1. 1Department of Plant Sciences, North Dakota State University, NDSU Dept. 7670, P.O. Box 6050, Fargo, ND 58108
2. 2Department of Horticultural Science, University of Minnesota, 1970 Folwell Avenue, 305 Alderman Hall, St. Paul, MN 55108
3. 3Department of Horticultural Science, University of Minnesota, MN Landscape Arboretum, 1970 Folwell Avenue, 305 Alderman, Hall, St. Paul, MN 55108