Evaluation of camellia cultivars and selections for growth, cold hardiness, flowering, and disease resistance in Tennessee, USA

Authors: PARAJULI, MADHAV - Tennessee State University; Shreckhise, Jacob - Jake; FARE, DONNA - Retired ARS Employee; Moore, Benjamin; LIYANAPATHIRANAGE, PRABHA - Tennessee State University; SUBEDI, PRATIMA - Tennessee State University; BAYSAL-GUREL, FULYA - Tennessee State University

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2023
Publication Date: 11/20/2023
Citation: Parajuli, M., Shreckhise, J.H., Fare, D., Moore, B.T., Liyanapathiranage, P., Subedi, P., Baysal-Gurel, F. 2023. Evaluation of camellia cultivars and selections for growth, cold hardiness, flowering, and disease resistance in Tennessee, USA. HortScience. 58(12):1533-1541. https://doi.org/10.21273/HORTSCI17430-23.
DOI: https://doi.org/10.21273/HORTSCI17430-23

Interpretive Summary: Ornamental camellias are a staple in Southeastern U.S. landscapes, prized for their glossy, evergreen foliage and eye-catching flowers that emerge in fall or winter when few other shrubs are blooming. In Middle Tennessee and other regions of the US that endure occasional sub-zero (°F) temperatures, camellias are seldom used due to their marginal cold-hardiness. USDA-ARS scientists teamed up with Tennessee State University to conduct a nine-year evaluation of 24 camellia vareties to assess their growth, cold hardiness, flowering, and disease resistance in McMinnville, TN. The researchers found marked differences in low-temperature damage among cultivars and selections trialed, with April Remembered, April Rose, Arctic Snow, Ashton’s Ballet, Autumn Carnival, Autumn Spirit, Elaine Lee, Survivor, and a C. chekiangoleosa selection least affected by winter low temperatures. While severity of several diseases varied among the cultivars, disease symptoms were rarely severe enough to have warranted a pesticide treatment. Cold-hardy cultivars and selections identified in this research may be used in camellia breeding programs to incorporate cold-hardiness into new varieties.

Technical Abstract: Susceptibility to low-temperature injury and diseases is a major concern associated with ornamental camellia production. To comprehensively understand their growth, cold hardiness, flowering, and disease resistance, 24 camellia (Camellia spp. and hybrids) cultivars and selections were evaluated in McMinnville, TN (USDA Plant Hardiness Zone 7a). In March 2011, camellias were planted in the field plots. Plant height and canopy width were measured annually from 2011 to 2019 and low temperature damage was recorded in 2014 and 2023. The flowering duration was recorded each year from 2011 to 2020. The Camellia Yellow Mottle Virus, monochaetia leaf spot (Monochaetia sp.), edema, flower blight (Ciborinia camelliae), and flower spot (Botrytis cinerea) severity (% affected) were evaluated from Oct. to Nov. in 2016 and 2017. The season-long area under the disease progress curve (AUDPC) was calculated. Cultivars Artic Snow and Pink Icicle exhibited the greatest height, and Autumn Spirit, Elaine Lee, Artic Snow, and Survivor had the widest canopy width, while Shishigashira had the lowest height and canopy width. Cultivars April Remembered, April Rose, Artic Snow, Ashton’s Ballet, Autumn Carnival, Autumn Spirit, Elaine Lee, Survivor, and a C. chekiangoleosa selection were least affected by winter low temperatures, while Korean Snow, One Alone, Pink Icicle, Shishigashira, and a C. sasanqua selection were severely damaged. The cultivar, Artic Snow flowered most reliably (6 out of 8 years) while April Remembered, April Rose, Ashton’s Ballet, Autumn Spirit, and Survivor flowered 5 times. Cultivars Korean Fire, Classic Pink, Maroon Mist, and Spring’s Promise displayed the highest virus severity and AUDPC. The cultivar Artic Snow, the C. sasanqua selection, and the C. chekiangoleosa selection had no viral symptoms. The C. sasanqua selection and ‘Red Aurora’ were significantly impacted by edema disorder, with severity ratings of ~43% and 26%, respectively. Monochaetia leaf spot severity was highest in cultivars Red Aurora and Spring’s Promise, whereas Anacostia, Artic Snow, Ashton’s Ballet, Autumn Spirit, Classic Pink, Kuro Delight, One Alone, Pink Icicle, Shishigashira, and Survivor exhibited the least monochaetia leaf spot severity and AUDPC. Flower blight and flower spot were observed only in cultivars Artic Snow and Survivor. These findings will aid landscapers and nursery growers in selecting and managing camellia cultivars effectively.