Origins of the Koshu Grape
It was the ancient name for the area - Koshu - that gave the native Koshu grape its name. It is thought that up until the Edo period (1603-1868), it was the only grape variety cultivated in Japan.
Koshu grapes have evolved over the centuries to suit the Japanese environment, their thick skins making them comparatively resistant to disease in this humid climate. They are a distinctive dusky pink colour with long clusters of medium-sized round fruit.
Although native to Japan, the Koshu grape belongs to the European grapevine species Vitis vinifera. It falls under the oldest of the three cultivars of this species, Proles orientalis, making it a relative of grapes heralding from the Caucuses, known as the birthplace of viticulture. Analysis shows that it also contains some DNA from wild Chinese grapes, which helps to explain its resilience.
From Vision to Reality
Exactly how and when the Koshu grape made its way to Japan is still shrouded in mystery but one thing is clear: grape cultivation originated in Katsunuma, the present-day centre of Koshu Valley wine production.
Two common theories exist. The first dates to the year 718 during the Nara Period (710-784 CE) and holds that grape vines were first introduced by Buddhist monk Gyoki in the grounds of Daizenji Temple in Katsunuma. Gyoki is said to have founded the temple after visiting the area from Nara and seeing a vision of the Buddha of Healing and Medicine holding a bunch of grapes. Grapes were therefore initially grown for medicinal purposes.
The second theory contests that grape cultivation began some 400 hundred years later during the Kamakura Period (1185-1333 CE) when, in 1186, local farmer Kageyu Amemiya discovered an unfamiliar vine growing by the roadside in Katsunuma and transplanted it to his own land.
These two stories are not mutually exclusive, however. It is thought that grapes made their way to Japan from China after travelling from Europe on the Silk Road, a theory supported by the grape’s DNA. The Nara Period, when Gyoki is said to have started growing grapes at Daizenji Temple, was a time of great Chinese influence on Japan, with Japanese monks travelling to China to study Buddhism and bringing back with them knowledge of, and ingredients for, traditional Chinese medicine. It is therefore likely that both stories have some truth in them - seeds or vines from China were planted in temple fields and rediscovered by chance many years later. Indeed, in its heyday, Daizenji Temple housed 3,000 monks and its grounds covered a large swathe of Katsunuma, likely including the path back from a local fire festival where it is said Kageyu Amemiya found the vine in 1186.
Koshu grapes are traditionally grown with the overhead pergola trellising method, known locally as tanashiki. Some growers are experimenting with growing Koshu on the VSP (vertical shoot positioning) trellising system but this is mostly reserved for international grape varieties.
Grape trellis was originally made with bamboo supported by wooden posts, an approach said to be introduced by the doctor Tokuhon Nagata in the early Edo Period. In the early Meiji Period - 1880's - the overhead supports were replaced by metal poles and in 1898 the current wire lattice design was invented by a local postmaster inspired by telegraph wires. The majority of the support posts are now made from more durable concrete, although a few wooden posts remain in use.