and April-suppressed plants. Internode length decreased and main cane percent budbreak increased with later suppression date. Cane number and total main cane length per plant were increased in April-, May-, and June-suppressed plants in 1992 and for April- and June-suppressed plants in 1993. Consequently, yield of April-suppressed plants exceeded that of unsuppressed plants in 1992. Yield of April-, May-, and June-suppressed plants exceeded that of unsuppressed plants in 1993. August-trained plants yielded 46% more than February-trained plants, primarily because of higher percent budbreak on main canes. August-trained plants also produced longer canes with more nodes and a greater number of fruit per main cane lateral.
Primocanes of `Marion' trailing blackberry plants were suppressed by cutting them off at ground level in either late April, May, June, or July 1991 and 1992. An unsuppressed control was included in which primocanes were not cut. A single cane was removed from each replication of the five primocane suppression dates at monthly intervals from mid-November to mid-February 1991-92, and from mid-November to mid-January 1992-93. One-node samples were exposed to controlled freezing at temperatures of 4, -6, -9, -12, -15, and -18C in November through February. In December and January, the-6 temperature was replaced with-21C. After 5 days at room temperature following freezing, growing point, budbase, vascular, and pith tissues were evaluated for tissue browning on a 1 to 5 scale. The LT50 developed for each suppression date was compared to the control. July-suppressed plants were generally hardiest for all tissues. June-suppressed plants were somewhat less hardy than July-suppressed plants, while April-, May- and unsuppressed plants were comparable and least hardy. Cane tissues of July-suppressed and unsuppressed plants had a higher level of soluble carbohydrates than other suppression dates.
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 °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.
A collaborative project between the Oregon State University Extension Service, and the green industry and allied professional organizations resulted in an educational seminar series for landscape professionals. In 2003 and 2004, the seminar series consisted of seven 3.5-hour sessions covering a range of horticultural topics and capitalized on expertise of extension personnel and green industry professionals. After the 2004 series, a survey was sent to all participants to determine attendance, overall evaluation, usefulness and applicability of information, participant learning, and behavior change as a result of the seminars. The response rate was 31%. Overall, participants gave the seminars a positive rating. A majority (83%) of respondents reported they had applied information learned at the seminar(s), and showed a significant increase in understanding of a subject as a result of participating in the seminar(s). Further, 98% of those who applied this information reported making multiple changes to their practices or recommendations to clients in the 6 months following the seminars.