University of Minnesota
College of Food, Agricultural and Natural Resource Sciences
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Department of Horticultural Science

Stan Hokanson

Stan HokansonWoody Plant Breeding
Department of Horticultural Science


70% Research, 30% Teaching


Research Interests

The Woody Landscape Plant Breeding project at the University of Minnesota has been in existence for 59 years. In that time the project has been responsible for the release of 54 woody plant cultivars. The project’s overarching objective continues to be the development of new and improved trees and shrubs for USDA plant hardiness zone 4 landscapes. The approach to this objective involves a systematic process of traditional breeding, selection and evaluation. For the more developed breeding projects, such as deciduous azalea and weigela, the process assumes the form of recurrent phenotypic selection, in which meritorious individuals from each generation are selected for cultivar potential and/or used as parents in subsequent generations. These selections are based on data collected over multiple years. For new breeding initiatives, such as ongoing efforts with Korean maple (Acer pseudosieboldianum) and American smoketree (Cotinus obovatus) the process begins with a germplasm evaluation of seedlings originating from the northern-most location we can identify or a commercial source with good passport information.

Figure 1. Korean maple (Acer pseudosieboldianum) x Japanese maple (A. palmatum) seedlings.

Such evaluations provide a sense for the taxa’s range of potential qualities, and allow us to begin selecting parents for the breeding process. 

In recent years, plant patenting, product branding, and marketing activities have intensified in the landscape nursery industry. Many new players are now engaged in the new plant development process. This transformation has given reason to pause and consider; what is a public, academic institutions unique role in the system? One of the universities primary roles has always been to generate and disseminate new knowledge. As such, the merits of new cultivars released from a university program should be based on data. Another critical role we can play is to generate new knowledge regarding the genetic and physiological processes the control important traits in woody landscape plants. In our program, such projects are often undertaken by graduate students as thesis and dissertation projects. The results are typically published in peer-reviewed journals and/or presented at national meetings. 

Teaching/Advising Responsibilities

Current Graduate Student Research

Will Kusch, a Ph.D. candidate, co-advised by Dr. Ulrike Tschirner in the Department of Bioproducts and Biosystems Engineering, is conducting an evaluation of Alnus germplasm for its potential as a source biofuel in the upper Midwest. The germplasm is being evaluated for survival and growth in five Minnesota locations. He is evaluating wood samples in the laboratory for several key structural and chemistry properties.

Alex Susko, an M.S. candidate, co-advised by Dr. Jim Bradeen in the department of Plant Pathology, is undertaking a project to collect and begin the evaluation process for several native deciduous azalea (Rhododendron subg. Pentanthra) species in the northeastern U.S. The project will involve a n assessment of the genetic diversity and structuring of that diversity in natural populations of the species. 


Zlesak, D.C., K. Zuzek, and S.C. Hokanson. 2013. Gender Inheritance and Identification of Male Sterility Gene RSMS1 in Intra- and Inter-specific Crosses of Dioecious Rosa setigera Michaux. Floriculture and Ornamental Biotechnology. 7:60-64.

Hokanson, S.C. and S. McNamara. 2013. Can’t Always Get What We Want! Finding and Creating Cold for Hardiness Screening at the University of Minnesota. Acta Horticulturae. (In press)

Kusch, W., U. Tschirner, S. McNamara, A.J. David, D. Current, and S.C. Hokanson. 2013. An Evaluation of Alnus (Alder) Germplasm in Five Diverse Nonagricultural Environments in Minnesota (U.S.A.). Acta Horticulturae. (In press)

Krebs, S.L., M.C. Long* and S.C. Hokanson. 2011. A garden survey of powdery mildew disease on deciduous azalea species and cultivars. Journal American Rhododendron Society 65:90-97.

Zlesak, D.C., V.M. Whitaker*, S. George and S.C. Hokanson. 2010. Evaluation of roses from the EarthKind® Trials: Black Spot (Diplocarpon rosae Wolf.) Resistance and Ploidy. HortScience 45:1-9.

Wadl, P.A., X. Wang, J.K. Moulton, S.C. Hokanson, J.A. Skinner, T.A. Rinehart, S.M. Reed, V.R. Pantalone and R.N. Trigiano. 2010. Transfer of Flowering and Kousa Dogwood Simple Sequence Repeats (SSRs) to Selected Cornus (Cornaceae) Species. American Journal of Horticultural Science 135:279-288.

Meyer, M.H., S.C. Hokanson, S. Galatowitsch, and J.J. Luby. 2010. Public Gardens: Fulfilling the University’s Research Mission. HortTechnology 20:522-527.

Long, M.C.*, S.K. Krebs, and S.C. Hokanson. 2010. Field and Growth Chamber Evaluation of Powdery Mildew Disease on Deciduous Azaleas. HortScience 45:784-789.

Whitaker, V.M.*, T. Debener, A.V. Roberts and S.C. Hokanson. 2010. Unified nomenclature for an international collection of Diplocarpon rosae: races and a standard host differential set. Plant Pathology 59:745-752.

Whitaker, V.M.*, J.M. Bradeen, T. Debener, A. Biber and S.C. Hokanson. 2010. Rdr3, a novel locus conferring black spot disease resistance in rose: genetic analysis, LRR profiling, and SCAR marker development. ORIGINAL REPORT Theoretical and Applied Genetics 120:573-585.

McNamara, S.* and S.C. Hokanson. 2010. Cold Hardiness of Weigela (Weigela florida Bunge) Cultivars. Journal of Environmental Horticulture 28:35-40.

Hokanson, S.C. 2010. Lights in the Land of 10,000 Lakes. Pgs. 22-32. In: Royal Horticultural Society Yearbook of Rhododendrons, Camellias, and Magnolias.

Whitaker, V.M.* and S.C. Hokanson. 2009. Partial resistance to black spot disease in diploid and tetraploid roses: general combining ability and implications for breeding and selection. Euphytica 169:421-429.

Whitaker, V.M.* and S.C. Hokanson. 2009. Breeding Roses for Disease Resistance. Plant Breeding Reviews, 2009, Vol. 31. Pgs. 277-324. Jules Janick (ed.) John Wiley and Sons, New York.

Whitaker, V.M.*, K. Zuzek*, and S.C. Hokanson. 2007. Resistance of 12 rose genotypes to 14 isolates of Diplocarpon rosae Wolf (rose blackspot) collected from eastern North America. Plant Breeding 126:83-88.

Whitaker, V.M.*, J.M. Bradeen, and S.C. Hokanson. 2007. Distribution of rose blackspot (Diplocarpon rosae Wolf) genetic diversity in eastern North America using AFLP and implications for resistance screening Journal of the American Society for Horticultural Science 132:534-540.

Whitaker, V.M.*, K. Zuzek*, J.M. Bradeen, and S.C. Hokanson. 2007. Culturing and long-term storage of virulent races of the rose blackspot pathogen Diplocarpon rosae Wolf. Acta Horticulturae 751:199-205.

Zuzek, K.* and S.C. Hokanson. 2007. Shrub rose breeding at the University of Minnesota. Acta Horticulturae 751:291-298.

Zlesak, D., K. Zuzek*, and S.C. Hokanson. 2007. Rose pollen viability over time at varying storage temperatures. Acta Horticulturae 751:337-343. 

Book chapters

Whitaker, V.M. and S.C. Hokanson.  2009. Breeding Roses for Disease Resistance. p. 277-324. In:  J. Janick (ed.). Plant Breeding Reviews, Vol. 31. John Wiley and Sons, New York.

Forsline, P.L., H. S. Aldwinckle, E. E. Dickson, J. J. Luby, and S.C. Hokanson.  2003. Collection, Maintenance, Characterization, and Utilization of Wild Apples of Central Asia. p. 1-62. In: J. Janick (ed.). Horticultural Reviews, Volume 29, Wild Apple and Fruit Trees of Central Asia. John Wiley and Sons, New York.

Hokanson, S.C. and J.L. Maas.  2001. Strawberry biotechnology, p. 139-180. In:  J. Janick (ed.). Plant Breeding Reviews, Vol. 21. John Wiley and Sons, New York.


258 Alderman Hall
1970 Folwell Avenue
St. Paul, MN 55108

Phone: 612.624.1203