Submitted to: Southern Nursery Association Research Conference
Publication Type: Proceedings
Publication Acceptance Date: August 20, 2004
Publication Date: December 13, 2004
Citation: Reed, S.M. 2004. Floral characteristics of a Hydrangea macrophylla x H. paniculata hybrid. Proceedings of the Southern Nursery Association Research Conference. 49:580-582. Interpretive Summary: The genus Hydrangea contains several species that are widely cultivated as ornamentals. New, unique forms of these popular shrubs could be developed by hybridizing species with complementary traits. A hybrid between the bigleaf hydrangea, which has blue or pink flowers, and the panicle hydrangea, which is very cold hardy, were produced a few yeasr ago. One of these hybrids flowered for the first time recently. This report describes the inflorescence of that hybrid and efforts to utilize it in a breeding program. Inflorescences are large (6 inches in diameter) and similar to shape to the mophead-type inflorescence of bigleaf hydrangea. Flower color is white, aging to pale green. The hybrid was not fertile and thus could not be hybridized to either parental species. Results of this study indicate that species other than H. macrophylla need to be investigated as sources of flower color for future interspecific breeding projects in this genus.
Technical Abstract: The genus Hydrangea contains several species that are widely cultivated as ornamentals. While interspecific hybridization provides an opportunity to develop new forms of Hydrangea with unique combinations of superior traits, it has proven very difficult to recover wide hybrids between H. macrophylla and other members of the genus. Several H. macrophylla × H. paniculata hybrids were obtained using embryo rescue, but most died prior to reaching maturity. This report describes the inflorescence and flowers of the sole H. macrophylla × H. paniculata hybrid that has flowered, along with attempts to utilize this plant in backcrosses to parental species. The inflorescence is a corymb, with a diameter of approximately 15 cm, consisting of a combination of large, showy and small, inconspicuous flowers. On most inflorescences, the showy flowers completely cover the surface of the inflorescence while the inconspicuous flowers are located on the interior. This produces an appearance similar to that of the mophead-type H. macrophylla inflorescence. Bracts are creamy-white in color, aging to pale green. Anthers are present as petaloid structures and produce no pollen. Attempts to backcross the hybrid, using it as the maternal plant, to several cultivars of H. macrophylla and H. paniculata were not successful. Alternatives to H. macrophylla are being investigated as sources of flower color for future interspecific hybridization projects in this genus.