Why send two of the Arnold Arboretum’s staff members on a seed-collecting expedition to Japan and The Republic of Korea? The flora of the former country is about as well catalogued as that of any in the world; most of its outstanding ornamental woody plants are already in cultivation in the West; and several other American arboreta and botanic gardens have recently sponsored collecting expeditions to Japan.
These facts notwithstanding, there are several very good reasons why we embarked with enthusiasm and high expectations on September 1, 1977 for a six-week collecting trip marked by international goodwill and several botanical surprises. First, the Arnold Arboretum was the leader among American institutions in exploring the flora of temperate Asia, yet it had not sent an expedition since E. H. Wilson returned from Japan and Korea in 1918. The time was certainly due for the Arboretum to re-establish its contacts and interests in that part of the world. Second, many of Japan’s fine ornamentals are represented in Western horticulture by relatively few original collections—collections that often were made in warmer parts of the country and the resulting plants are not reliably hardy in the northern United States. Could not collections of these same plants from areas with more rigorous climates increase the hardiness range of some fine ornamentals? Third, collections from wild sources, with minimal chances of being hybrids, are valuable for botanical study. And finally, Korea has been largely neglected by American plant explorers, yet in its flora are many plants otherwise known only from China (at present still inaccessible to us) and its climate is in some places more rigorous than that of much of New England.
The first week and a half of collecting were spent on Hokkaido, where our itinerary had been largely arranged by Dr. Tadao Ui, Director of the Botanic Garden of the Faculty of Agriculture of Hokkaido University in Sapporo. We were accompanied by Dr. Katsuhiko Kondo of Hiroshima University, and received support from many Japanese officials. The northernmost of Japan’s four major islands, Hokkaido lies approximately between 41 and 45 degrees North Latitude, more or less equivalent to that of New England from southern Connecticut to central Maine. Collecting was concentrated in southern Hokkaido where the woody flora is particularly rich, this area being the meeting ground for both temperate and boreal elements. In one small area near Sapporo, the prefectural capital, 108 species of trees are native, the highest concentration in all of the North Temperate Zone. There, two broad-leaved evergreens of considerable ornamental value, Skimmia japonica and Daphniphyllum macropodum var. humile, were collected near the northern limit of their ranges.
With the help of Mr. Yojuuro Sato, a short excursion was made into central Hokkaido, where the temperature has gone as low as -40°C. Exciting collections in the lowland forest of this region included Alangium platanifolium var. trilobum and Cephalotaxus harringtonia var. nana, probably the northernmost representatives of these plants ever introduced into the United States. The primary objective in central Hokkaido was Mt. Daisetzu, a volcanic massif with still active vents and a very extensive alpine zone. At 2345 meters it is the highest point on the island. The alpine flora there is characterized by a great diversity of shrublets including species of Rhododendron, Vaccinium, Empetrum, Loiseluria, and Sieversia, a woody relative of Geum.
The second major portion of the trip was spent in the northern district of Honshu, the main Japanese island. Here we were accompanied by Dr. Kankichi Sohma, a palynologist from Tohoku University in Sendai, who is well versed in the Japanese flora, and one of his graduate students, Mr. Masamichi Takahashi. Collecting was concentrated on the higher mountains of the district, including: the volcanic Mt. Hakkoda, where Abies mariesii and Tsuga diversifolia were found at their northern-most stations, and seeds were collected from a dwarf Hamamelis japonica; the predominantly serpentine Mt. Hayachine where the most exciting finds were Betula corylifolia and Acer distylum, a maple with leaves like those of a linden; and the mountains of Nikko National Park where Trochodendron aralioides, a primitive evergreen tree, was collected near its northern limit at an elevation of 1000 meters.
In Korea, Mr. Carl Ferris Miller was our host. Several profitable days were spent in Mr. Miller’s Chollipo Arboretum on the western coast of Korea south of Seoul, and nearby, seeds of Koelreuteria paniculata, the Golden Rain Tree, were collected from one of the two localities where the species is known in Korea. A stop at an old garden on the way back to Seoul yielded one of the trip’s major surprises—a fine specimen, in fruit, of Magnolia officinalis, the Chinese Umbrella Magnolia, a species very rare in cultivation in the West.
Perhaps the most exciting excursion in Korea was to some of the higher mountains in the northeastern part of the country. Temperatures in this region fell to -30°C. during the winter of 1976-1977, so most of the plants growing there should be hardy at the Arnold Arboretum. Notable collections included Magnolia sieboldii, Paulownia coreana, Diospyros kaki, the Oriental Persimmon, and Sapium japonicum, a small tree in the Euphorbia Family with beautiful autumn coloration, and one that is not even mentioned in Alfred Rehder’s Manual of Cultivated Trees and Shrubs.
A total of 505 collections were made, representing 327 taxa in 69 families. Included were fifteen species of maple, nine of birch, five of alder (some of which are very beautiful trees), nine of viburnum, six of euonymus, and five of magnolia. With the exception of a single package, of which there fortunately was a duplicate, all of the material arrived safely at the Arnold Arboretum and is now being processed at the Dana Greenhouses. Eventually, representatives will be added to the living collections of the Arnold Arboretum, bolstering our already impressive collection of Oriental plants; others will be used for staff research projects, and the excess will be distributed to other arboreta and botanic gardens.
A future issue of Arnoldia will feature a full length article detailing more fully the itinerary, the plants collected, and the people met en route.