Ura-Izu-Oshima Part 1

Izu Oshima, with an area of 90 sq. km, is the largest of the Izu island group (shoto). It is located about halfway between Cape Su-no-saki on the southern tip of the Boso Peninsula and Shimoda on the southeast tip of the Izu Peninsula. Mount Mihara (764 meters), an active volcano, dominates the whole island.

The climate of Izu Oshima is moist temperate maritime, with mild winters and cool summers. Annual rainfall is 2,800 mm; the wettest times of the year are during the tsuyu in June and July and in September and October, when typhoons are likely.

In winter strong winds cross from China, moving in a north-easterly direction, enter Honshu through Wakasa Bay in Fukui and exit down through Ise Bay, in Aichi. The winds then turn northwards towards the Izu Islands.

Meanwhile, cold, slow-moving winds descend from the Chubu mountains, the rocky backbone of Honshu, to cross Tokyo Bay and the Boso Peninsula. Both of these winds converge at the Izu Shoto. The coldest month is February, and the lowest temperature ever recorded was minus 4 C, which was Feb. 3, 1996. Frost may fall anytime from December through February — but mostly in February.

It was mid-February when I took my bicycle on the ferry from Atami, Shizuoka to Okada, the Oshima ferry port, to see the 200-year-old camellia tunnel, the 800-year-old cherry tree and the Japanese chinquapin forest.

The island is part of Fuji-Hakone-Izu National Park, and comes under the prefectural jurisdiction of Tokyo. It has a population of some 10,000, and the main town is Motomachi on the western side (omote). On the southern tip is Habu, a fishing port; Okada is on the northern end of the island. I stayed in the Central Lodge, which has a very beautiful location below rugged Kushi ga Mine (“Comb Top”) mountain, halfway between Okada and Habu on the eastern side of the island (ura).

Ura-Oshima is a refuge from the hustle and bustle of the large cities. I met a man who said he comes to Ura-Oshima 20 or 25 times per year by overnight ferry from Tokyo to fish off the rocks, cooking and eating what he catches. He loves solitude and only visits the island during the off season, from November until April. He has never been to Motomachi, he says. There are too many people there.

Just a short way beyond Okada pier on the Ura-Oshima side there is a spectacular sight: a tunnel of camellias almost 400 meters long! These camellias are treelike and tall enough for large tour buses to pass beneath. The oldest are over 200 years old. The old road from the town offers another camellia tunnel; very few cars use it, so it’s ideal for cyclists.

Beyond the camellia tunnels the road climbs gently towards the camellia garden (of which more in my next column). Then from the garden the road climbs through the magnificent woodland of tall evergreen Japanese chinquapin (sudajii, Castanopsis cuspidata var. sieboldii).

The forest on the island is classified as shoyo-jurin, a term that applies to evergreen woodlands in warmer areas. In June 1951 these Japanese chinquapin woodlands, which stretch over much of the northeast slopes of Mount Mihara, were designated a natural monument.

The woodland Castanopsis belong to the beech family (buna-ka, Fagaceae), with an estimated 110 species found in the tropics and warm temperate areas. Chinquapin (an Algonkian Indian word) can grow as tall as 30 meters and, back from the road, some have trunks 6 meters thick.

The leaves are leathery, toothed, arranged alternately (gosei) on the branch, around 6-15 cm long and 2-3 cm wide, the topside dark green; the brownish underside has many tiny hairs. In May or June, drooping, golden pistillate female flowers, 5-10 cm long, appear. The male flowers, also gold-colored but pointing upwards, bloom on new twigs 8-12 cm long. The blossoming chinquapin makes very attractive scenery.

Apart from its beauty, the chinquapin is a valuable tree. Its nuts are sweetly edible. It is often planted in windbrakes and firebreaks. Chinquapin timber is used for everything from shipbuilding and housing construction to cabinetmaking and turnery — even rice bowls are made from it. If there are no more eruptions from Mount Mihara the chinquapin trees should continue to spread and remain the dominant tree in these forests.

Farther on up there is a junction in the road, and just a short distance beyond the junction, on the lefthand side of the road, is the celebrated Oshima cherry (Prunus lannesiana var. speciosa), designated a special natural monument by the Japanese government. This tree is estimated to be over 800 years old, and each spring, fresh new flowers bloom. A hybrid between the Oshima cherry and Edo higan (P. pendula, forma ascendens) was made sometime during the Edo Period (1603-1868). The result was the Yoshino cherry (P. pendula yedoensis), the most popular flowering cherry in Japan.

Around this ancient cherry grow 5- or 6-meter-tall specimens of kakure-mino (Dendropanax trifidus), an evergreen of the ginseng family (ukogi-ka, Araliaceae) often planted by gardeners because of its ability to withstand shade. Its dark green leaves have two or three lobes. Genus Dendropanax has an estimated 60 species, mostly in the tropics of Asia and South America; D. trifidus is the only species that is native to Japan, and does not grow naturally north of Sendai.

Farther up the slope are masses of aridoshi (Damnacanthus indicus), a low-growing evergreen shrub with spines 1-2 cm long. Its tubular white flowers (each about 1 cm) are borne singly or in pairs at the tips of branches in May; shiny red berries ripen in winter.

The distance from the Oshima cherry to Mount Mihara is around 7 km, all uphill. This road has been named the Ajisai Rainbow Line. Ajisai is the Japanese name for hydrangea; two kinds, tama ajisai (Hydrangea involucrata) and lace cap hydrangea, gaku ajisai (H. macrophylla forma normalis) grow naturally on the island. The best time to see hydrangea is June until mid-July.

Close to the summit is Mihara Hot Spring, where visitors can relax in the open-air bath (roten-buro) with a nice view of the volcano for 800 yen.

The most recent eruption of Mount Mihara was Nov. 16, 1986; the entire population had to be evacuated to the mainland. Previous eruptions this century were in 1950-51 and in 1912-15. The volcanic ash area to the east of the summit is so large that locally it’s known as the Great Desert (Dai Sabaku). Alder trees (oba-yashabushi, Alnus sieboldiana) are quickly colonizing the perimeter of this desert, though.

The Izu Oshima Vulcanology Museum near Motomachi offers information on active volcanoes all around the world.

Really, though, you need to stay two nights to enjoy this beautiful island.