Ornamental Plant Breeding Program

Oregon snowflake bred at OSU


Why Breed Onamentals at OSU?

New to OSU, this dynamic and diverse breeding program includes 15 genera and encompasses various perennial crops, native, and non-native shrubs, shade trees, and flowering plants. It strives to support the economically important Oregon industry that is number one in shade trees, conifers, and flowering trees production. Oregon ranks 3rd in the nation in the production of nursery stock, providing most of the trees for the eastern United States. In 2011, Oregon produced 7% of the nation’s nursery stock from their ecologically sound nurseries for a farmgate value of nearly 742 million dollars.

The OSU Ornamental research program involves several areas of ornamental plant breeding and cultivar development. Of primary interest is the development of sterile forms of nonnative species that are of economic importance to Oregon growers to prevent escape from cultivation. Primary techniques to achieve sterility/reduced fertility include develoment of triploids using ploidy manipulation, as well as mutagenesis by exposing seeds or meristems to physical and chemical mutagens.

Another area of focus is to identify cultivars or selections that have increased insect and disease resistance. The program conducts basic research in traditional genetics, cytogenetics, and molecular cytogenetics to support the applied breeding program with the goal of developing plants that are attractive to consumers and easy for growers to produce.


To develop aesthetic plants that meet specific needs, such as sterility, disease and insect resistance, improved landscape performance, and novel ornamental traits which can be propagated easily under nursery conditions while maintaining vigor.

Current Research Projects

  1. The development of sterile forms of nonnative invasive species that are of economic importance to Oregon growers.
  2. To identify cultivars or selections that have increased insect and disease resistance.
  3. Genera Specific Goals:
    • Acer - Sterility, ploidy manipulation
    • Berberis - Sterility, thornlessness, and ploidy manipulation
    • Cercidiphyllum - Weeping form with purple leaves, infraspecific hybridization
    • Cotoneaster- Sterility, disease resistance, interspecific interploidy crosses
    • Galtonia - Compact, mutagenesis (EMS)
    • Hibiscus - Sterile and compact, infraspecific hybridization, flow cytometry
    • Hydrangea - Compact, large flowers, thicker stems, ploidy manipulation
    • Malus - Sterility, ploidy manipulation
    • Penstemon - improve garden tolerance to thrive in increased water environments, interspecific hybridization
    • Philadelphus - fragrance, adaptability, inflorescence length, interspecific hybridization
    • Prunus  - Sterility; shot holt disease resistance, interspecific hybridization, ploidy manipulation, mutagenesis (gamma)
    • Ribes - Improved form and combination of traits (color and cut leaf), mutagenesis (EMS)
    • Sarcococca - Variation in form, leaf, flower, and fruit, mutagenesis (EMS)
    • Syringa - Disease resistance, fragrance, form, intersectional hybridization
    • Thuja - Non-winter browning, mite resistance, ploidy manipulation
    • Nyssa - Weeping and other improved selections from campus
    • Vaccinium - Evergreen compact, larger fruit, sweeter fruit

Graduate Student Expectations

PI statement of expectations for grad students:
  1. Conduct research independently while contributing to the overall breeding program by supporting lab, greenhouse, and field activities.
  2. Willingness to be creative and explore alternative ways to address questions.
  3. Masters students are expected to publish at least one journal article; Ph.D. students are expected to publish at least three journal articles.
  4. Presentations at grower field days, academic conferences, and seminars.

Breeding Methods

  1. Ploidy manipulation:
    • Identification and classification with flow cytometry
    • Induced polyploids and backcrossing using FCM to develop sterile triploid Norway maple, Cherry laurel, Japanese barberry, and malus.
    • Polyploidy in arborvitae to develop non-winter browning forms and increase insect resistance.
  2. Interspecific hybridization: Interspecific hybridization among Cherry laurels to develop disease resistant and sterile forms, Philadelphus, Penstemon, Syringa
  3. Mutagenesis (EMS and gamma): Mutation breeding in Sarcococca confusa, Ribes sanguineum, Galtonia
  4. Developing disease resistant and reblooming lilacs.


  • Oregon Association of Nurseries
  • J. Frank Schmidt Family Charitable Foundation
  • Agricultural Research Foundation
  • USDA
  • American Penstemen Society
  • Bailey Nurseries, Inc.
  • Heritage Seedlings
  • Fall Creek Nursery


Within Oregon State University
  • Todd Einhorn - Department of Horticulture
  • Virginia Stockwell - Department of Botany and Plant Pathology
  • Statewide
    1. Oregon Department of Agriculture
    2. Hoyt Arboretum, Portland, Oregon
    3. Bailey Nurseries Inc.
    4. Blue Heron Farms
    5. Monrovia Nursery
    6. Heritage Seedlings
    7. Carlton Plants
    8. Blooming Nursery
    9. J. Frank Schmidt and Sons
  • National
    1. Atlanta Botanical Garden, Atlanta, Georgia
    2. University of Georgia: Department of Crop and Soil Science
    3. Virginia Tech: Department of Crop, Soil and Environmental Sciences
    4. USDA- ARS

Past and Present Graduate Student Projects

1. Joseph Rothleutner- past Masters student

  • Documented the genome sizes and chromosome numbers of species of Cotoneaster for which these data was previously unknown and researched the variation in fire blight resistance among species.
  • Currently a Tree Improvement Specialist at Morton Arboretum, Chicago, IL

2. Jason Lattier -  Ph.D. student

  • Current research focus is on breeding, cytogenetics, and micropropagation of ornamental nursery crops.
  • Recently completed at B.S. in Horticultural Science, a B.S. in Botany, and an M.S. in Horticultural Science at NC State University.   

3. Justin Schulze - M.S. Student

  • Assessing the carbon budget of 22x and 44x Prunus laurocerasus 'Otto Luyken' in container production
  • In vivo polyploidization of Prunus lusitanica

4. Kim Shearer-Lattier - M.S. Student

  • Genome size and ploidy level survey in Acer
  • Interspecific hybridization in Penstemon to improve adaptibility to cultivation.

Mara Friddle joined the ornamental breeding program at OSU as a lab technician in 2010. Mara helps with daily plant maintenance for making crosses, testing ploidy levels with a flow cytometer, cleaning, weeding, data collection, and ensuring all current projects are moving forward. She received her Bachelor’s Degree from Colorado State University in Horticulture with a concentration on nursery and landscape management. Prior to joining OSU, Mara worked for 8 years as canola breeding technician.

Economic Significance

In 2011, Nursery and Greenhouse crops were ranked the top commodity in Oregon with a farmgate economic value of $742 million dollars. It is estimated in 2013 that the economic value will exceed $1 billion dollars as it has been in previous years.  Oregon is central to the ornamental industry, exporting ornamental and nursery plants all over the United States.

Due to the high diversity of the ornamental plant industry, a large number of plants are studied to produce economically important and ecologically sound varieties that are disease and pest resistant, heat tolerant, and non-invasive so they do not impede native landscapes. Newly released plants with these traits have health and safety benefits, lower the economic cost to homeowners and gardeners, and benefit the ornamental plant industry in the United States.

Staff Profiles

Jennifer Kling - Professor/Senior Research, is the solo project lead for the OSU meadowfoam breeding project. Dr. Kling holds a Ph.D. in Genetics with a minor in Statistics from North Carolina State University. Prior to her work at OSU, she was a maize breeder at the International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria. Jennifer is also renowned on the OSU campus for her expertise in experimental design, and statistics related to plant breeding and genetics.

Publications and Varieties Released

Cultivar Releases


  • Ribes sanguineum ‘Oregon Snowflake’ PPAF


Refereed Journal Articles









  • Contreras, R.N. and T.G. Ranney. 2008. New opportunities for breeding fragrant rhododendrons. J. Amer. Rhododendron Soc. 62(4):201-202.



Conference Proceedings

Lattier, J.D. and R.N. Contreras.  2014.  Hybridization Studies in Lilacs (Syringa L.).  Proc. 59th Ann. SNA Res. Conf. 59:229-234.

Contreras, R.N.  2014.  Ornamental Plant Breeding at Oregon State University.  Combined Proceedings of the International Plant Propagators' Society 63. <http://www.pubhort.org/members/ippsue?session=>

Contreras, R.N., J. Rothleutner, and V. Stockwell.  2014.  Breeding for fire blight resistance and sterility in Cotoneaster.  Proceedings of the 13th International Workshop on Fire Blight. Acta Hort. 1056:221-223.

Contreras, R.N., M. Friddle, and J.D. Lattier.  2013.  Relative fertility and ploidy levels of selected rose of sharon cultivars.  Proc. 58th Ann. SNA Res. Conf.  58:232-236.

Rothleutner, J.J., R.N. Contreras, and V. Stockwell.  2012.  Evaluation of fire blight resistance of 31 species of Cotoneaster.  Proc. 57th Ann. SNA Res. Conf. 57:276-278.

Contreras, R.N. and J.M. Ruter. 2010. Induced polyploidy in Japanese cedar. Proc. 55th Ann. SNA Res. Conf. 55:25-29.

Contreras, R.N. and J.M. Ruter. 2008. Preliminary efforts to induce polyploidy in Cryptomeria japonica. Proc. 53rd Ann. SNA Res. Conf. 53:159-161.

Contreras, R.N. and J.M. Ruter. 2007. New Callicarpa species with breeding potential. Proc. 52nd Ann. SNA Res. Conf. 52:327-329.

Contreras, R.N., T.G. Ranney, S.P. Tallury and S.R. Milla. 2005. Using molecular  markers to investigate parentage of azaleodendron hybrids. 2005. Proc. 50th Ann. SNA Res. Conf. 50:632-635.

Contreras, R.N. and T.G. Ranney. 2004. New opportunities for breeding allopolyploid azaleodendrons. Proc. 49th Ann. SNA Res. Conf. 49:552-554.


Abstracts and Posters

Lattier, J.D. and R.N. Contreras.  2014.  Colorimetric phenotyping of tetraploid progeny exhibiting incomplete dominance for flower color.  Independent Plant Breeders Conference.  Grand Rapid, MI

Shearer-Lattier, K. and R.N. Contreras.  2014.  Non-targeted mutagenesis of Galtonia candicans by exposing seeds to EMS.  Independent Plant Breeders Conference.  Grand Rapid, MI, October 30 – November 2, 2014.

Contreras, R.N. and L. Meneghelli.  2013.  In Vitro Chromosome Doubling of Prunus laurocerasus ‘Otto Luyken’.  Proc. 109th Ann. Amer. Soc. Hort. Sci. Res. Conf.  HortScience (Accepted) (Abstr.)

Schwartz, B.M., R.N. Contreras, W.W. Hanna, and S.A. Jackson.  2013.  Manipulating the Chromosome Number of Zoysiagrass.  ASA-CSSA-SSSA Abstracts 2013. (Abstr.)

Schwartz, B.M., R.N. Contreras, K.R. Harris-Schultz, J.B. Peake, and P.L. Raymer.  2012.  Identification or Creation of a Putative Triploid Seashore Paspalum.  ASA-CSSA-SSSA Abstracts 2012. (Abstr.)

Rothleutner, J.J. and R.N. Contreras.  2012.  Variable Fire Blight Resistance Among 31 species of Cotoneaster.    Proc. 109th Ann. Amer. Soc. Hort. Sci. Res. Conf.  HortScience 47(9):S366 (Abstr.)

Einhorn, T., Gibeaut, D., Contreras, R.N., and Whiting, M.  2012. Polyploidy of cells in sweet cherry fruit.  Proc. 109th Ann. Amer. Soc. Hort. Sci. Res. Conf.  HortScience 47(9):S387 (Abstr.)

Gibeaut, D., R. Contreras, T. Einhorn, and M. Whiting.  2011.  Cropload affects the size, but not the number or polyploidy of cells in sweet cherry fruit. Washington State Horticultural Association 107th Annual Meeting, Wenatchee, WA, December 5-7, 2011.

Contreras, R.N., J.M. Ruter, J. Conner, Y. Zeng, and P. Ozias-Akins.  2011.  Interspecific hybridization in Tecoma Juss. (Bignoniaceae):  Confirmation of hybridity using GISH and morphology.  HortScience 46(9):S320. (Abstr.)

Rothleutner, J.J. and R.N. Contreras.  2011.  Genome size estimates for Cotoneaster spp.  HortScience 46(9):S386 (Abstr.)

Schwartz, B., K. Harris, R.N. Contreras, and W. Hanna. 2010. Colchicine-induced tetraploidy in centipedegrass. ASA-CSSA-SSSA Abstracts 2010 (in press). (Abstr.)

Contreras, R.N. 2010. Breeding methods to reduce the invasive potential of nursery crops. HortScience 45(8):S29 (Abstr.)

Contreras, R.N. and John M. Ruter. 2010. Fruit color in American beautyberry is controlled by a single gene. HortScience 45(8):S280 (Abstr.)

Contreras, R.N. and John M. Ruter. 2009. An oryzalin induced polyploidy from a hybrid of Hibiscus acetosella x H. radiatus(Malvaceae) exhibits reduced fertility and altered morphology. Proc. 106th Ann. Amer. Soc. Hort. Sci. Res. Conf. HortScience 44(4):1177.

Contreras, R.N. and John M. Ruter. 2008. Evaluation of Callicarpa spp. for ornamental potential. Proc. 105th Ann. Amer. Soc. Hort. Sci. Res. Conf. HortScience 43(4):1266.

Contreras, R.N. and Thomas G. Ranney. 2006. Reproductive behavior of diploid and allotetraploid azaleodendrons. Proc. 66th Ann. SR-ASHS Res. Conf. HortScience 40(3):497-498.


Trade Publications

Shearer Lattier, K. and R.N. Contreras.  2015.  Penstemon breeding in the Willamette Valley:  A lesson in flexibility.  Bulletin of the American Pestemon Society (Accepted).

Contreras, R.N. and J.D. Lattier.  2014.  Improving a garden classic.  Digger, August:47-50.

Contreras, R.N. and M. Horn. 2014.  Breeding to improve garden performance of Penstemon in the Willamette Valley:  early stages.  Bulletin of the American Pestemon Society 73:68-72.

Contreras, R.N. and G. McAninch.  2013.  Back from the ban: new Buddleja cultivars receive exemption under ODA amendment.  Digger, October:33-36.

Contreras, R.N. and T. Rinehart.  2012.  An express route to perfection.  Digger, August: 47-50.

Rothleutner, J.J. and R.N. Contreras. 2012. Celebrating Cotoneaster. Digger, January:33-36.

Contreras, R.N. and J.S. Owen. 2011. The Economy of Water. Digger, August:139-144.

Contreras, R.N. 2011. Bred for success. Digger March:41-45.

Contreras, R.N. 2010. Bridging the gap: A new partnership between Oregon State University and LPDC designed to continue cultivar development. Landscape Plant News

Contreras, R.N. and J.M. Ruter. 2010. Developing an evergreen, evergreen: Winter browning in Japanese cedar. Amer. Conifer Soc. Quarterly J. 27(1):19-23.

Contreras, R.N. and John M. Ruter. 2009. Callicarpa evaluation and breeding at The University of Georgia Tifton Campus. Landscape Plant News 20(2):3-5.

Contreras, R.N. and John M. Ruter. 2008. Evaluation of Callicarpa spp. for utilization in a breeding program. Georgia Green Industry Association Journal. May/June 32-33.