Submitted to: Southern Nursery Association Research Conference
Publication Type: Proceedings
Publication Acceptance Date: 8/10/2005
Publication Date: 12/15/2005
Citation: Jones, K.D., Reed, S.M. 2005. Recent developments in Hydrangea interspecific hybridization. Proceedings of the Southern Nursery Association Research Conference. 50:643-645. Interpretive Summary: Hydrangeas are among the most popular flowering shrubs, with annual U.S. sales of approximately $32 million. While several species are cultivated and many cultivars are available, little work has been done on combining the best characteristics from different members of this genus via interspecific hybridization. This report describes the production of a hybrid between H. arborescens, which is one of the most cold-hardy members of the genus, and H. involucrata, which produces lavender-blue flowers. Production of this hybrid represents the first step in combining cold hardiness and flower color in Hydrangea. This work may eventually lead to the development of superior cultivars and expanded sales of Hydrangea in colder areas of the U.S.
Technical Abstract: Hydrangea arborescens, or smooth hydrangea, offers large corymbs of pure white flowers in early summer and is cold-hardy to zone 4. Hydrangea involucrata produces lavender-blue flowers in mid-summer, but is only rated as hardy to zone 6 or 7. The objective of this study was to hybridize these two species with the intention of combining the cold hardiness of H. arborescens with the flower color of H. involucrata. Over 150 reciprocal crosses were made between H. involucrata and H. arborescens ‘Dardom’ (White Dome®). Viable seed were obtained only when H. arborescens was used as the maternal parent. Of the more than 500 seed obtained, 36 germinated but only eight plants remain alive. Hybridity was verified using RAPD markers. The hybrids vary in size, but leaf shape is consistent among progeny and is intermediate in appearance between parents. These are the first confirmed Hydrangea interspecific hybrids to be obtained without the use of embryo rescue and to involve H. involucrata as a parent. Work with the H. arborescens x H. involucrata hybrids will continue in an effort to develop cold hardy hydrangeas with blue flower coloration.