In the western part of Hyogo Prefecture, nestled among broadleaf deciduous forests at the foot of Mount Hyo-no-sen (1,510 meters), lies Oberland Garden (also known as Tajima Kogen Botanical Garden). First opened to the public in June 1997, Oberland has a total area of 17 hectares, and boasts over 1,300 species and cultivars of plants.
The garden is located at an altitude of 700 meters on the Japan Sea side of the Chugoku mountain range, and receives around 3 meters snowfall each winter; the Hakone wetland botanic gardens, which I have discussed in this column before, are 650 meters above sea level. The main difference between the two is that while Hakone is primarily a wetland garden, Oberland is a woodland garden, although it does contain a natural moor (shitsugen) at its center which contains many interesting plants.
May and June are the best time of the year to see the mass of spring flowers at Oberland; I visited the garden on a cool sunny morning in May.
The main entrance building is a log house. Inside is a steak restaurant known as Hutte Brunnen, which serves the famous local Tajima beef. Right at the entrance gate there is a young European purple beech (seiyo-buna pa-purea, Fagus sulvatica forma purpurea), which in time should make a very attractive specimen tree.
Once inside the entrance the pathway leads down into the woodland garden. I was thrilled to see the yellow flowered kirengeshoma (Kirengeshoma palmata), my favorite Japanese perennial, which has golden yellow flowers that bloom in early August on stems up to 1.2 meters tall. Along either side of the pathway are many different types of shade woodland perennials. Hostas (giboshi, Hosta sieboldiana and other species) are planted in great numbers throughout the garden.
The woodland is mainly composed of secondary forest (nijirin) and belongs to the temperate climate zone (ontai rakuyo-jurin). The tree growing naturally in greatest numbers in the garden is the Japanese horse chestnut (tochi-no-ki, Aesculus turbinata).
In this garden it is easy to get up close to examine the huge palmate leaves because there are so many young trees. The Japanese oak (mizu-nara, Quercus mongolica var. grosseserrata) and the true Japanese chestnut (kuri, Castanea crenata; no relation to the Japanese oak) can also be seen, along with the white flowers of the willow-leafed magnolia (tamushiba, Magnolia salicifolia) in early spring. A lovely scented terrestrial orchid known as shunran in Japanese (Cymbidium goeringii) was in flower during my visit. It was nice to see much that much local flora is being preserved in the garden.
Viburnum dilatatum, a woodland deciduous shrub that bears pretty white flowers in cymes and in November small but attractive red berries, was also in bloom. Climbing hydrangea (tsuru–ajisai, Hydrangea paniculata) was growing naturally on the trunks of some trees. All of these and lots more could be seen on the yamabe-no-michi (mountain walk). The European lily-of-the-valley (doitsu-suzuran, Convallaria majus) has been planted in various parts of the garden. I always enjoy the fragrance from these lovely woodland perennials.
The light blue-purple colored flowers of the Japanese woodland iris (shaga, Iris japonica) were also in full bloom. This evergreen iris is interesting, not only because it requires woodland shade to grow successfully but also because it has triple the number of chromosomes (senshokutai) of normal flowering plants. As a result this triploid (sanbaitai) iris cannot set seed; it uses an asexual (musei) vegetative reproductive mechanism to survive.
In the center of the garden there is a large lawn area, with big trees carefully preserved so as to give shade during the summer. At the edge of the lawn and woodland lots, white foam flower (Tiarella wherryi) stalks could be seen. T. wherryi is native to the Appalachian Mountains in the eastern U.S. The native Japanese variety is T. polyphylla (zuda-yakushu) which grows in coniferous woods (shinyo-jurin) in the Kinki district and further northward.
The most impressive tree in the garden is a magnificent old specimen katsura tree (Cercidiphyllum japonicum), locally known as Wachi dai katsura. Reckoned to be 1,000 years old, the tree has a girth of 16 meters and straddles a cool mountain stream, which has formed a tunnel through the center of the trunk. The temperature of the stream apparently remains at 5 C all year round.
There are two more ancient katsura trees nearby Oberland Garden, one in Uwano-kogen, and the other on Betsu-momiya below Mount Hachibuseyama. All three are protected by the Hyogo prefectural government.
Close to the wachi dai katsura I saw an interesting shrub, with tiny green flowers carried at the center of its leaves! The name of this deciduous shrub is hana-ikada (Helwinga japonica) and it belongs to the dogwood family (mizuki-ka, Cornaceae). Although the flowers are not showy, the very unusual way in which they are displayed is fascinating. In August the shrub bears shiny black fruit 7 mm in diameter, and its leaves are edible.
Close to Torokawa Moor in the center of the garden the true skunk cabbage (zazen-so, Symplocarpus renifolius) grows naturally. This same species also grows in other parts of East Asia and in the northeast of North America. A member of the aroid family (tennasho-ka, Araceae), this fetid perennial flowers before its large leaves emerge. The blooms are surrounded by a large showy spathe (butsuen-ho) 10-20 cm tall. Inside the spathe, yellow flowers are produced 2-3 cm in diameter.
Also natural to the moist soil near the moor is the leopard plant (o-takara-ko, Ligularia fischerii), which bears yellow flowers 4 cm in diameter on long flowering stems which grow between 1-2 meters tall, flowering from July to October. Purple loosestrife (Ezo-mizuhagi, Lythrum salicaria), which can be found all across the Northern Hemisphere including the British Isles, bears purple flowers on stems 50-150 cm tall in July and August.
Oberland Garden is still very young, and I do hope that the maintenance will always be kept to a high standard, as along the Japan Sea side of the country this style of garden is still rare. The one drawback is that while a lot of the plants have labels, many of the hostas and other plants have none; a pity because there are so many fine hostas in the collection.