US National Arboretum


Floral and Nursery Plants Research Unit

Dr. Sandra Reed

Research Geneticist
{McMinnville, TN}


CRIS Project Title:  
Genetics, Breeding, and Improved Production Efficiency of Nursery Crops

Conducts research on breeding and genetics of Hydrangea, Clethra, Styrax and Cornus to develop improved cultivars.  Emphasis of breeding program is to develop new cultivars with resistance to diseases and insects, tolerance to environmental stress and superior ornamental qualities.  Both intraspecific and wide hybridizations are utilized, with embryo rescue being employed when necessary to secure wide hybrids.  Pollination biology, inheritance and cytogenetic studies are conducted in conjunction with the breeding projects.

One of the goals of the hydrangea breeding project is to combine cold hardiness and flower color.  We have produced two interspecific hybrids (Hydrangea macrophylla × H. paniculata and H. arborescens × H. involucrata) for use in this project.  Both involve one species with colored flowers and another with cold hardiness.  We are also using an intraspecific approach to this problem.  Controlled pollinations between reflowering (remontant) bigleaf hydrangea (H. macrophylla) cultivars, such as ‘Endless Summer’, ‘Penny Mac’ and ‘Oak Hill’, and cultivars with mildew resistance and a range of ornamental traits have been made.  Several seedlings that flower on current year’s growth have resulted from these pollinations and are undergoing evaluation.
Oakleaf hydrangeas (H. quercifolia) with compact plant form and large, upright inflorescences have been produced from controlled pollinations.  Five of these selections are being tested in various regions of the country.  A compact panicle hydrangea (H. paniculata) is also being evaluated.  Unlike standard cultivars of these two species, the compact selections will be suitable for use small residential landscapes. 

An intergeneric hybrid between Hydrangea macrophylla and Dichroa febrifuga has been produced.  Dichroa febrifuga has metallic blue fruit that persists throughout winter.  Incorporation of this trait into H. macrophylla would increase the winter appeal of this species.

A hybrid between Clethra alnifolia and C. pringlei was developed with the goal of combining cold hardiness and adaptability from C. alnifolia with ornamental foliage of C. pringlei.  The hybrid is intermediate in appearance between the two parents and has foliage that flushes red.  A number of variegated plants have been obtained from advanced generations derived from this hybrid, and are being evaluated for commercial potential. Styrax japonicus (Japanese snowbell) is a small ornamental tree that produces fragrant flowers in late spring to early summer.  Despite its ornamental merit, this species is under-utilized in the U.S., primarily because it is subject to damage from late spring frosts.  We selected 28 plants that broke dormancy approximately 3 weeks later than standard cultivars, which allowed them to escape spring freeze damage.  Four of these are currently being evaluated for release as cultivars.

Breeding programs in Hydrangea, Clethra, Styrax and Cornus will continue.  Wide hybrids will be evaluated for commercial merit.  Fertile hybrids will be intercrossed and/or backcrossed to parental species.  Additional intraspecific and wide hybridizations will be made.  Data will be collected from H. macrophylla hybrid populations on inheritance of inflorescence form, powdery mildew resistance and remontant flowering habit.  Data will be collected from cooperators on performance of 15 selections that are currently being evaluated in various parts of the country.  If information received on the performance of these selections is favorable, they will be released as cultivars.


Peer reviewed publications
1999.  Reed, S.M.  Development of a labor-efficient hand pollination procedure for flowering dogwood.  J. Environ. Hort. 17: 92-94.

2000.  Craddock, J.H., S.M. Reed, S.E. Schlarbaum, and R.J. Sauve.  Storage of flowering dogwood (Cornus florida L.) pollen.  HortScience 35:108-109.

2000.  Reed, S.M.  Compatibility studies in Hydrangea.  J. Environ. Hort. 18:29-33.

2000.  Reed, S.M.  Development of an in ovolo embryo culture procedure for Hydrangea.  J. Environ. Hort. 18:34-39.

2001.  Reed, S.M., G.L. Riedel, M.R. Pooler.  Verification and establishment of Hydrangea macrophylla 'Kardinal' × H. paniculata 'Brussels Lace' interspecific hybrids.  J. Environ. Hort. 19:85-88.

2002.  Reed, S.M., Y. Joung, M.S. Roh.  Interspecific hybridization in Clethra.  HortScience 37:393-397.

2002.  Reed, S.M.  Flowering performance of 21 Hydrangea macrophylla cultivars.  J. Environ. Hort. 20:155-160.

2003.  Reed, S. M.  Self-fertility and time of stigma receptivity in Styrax japonicum.  HortScience 38:429-431.

2004.  Reed, S.M.  Self-incompatibility and time of stigma receptivity in two species of Hydrangea.  HortScience. 39:312-315.

2004.  Reed, S.M.  Self-incompatibility in Cornus florida. HortScience. 39:335-338.

2005.  Reed, S.M.  Pollination biology of Hydrangea macrophylla.  HortScience 40:335-338.

2005.  Reed, S.M.  Cytological analysis of a Clethra alnifolia ‘Hokie Pink’ × C. pringlei hybrid.  HortScience 40:339-342.

2005.  Reed, S.M.  Effect of storage temperature and seed moisture on germination of stored flowering dogwood seed.  J. Environ. Hort. 23:29-32.

2005.  Reed, S.M.  Japanese snowbell exhibits variability for time of vegetative budbreak and susceptibility to spring freeze damage.  HortScience 40:542-545.

2006.  Jones, K.D. and S.M. Reed.  Production and verification of Hydrangea arborescens ‘Dardom’ × H. involucrata hybrids.  HortScience (in press).

2006.  Reed, S.M.  Pollination biology of Clethra alnifolia.  HortScience (in press).

2006.  Pounders, C., S.M. Reed and M.R. Pooler.  Comparison of self- and outcrossing on pollen tube growth, seed development, and germination in crapemyrtle.  HortScience (in press.)

Non-peer reviewed publications:
1996.  Reed, S.M., J.H. Craddock, S. Schlaurbaum, and R. Sauve. Storage of dogwood (Cornus florida) pollen.  Proc. Southern Nursery Assoc. Res. Conf. 41:355-358.

1998.  Reed, S.M.  Prospects for hybridization of Hydrangea macrophylla and H. paniculata.  Proc. Southern Nursery Assoc. Res. Conf. 43:324-326.

1998.  Reed, S.M. Effect of timing and frequency of controlled pollinations on seed set in flowering dogwood.  Proc. Southern Nursery Assoc. Res. Conf. 43:347-349.

1999.  Reed, S.M.  Breeding for cold hardiness in Hydrangea.  Landscape Plant News 10:3-5.

1999.  Reed, S.M.  Embryo rescue in Hydrangea.  Proc. Southern Nursery Assoc. Res. Conf. 44:373-375.

2000.  Reed, S.M.  Hydrangea macrophylla cold hardiness evaluation.  Proc. Southern Nursery Assoc. Res. Conf. 45:401-404.

2001.  Reed. S.M.  Hybridization of Clethra alnifolia and C. pringlei.  Proc. Southern Nursery Assoc. Res. Conf. 46:407-410.

2001.  Reed, S.M.  Hydrangeas for the future.  Proc. International Plant Propagators Society 51:90-94.

2002.  Reed, S.M.  Japanese snowbell (Styrax) - A great small tree for suburban landscapes.  Tennessee Green Times. 3:33-34.

2002.  Reed,.S.M. Clethra alnifolia × C. pringlei - A promising new ornamental.  Landscape Plant News.  13:3-4.

2003.  Reed, S.M.  Self-incompatibility in Hydrangea paniculata and H. quercifolia.  Proc. Southern Nursery Assoc. Res. Conf. 48: 477-479.

2004.  Reed, S.M.  Floral characteristics of a Hydrangea macrophylla × H. paniculata hybrid.  Proc. Southern Nursery Assoc. Res. Conf. 29:580-582.

2005.  Jones, K.D. and S.M. Reed.  Recent developments in Hydrangea interspecific hybridization.  Proc. Southern Nursery Assoc. Res. Conf. 50:643-645.

2005.  Reed, S.M.  Haploid cultures. In: Plant Development and Biotechnology (ed. R.N. Trigiano and D.J. Gray). CRC Press, Boca Raton. pp. 225-234.

2005.  Reed, S.M.  Embryo rescue. In: Plant Development and Biotechnology (ed. R.N. Trigiano and D.J. Gray). CRC Press, Boca Raton. pp. 235-239.

2005.  Reed, S.M.  Stabilizing dogwood seed supply through proper storage of excess seed.  Proc. Southern Nursery Assoc. Res. Conf.  50: 417-419.

2005.  Rinehart, T.A., Scheffler, B. and S.M. Reed.  Estimating genetic diversity within the Hydrangea genus using molecular markers.  Proc. Southern Nursery Assoc. Res. Conf. 50:656-659.

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