Location: Floral and Nursery Plants Research Unit
Title: Breeding and propagating oakleaf hydrangeas Authors
Submitted to: International Plant Propagators Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 10, 2011
Publication Date: N/A
Interpretive Summary: An oakleaf hydrangea breeding program at the U.S. National Arboretum’s worksite in McMinnville, Tenn. was started in 1996 for the purpose of developing attractive, compact oakleaf hydrangea cultivars suitable for use in small residential gardens. This report describes the development of two new compact cultivars of oakleaf hydrangea along with techniques for propagating the species from seeds and cuttings. ‘Ruby Slippers’ and ‘Munchkin’ oakleaf hydrangeas were released by the U.S. National Arboretum in 2010. Both are compact forms with large, upright flower heads. ‘Munchkin’ is the smaller of the two, reaching only 3 feet tall after 9 years, while ‘Ruby Slippers’ grew to 3.5 feet in 7 years. The flowers of ‘Ruby Slippers’ turn a deep rose color at maturity, while those of ‘Munchkin’ turn medium pink. Both cultivars are well-suited for small residential landscapes. Seeds and cuttings were propagated in a greenhouse; both produced plants suitable for transplant to 3-gallon containers within a few months.
Technical Abstract: An oakleaf hydrangea breeding program at the U.S. National Arboretum’s worksite in McMinnville, Tenn. was started in 1996 for the purpose of developing attractive, compact oakleaf hydrangea cultivars suitable for use in small residential gardens. ‘Ruby Slippers’ and ‘Munchkin’ oakleaf hydrangeas were developed from this program and released in 2010. ‘Ruby Slippers’ grew to 3.5 feet high and 5 feet wide in 7 years. In early summer, it produces 9 – inch - long inflorescences that are held upright above the foliage. ‘Ruby Slippers’ flowers open white, but quickly turn pale pink and then deepen to deep rose color. ‘Munchkin’ is a bit smaller, reaching 3 feet tall and 4.5 feet wide after 9 years. It produces abundant, 6.5 – inch - long inflorescences that are also held upright above the foliage. ‘Munchkin’ flowers open white and gradually turn medium pink. For the oakleaf hydrangea breeding program, seeds obtained from pollinations were sown in shallow seed trays and germinated in a greenhouse. They were ready for transplant to the field or 3-gallon containers 5 months after being sown. Seedlings selected for superior characteristics were rooted from semi-hardwood cuttings that were propagated in a fog-filled greenhouse. Rooting occurred in 4 to 6 weeks, and rooted cuttings were overwintered in a cool greenhouse. The following spring they were ready for transplant to 3-gallon containers.