Boroishiyama

A Warm-Temperate Forest on the Edge of Miyazaki City

The Boroishiyama (双石山, Boroishiyama) is a 509-metre mountain in Kagamizu, Miyazaki City, Miyazaki Prefecture, whose natural forest was designated a Natural Monument in 1969.

The Agency for Cultural Affairs describes part of a national forest in southern Miyazaki, protected as a scientific reference forest. It is a warm-temperate broadleaf forest of evergreen oak, chinquapin and tabu, one of few such examples left in Kyushu.

Miyazaki City calls it the natural forest closest to the coast, on a steep mountain with folding-screen cliffs on both sides of the ridge. The characters 双石 are read boroishi.

Nature on the Mountain

Miyazaki City explains that the mountain is made of tilted, uplifted Miocene sandstone and conglomerate, with a winding gorge between it and the Kanbachiyama and Tokusoyama ridges to the east.

The forest is a typical warm-temperate stand of chinquapin and evergreen oak, rare as natural woodland. The city counts 579 species of higher plants in 115 families, including plants at the northern and southern limits of their ranges, and 157 species of mosses.

For animals, the Agency names the Japanese dormouse and the common jay butterfly among the valuable species. Miyazaki City records some 660 species of insects in about 115 families, including southern and local species, and about 50 species of birds, and notes that much remains unsurveyed.

What to Look For: Strange Rocks along the Trail

The trekking route introduced by Miyazaki City climbs from the Kotani trailhead past Iwaya Shrine, Tengu Rock, the Elephant Graveyard and the second viewpoint to the summit, then descends to the Kudaira trailhead. Tengu Rock is a huge odd-shaped rock, the Elephant Graveyard a space hemmed in by towering rock, and the second viewpoint looks over the Miyazaki Plain to the Hyuga Sea.

Cliffs of sandstone and conglomerate under a cover of evergreen forest give the Boroishiyama its character. Miyazaki City also presents it as the best place for nature watching close to the city.

Visiting the Boroishiyama

The Boroishiyama is explored on foot by its trails. On Miyazaki City's route, the climb from the Kotani trailhead to the summit takes a little over three hours, and the descent to Kudaira about one hour. There are rocky and steep sections, so go equipped for hiking.

As a Natural Monument, plants and insects must not be collected. For the trails, contact the Miyazaki natural recreation forest council (secretariat: Miyazaki City forestry section, 0985-21-1919); for the cultural property, the Miyazaki City cultural properties section, 0985-85-1178.