Oak Forest at Katatago Hachiman Shrine

A Sacred Grove for One of Japan's Rarest Oaks

On a low wooded rise above the rice fields of Hase, in the southern reaches of Saiki City, an unbroken canopy of evergreens marks the precinct of Katatagō Hachimansha. The hill measures only about 57 meters high and roughly 1,500 meters around its base, yet the forest growing on it is one of the most botanically significant patches of woodland in western Japan. Within its four hectares grow tall straight oaks of a species so rare that this is the only forest of its kind ever designated as a National Natural Monument: Hanagagashi, the long-leafed evergreen oak Quercus hondae.

The forest received its national designation on 11 March 1978, with an additional designation entered on 14 August 1989. It is recognized under the criterion for famous trees, giant trees, and sacred shrine groves. While prefectural Hanagagashi stands exist at other shrines, this is the only example accorded full national protection.

What Is Hanagagashi, and Why Does It Matter?

The name Hanagagashi divides not as hana-ga-gashi but as ha-naga-gashi: the long-leafed oak. Among Japan's evergreen oaks, none carries leaves so narrow and elongated. They reach 7 to 15 centimeters in length but only 1.5 to 3 centimeters in width, tapering to a fine point, with sharp teeth along the upper half of the blade. The trunk runs almost straight upward, and mature trees can stand 20 to 30 meters tall.

The species belongs to the red-oak subgenus Cyclobalanopsis, a group whose acorns sit in caps marked with the characteristic concentric rings of Japan's kashi oaks. Its natural range is restricted to scattered low-elevation pockets in Kyushu and Shikoku: Miyazaki, Kagoshima, Oita, Kochi, and Ehime. It is believed to have once grown in Kumamoto as well, but no wild population survives there.

Japan's Ministry of the Environment lists Hanagagashi as Vulnerable on the national Red List. Regional assessments place it higher still: Critically Endangered in Ehime and Kochi, Endangered in Oita. Genetic studies have shown that the Shikoku and Kyushu populations have diverged from one another and that overall genetic diversity is roughly two-thirds that of the related Arakashi oak, raising concerns about inbreeding as remaining stands grow isolated. In Oita, individual trees outside protected sites have at times been cleared by foresters who considered them an obstacle to harvesting neighboring cedar plantations.

That history is what makes the Katatagō Hachimansha grove unusual. The forest has reportedly never been clear-cut. Hanagagashi grows densely here alongside the chinquapins Castanopsis cuspidata (Kojii) and Castanopsis sieboldii (Sudajii). The largest specimens reach trunks of roughly 2.7 meters in girth for Hanagagashi, with some individuals approaching 25 meters tall and nearly a meter in diameter. Kojii and Sudajii grow to comparable size.

The Shrine That Saved the Forest

Katatagō Hachimansha is also known locally as Jō Hachimangū, after the small fortress (jō) that once stood on the hilltop. Tradition places its founding on the fifteenth day of the eighth month of Kōnin 7 (816 CE), during the early Heian period. The shrine enshrines Hondawake no Mikoto along with Tarashinakatsuhiko no Mikoto and Okinagatarashi-hime no Mikoto, the standard Hachiman triad.

The shrine originally stood at the summit of the hill but was moved to its present location in Kyōhō 6 (1721), when it was elevated to the principal shrine of Katatagō district. A weathered stone hokora at the old summit site still bears inscriptions to the inner sanctum of the Hachiman cult, to Ōyamatsumi no Kami, and to a local clan deity associated with the Saeki family. The current main hall was constructed in Tenpō 2 (1831) by Nonoshita Ryūbei, a master shrine carpenter from Komae, and is regarded as one of the finest examples of shrine architecture in the Saiki region.

Because the hill served simultaneously as a place of worship and as the visual marker of the village, its forest was treated as sacred ground. Surrounding woodlands were cleared and replanted with cedar for timber many times over the centuries, but the hill itself was let alone. The result, twelve centuries on, is a patch of old-growth lowland evergreen forest of the kind that once stretched across much of southwestern Japan but is now almost entirely gone.

What You See on the Climb

The approach is by way of a long, straight stone stairway that rises from the western foot of the hill and runs upward through the forest itself. The steps face southwest, so afternoon light cuts at a low angle through the canopy and catches the silvery-gray bark of the older oaks. Hanagagashi concentrates on the western slope and at the top of the rise, while Kojii and Sudajii dominate the eastern side.

The sub-canopy and shrub layer carry their own catalog of species rarely found together at low elevation: Kobanmochi (Elaeocarpus japonicus), Yamabiwa, Taiminachibana, Misaonoki, Satsumaruriminoki, and Kuroki. Below them grow ferns and orchids that signal undisturbed soil: Ookaguma, Benishida, Tsurukōji, Kohashigoshida, Kijinooshida, Koyaburan, Shishigashira, and Muyōran, a leafless mycoheterotrophic orchid that depends on fungal partners and cannot tolerate disturbance. The presence of Muyōran and the rare Nagiran orchid is taken by botanists as a marker of soil and root systems that have remained intact for centuries.

Within the surrounding prefecturally designated Jō Hachimansha no Shizenrin, which covers the wider grove, surveys have recorded 229 plant species. Visitors will not necessarily identify them, but the impression of layered, complex woodland, dim at midday and humid even in late autumn, is unmistakable.

Festivals and the Living Tradition

The shrine's annual festival falls on the Sunday closest to April 3, when villagers carry the deity in procession and perform Saeki Kagura, a sacred dance tradition designated as an Intangible Folk Cultural Property of Oita Prefecture. The kagura is performed in spring, summer, and autumn at this and other shrines in the Katata and Aoyama districts. The Shimojō walking-stick dance, another local performance form, is also associated with the area.

These festivals are open to anyone who happens to be in the village on the day, though they remain modest community affairs rather than tourist events. Watching the procession move up the long stone stairway under the oaks gives a tangible sense of why the forest has been left untouched: it is not preserved as a museum specimen but kept as the home of a god.

The Surrounding Area

Saiki City occupies the southeastern corner of Oita Prefecture and is the largest municipality in Kyushu by area, taking in coastline, river valleys, and the rugged interior of the Sobo-Katamuki mountain range. The Hase area sits inland, reached by following the Banjō River upstream from the coast.

Within easy driving distance lie Saiki Castle ruins on Shiroyama overlooking the city, the historic samurai quarter at Yōkamachi, the fishing harbor at Yonōzu, and the Banjō and Komou river valleys. The coast east of Saiki forms part of the Nippō Kaigan Quasi-National Park, with the cliffs and pine-clad islands of the Bungo Channel. For a botanically curious traveler, Saiki's other Hanagagashi grove at Yasaka Jinja in the former Yayoi township is also accessible, though the prefectural designation there does not allow entry into the stand itself.