1. US Department of Agriculture, Agricultural Research Service, North Central Regional Plant Introduction Station, 1305 State Avenue, Ames, IA 50014, USA
2. US Department of Agriculture, Agricultural Research Service, US National Arboretum, Otis L. Floyd Nursery Research Center, 472 Cadillac Lane, McMinnville, TN 37110, USA
3. Department of Horticultural Science, University of Minnesota, Alderman Hall, 1970 Folwell Avenue, Saint Paul, MN 55108, USA
4. Department of Environmental Horticulture, University of Florida, Tropical Research and Education Center, 18905 SW 280th Street, Homestead, FL 33031, USA