In 1984 and 1985, 21 landscape plant introductions from northern Japan were distributed for testing in the NC-7 Regional Ornamental Plant Trials. Seventeen of these introductions were evaluated for 10 years at six to ten sites representing a cross-section of growing conditions in the north central United States. For these 17 introductions, first-year survival averaged 60%; however, by year 10, fewer than 20% of the original 425 plants were alive. Based on these evaluations, the populations could be divided into four groups. One population of Rosa rugosa was adapted to most trial sites; two populations (Alnus hirsuta and Lonicera chrysantha) were adapted to some sites; three populations were of poorly adapted dieback shrubs, and the remaining 11 populations included a diverse set of trees and shrubs unadapted to any, or nearly any, trial site. Temperature and moisture data from Japan and from trial sites were used to examine relationships between plant adaptation and climate. Statistically significant, multiple-regression models were calculated to describe the functional relationships between temperature and moisture conditions and plant adaptation at the various trial sites. Our models predict that plants from northern Japan are best adapted to sites in the northeastern United States where moisture surpluses exceed those typically found in the north central United States. These models also suggest criteria to evaluate sites throughout northeastern Asia for future exploration.
Journal Paper No. J-17596 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 1018, and supported by Hatch Act and State of Iowa funds. The authors thank the Chicago Botanic Garden and the Martin Foundation for their financial support of the initial exploration and Harrison Flint, William Graves, Paul Meyer, and George Ware for useful critiques of this report.
2Horticulturist, USDA-Agricultural Research Service, Ames, IA 50011.
3Research Plot Coordinator, Univ. of Minnesota, Southern Experiment Station, 35838 120th St., Waseca, MN 56093.
4Professor, North Dakota State Univ., Dept, of Plant Sciences, Box 5051, Fargo, ND 58105.
5Assistant Professor, Iowa State Univ., Dept, of Horticulture, Ames, IA 50011.
6Associate Professor, Univ. of Illinois, Dept, of Natural Resources and Environmental Sciences, 1201 S. Dorner Drive, Urbana, IL 61801.
7Agricultural Science Research Technician, USDA-Agricultural Research Service, Ames, IA 50011.
8Research Horticulturist, Kansas State Univ., Horticulture Research Center, 1901 East 95th St. South, Wichita, KS 67233.
9Associate Professor, Univ. of Nebraska, Dept, of Horticulture, 377 Plant Sciences Bldg., Lincoln, NE 68583.
10Horticulture Research Plot Coordinator, Univ. of Minnesota, West Central Experiment Station, Box 471, Morris, MN 56267.
11Research Horticulturist, Minnesota Landscape Arboretum, Box 39, Chanhassen, MN 55317.
12Associate Professor, Michigan State Univ., Dept, of Horticulture, Plant & Soil Science Bldg., East Lansing, MI 48824.
13Horticulturist, The Holden Arboretum, 9500 Sperry Road, Kirtland, OH 44094.
14Professor, Univ. of Minnesota, North Central Experiment Station, 1861 Highway 169 East, Grand Rapids, MN 55744.