Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/1997
Publication Date: N/A
Interpretive Summary: The climates and soils of the north central U.S. limit the diversity of trees and shrubs that nurseries in the region can successfully produce and that perform well in the landscape. New plants from parts of the world with climates resembling those in the north central states, especially after such plants have undergone adequate testing, could expand the product diversity of local nurseries. This study, which reports on a long-term evaluation of 21 populations of woody plants from northern Japan at sites in the region, produced three findings with potentially favorable impacts for the nursery industry and for plant scientists studying the basis of woody plant adaptation. First, the evaluations identified two plants of potential merit: a Rugosa rose and a Manchurian alder. The rose was particularly well adapted throughout the region, and superior individual plants of this rose should be propagated and tested for possible release as a named variety. Second, mathematical models were developed to relate moisture and temperature data to patterns of plant survival in the north central U.S. These models indicated that most woody plants from northern Japan are poorly adapted to typical drought stress at the test sites, suggesting that, in general, northern Japan's maritime climate is a poor match for climates in the north central U.S. Finally, the results of this evaluation were used to produce a list of climatic conditions that can help locate promising sites in north eastern Asia for future plant exploration and collection. This can ultimately lead to new products for nurseries and increased diversity of well adapted trees and shrubs for the north central states.
Technical Abstract: 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 are suggest criteria to evaluate sites throughout northeastern Asia for future exploration.