More information on these accessions and their performance can be found in the article, "Performance of Landscape Plants from Northern Japan in the North Central United States" by M. Widrlechner et al in the Journal of Environmental Horticulture 16(1):27-32, March 1998. In part, the models used in this article "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."
Alnus hirsuta (Spach.) Rupr. Manchurian alder. These collections were made from small trees (to 7.6 m in height) with lustrous, bright green leaves. The species is similar to the speckled alder, but the leaves are more strongly lobed. Three PI numbered accessions were offered for trial:
PI 479293 (NA 51157) was collected from the Akkeshi Prefectural Forest, Hokkaido, 43 06' N. 145 00' E., minimum temperature -20C. Probable hardiness USDA Zone 5a.
PI 479294 (NA 51215) was collected from the Tokyo University Arboretum, Furano Forest, Yamabe, Furano-shi, Hokkaido, 43 14' N. 142 24' E., snow cover 2.5 m per annum. Seed was collected from one small, deciduous tree, 6 m tall, with lustrous green leaves above, glaucous beneath. Probable USDA hardiness Zone 5a.
PI 479295 (NA 51263) was collected from the Hokkaido University Tomakomai Experimental Forest, Hokkaido, 42 38' N. 141 39' E., minimum temperature -30C. Probable hardiness USDA Zone 5a.
Alnus hirsuta (Spach.) Rupr. Ames 23190. Manchurian alder. First identified as A. japonica (PI 479396 and NA 51160), this accession was recently re-identified as A. hirsuta. The collection was made from a hedge around a residence in Osonai, Hokkaido, 43 09' N. 145 04' E., minimum temperature -20C. Probable hardiness USDA Zone 6a.
Alnus pendula Matsum. PI 479302 (NA 51321). Japanese shrub alder. This collection was made from a low, spreading shrub (approx. 1.8 m in height), with dark brown, shining branches. The species can grow to be a small tree to 8 m. Pendula refers to the slender-stalked strobiles, not to pendulous branches. The collection location was made in Suiren Numa, Honshu, 40 37' N. 140 53' E., elevation 1005 m, minimum temperature -20C. Probable hardiness USDA Zone 6a.
Betula ermanii Cham. Erman birch. This medium-sized, densely branched tree is noted for its erect strobiles and peeling, light bark. Its inclusion in the trials was in part to be tested for insect resistance. Two PI numbered accessions were offered for trial:
PI 479318 (NA 51049) was collected from the Hokkaido University Teshio Forest at Kasai, 45 00' N. 141 58' E., minimum temperature -17C. Probable hardiness USDA Zone 6a.
PI 479320 (NA 51114) was collected from Rausu-cho, Hokkaido, 44 03' N. 145 10' E., minimum temperature -20C. Probable hardiness USDA Zone 6a.
Betula maximowicziana Regel. Monarch birch. This handsome birch is known for its large, cordate leaves and interesting gray bark. This species possesses complete resistance to bronze birch borer and tolerance to urban conditions. For more information consult P.C. Kozel and R.C. Smith, Horticulture 54(1); 36. 1975; and F.S. Santamour and F.G. Meyer, Amer. Nurseryman 145(12):7. Three PI's were offered for trial:
PI 479323 (NA 51052) was collected from the Hokkaido University Teshio Forest, 44 53' N. 141 55' E., minimum temperature -17 C. Probable hardiness USDA Zone 5b.
PI 479324 (NA 51174) was collected 3.2 km southeast of Lake Kusharo, Teshikagomachi, Hokkaido, 43 35' N. 144 26' E., minimum temperature -25C. Probable hardiness USDA Zone 5b.
PI 479325 (NA 51190) was collected along the northeast side of Lake Kusharo, Teshkaga-machi, Hokkaido, 43 36' N. 144 26' E., minimum temperature -25 C. Probable hardiness USDA Zone 5b.
Phellodendron amurense Rupr. PI 479512 (NA 51420). Amur cork-tree. This tree wis distinguished by its wide-spreading branches and corky, deeply fissured bark. It is becoming more available in the trade and this PI should be compared to commercial selections for such characteristics as hardiness and rom. This collection was made in Esash-machi, Hokkaido, by Dr. Katayose of the Hokkaido Forest Breeding Station. Probable hardiness USDA Zone 4.
Weigela hortensis (Sieb. & Zucc.) C.A. Mey. PI 479650 (NA 51344). Japanese weigela. This is a medium sized, deciduous shrub with arching branches and carmine flowers. This collection was made in Kansuizawa, Honshu, 40 39' N. 140 50' e., elevation 730 m, minimum temperature -20C. Probable hardiness USDA Zone 6a.