Variety Trials
Total Page：16
File Type：pdf, Size：1020Kb
Mountains. Halimium are confined to the western Mediterranean and Greece. The climate in which these plants orig- inated is Mediterranean, with mild, rainy winters and warm to hot, dry summers. Throughout this region, rockroses form an important compo- Variety nent of the xeric maquis shrub com- munity. All the species are evergreen shrubs and range in habit from pros- trate to sprawling or, in some cases, Trials erect large shrubs. Although evergreen, they are considered drought semide- ciduous (malacophyllous), possessing the ability to develop different types of leaves in summer and winter, and to Growth, Flowering, and Cold Hardiness of drop leaves during prolonged periods of drought (Acosta et al., 1997). As Rockrose in Western Oregon a result, rockroses are well adapted to growing in hot, dry situations, and in 1,3 2 relatively poor soils. Neil C. Bell and James Altland Western Oregon is characterized by a climate with a mild, wet winter ADDITIONAL INDEX WORDS. Cistus, Halimium, drought, landscape, shrubs and a pronounced summer drought and is comparable to the cool humid SUMMARY. Ninety-three species, cultivars, and hybrid selections of rockrose (Cistus Mediterranean climate characteristic of spp., Halimium spp., and ·Halimiocistus spp.) were evaluated for growth, southern France (Nahal, 1981). Nev- flowering, and cold hardiness in a landscape trial in Aurora, OR, from 2004 to ertheless, few rockroses are grown or 2009. Plants were irrigated to aid establishment when planted in summer 2004, but thereafter were not watered, fertilized, or pruned throughout the trial. Cold used extensively in landscapes in west- damage was recorded following freezing events in Feb. 2006 and Dec. 2008 in ern Oregon or Washington. The most which low temperatures were 20 and 17 °F, respectively. Those plants that commonly grown are Cistus ·hybridus consistently suffered the most cold damage were Halimium atriplicifolium, and Cistus ·purpureus,bothofwhich Cistus creticus ssp. creticus ‘Tania Compton’, Cistus ·pauranthus, and Cistus albidus may be used as tall groundcovers or forma albus. Other plants showed cold damage related to poor vigor. The length specimen shrubs. The genus has suf- of the flowering period and foliage quality varied widely among plants in the fered from a reputation of being short- evaluation. The plants with the longest flowering period were Halimium lived and tender. This reputation ·pauanum, Cistus inflatus, Cistus ·pulverulentus ‘Sunset’, and ·Halimiocistus maypartlybearesultofthelimited ‘Ingwersenii’, all of which flowered for more than 55 days. Plant form and foliage selections cultivated, but may also be quality declined drastically for some plants during the evaluation. Those that retained the best foliage quality included Cistus ·obtusifolius, Cistus ·laxus,Cistus attributed to plants being grown in salviifolius ‘Gold Star’, Cistus ‘Gordon Cooper’, Halimium lasianthum ‘Sandling’, landscapes that are watered regularly in Halimium ‘Susan’, and ·Halimiocistus sahucii. Based on ratings of foliage and summer, a common practice in sum- bloom time, as well as hardiness, several Cistus are recommended as drought- mer-dry areas such as western Oregon. tolerant groundcovers, including Cistus ·gardianus and C. ·obtusifolius. Cistus Published studies on hardiness ·laxus, C. inflatus, Cistus ‘Gordon Cooper’, Cistus ‘Ruby Cluster’, and Cistus ‘Snow of rockroses are rare and tend to be Fire’ are suggested as tall groundcovers or landscape specimens. Several Halimium anecdotal in nature. Johnson (1947) are recommended for landscape use, including H. lasianthum ‘Sandling’, commented briefly on the relative Halimium ‘Susan’, H. ·pauanum, and ·Halimiocistus ‘Ingwersenii’. hardiness of some common Cistus in the United Kingdom after cold weather in Feb. 1947. Mulligan ockroses are genera of ever- previous names, those will be retained (1953) evaluated 18 species and green, woody shrubs of the for the purposes of this evaluation. cultivars of Cistus and ·Halimiocistus Rfamily Cistaceae, native princi- The distribution of Cistus ranges in Seattle, WA, from 1949 to 1953 pally to the Mediterranean basin. The from the Canary Islands to the Caucasus and found significant variations in 20 species of Cistus and seven species of Halimium have remained as sepa- rate genera since the 18th century (Page, 2009). The hybrid of these Units two genera (·Halimiocistus)contains To convert U.S. to SI, To convert SI to U.S., three species. Recently, Demoly multiply by U.S. unit SI unit multiply by (2006) has proposed assigning all the 0.4047 acre(s) ha 2.4711 0.3048 ft m 3.2808 Halimium and ·Halimiocistus to Cis- 2.54 inch(es) cm 0.3937 tus. As the plants in this evaluation were 28.3495 oz g 0.0353 obtained and evaluated under their (°F – 32) O 1.8 °F °C(1.8·C) + 32 652 • June 2010 20(3) hardiness and ornamental qualities. cuttings of the other 83 plants were and width perpendicular to the widest Mundie (2001) evaluated Cistus in obtained from the National Collection diameter) were measured at establish- northern England from 1997 to of Cistus and Halimium held by R. ment and again each year in fall. Flow- 2001. However, most research on re- Page in Leeds, UK, in Oct. 2003. ering was evaluated by rating bloom sponse of rockroses to winter condi- These cuttings, and those from the on the plants weekly on a 0 to 5 scale. tions has focused on physiological stock plants, were stuck in early Oct. A rating of ‘‘0’’ was given to plants responses of the plants to cool winter 2003 in 4 perlite:1 peatmoss (v/v) mix with no open flowers; ‘‘1’’ meant at temperatures, not necessarily their at the Oregon State University (OSU) least one open to less than 20% specific cold hardiness. Various studies North Willamette Research and Ex- bloom; ‘‘2’’ meant 20% to less than have demonstrated changes in chloro- tension Center (NWREC) in Aurora. 40% bloom; ‘‘3’’ meant 40% to less phyll content (Nunez-Olivera et al., Cuttings were rooted in a polyethyl- than 60% bloom; ‘‘4’’ meant 60% to 1994), pigments and antioxidants ene-covered hoop house, using bot- less than 80% bloom; ‘‘5’’ meant 80% (Garcia-Plazaola et al., 2000), and tom heat, but no mist. Five cultivars bloom or greater and was reserved for photosynthesis (Oliveira and Penuelas, failed to root in sufficient number and shrubs whose foliage was obscured by 2004). These studies do not typically were not included in the evaluation. bloom. relate these changes to hardiness, al- Rooted cuttings were potted into 6- Cold hardiness evaluations were though in a study of physiological re- inch square nursery pots in Mar. done in early spring after mild weather sponses of eight Mediterranean shrubs 2004 and were top-dressed with 10 g allowed for full symptom development to winter stress, Varone and Gratani of 18N–3.5P–6.6K controlled-release from any prior cold injury. Data were (2007) found Cistus incanus (syno- fertilizer (ApexÒ Evergreen; Pursell collected only in Apr. 2006 and in Apr. nym = Cistus creticus) to be one of Technologies, Sylacauga, AL). Plants 2009, as there was no apparent dam- theleastcoldhardyandsuggestedthat were maintained until planting in the age following Winter 2004–05, 2006– in addition to summer drought, winter evaluation site on 22 June. 07, and 2007–08. Cold damage was temperatures might represent an addi- The evaluation site was a south- rated on a 0 to 5 scale, adapted from tional limitation to Mediterranean spe- facing slope at NWREC (lat. 45°57#N, Lonard and Judd (1991) with ‘‘0’’ in- cies productivity. The objective of our long. 122°45#W, 155 ft elevation). dicating no damage; ‘‘1’’ meant minor study was to determine the growth and The evaluation site was 0.5 acre. leaf damage (browning); ‘‘2’’ meant relative hardiness of rockrose species The soil series was a Willamette silt leaf and stem damage restricted to the and cultivars under western Oregon loam. Before planting, the site was exterior 30% of the plant; ‘‘3’’ meant conditions. subsoiled to a depth of 1 ft, and was leaf and stem damage to the exterior then disked to break up and level the 60% of the plant; ‘‘4’’ meant the plant Materials and methods soil. The trial was divided into 12 rows was killed to the crown with resprout- Species, selections, and cultivars 185 ft long, spaced 10 ft apart, orien- ing; and ‘‘5’’ indicated the plant was of rockroses were from two main tated north to south. Individual plants dead. Regional weather data were sources. A total of 98 species and cul- were randomly assigned to rows and obtained from the U.S. Bureau of tivars was obtained from nursery sour- planted at an in-row spacing of 5 ft. Reclamation Agrimet weather station ces in California or from the United Plants were planted in a completely at NWREC, located 400 ft from the Kingdom. Fifteen of these were ob- randomized design with four replicates. trial site (U.S. Bureau of Reclamation, tained as stock plants from nurseries in After planting, plants were wa- 2009). California in Sept. 2003. These plants tered in by hand, and then received Foliage quality and overall plant were grown on through early Octo- periodic overhead water sufficient to formwereratedona1to5scale,with ber, at which time 4-inch-long tip keep the top 6 inches of soil moist ‘‘1’’ meaning a plant with less than 20% cuttings were taken. Unrooted tip through the end of Aug. 2004. Plants of a full canopy, indicating a sparsely received no supplemental irrigation foliated plant with poor form and after this time. No fertilizer was ap- dieback; ‘‘2’’ meant 20% to 40% can- The authors appreciate and would like to acknowl- edge financial support from the Agricultural Research plied at planting or thereafter for the opy, with foliage thinly distributed Foundation of Oregon State University (Corvallis, duration of the trial. Plants were not over the canopy and some dieback; OR), as well as the donation of plants by Anderson pruned.