A small-seeded kaya in the hills of Obara
In Obara, a hamlet in the western part of Shiraishi City, a single conifer rises close to thirty meters, well above the rooftops of the houses around it. Its trunk measures about 2.6 meters around at chest height and roughly 3.2 meters at the base. Local estimates place its age at around three centuries.
The tree is a kaya, the Japanese nutmeg-yew (Torreya nucifera). What sets it apart is that it belongs to an uncommon variety known as kotsubugaya, literally the "small-seeded kaya." It has been protected as a National Natural Monument since February 1943, and it is one of only two trees in the country to hold that status as an example of the variety.
The kaya, and the variety that puzzled botanists
Kaya is an evergreen conifer of the yew family, found only in Japan. It grows in temperate forest from roughly the latitude of Yamagata and Miyagi prefectures southward, and it grows slowly, so a large specimen represents many human lifetimes. Its hard, fine-grained timber has long been the preferred material for the boards used in the games of go and shogi, and its seeds were once roasted as a snack and pressed for lamp oil.
An ordinary kaya produces an elongated seed wrapped in a green fleshy coat. In the late 1920s, a botanist examining kaya trees in Mie Prefecture found one whose seeds were almost round and only about half the usual length, roughly 18 to 20 millimeters across including the outer coat. He described it in 1928 as a distinct variety and gave it the name kotsubugaya. The needles of this variety differ as well: instead of the sharp, prickly tips of a common kaya, they end bluntly or with only a faint point, and the branchlets grow unusually thick and close together.
The Obara tree was identified as the second example of the variety known anywhere in Japan.
Why it became a National Natural Monument
The tree was designated on 19 February 1943, under the criterion that protects notable, old, and giant trees. Two things made it worth protecting.
The first is simple scale. A kotsubugaya of this height, with a healthy crown and vigorous growth, is rare. The variety itself is scarce, and a giant example of it scarcer still.
The second reason is geographic. Obara lies in southern Miyagi, close to the northern edge of the kaya's natural range. The original kotsubugaya had been found far to the southwest, in Mie. A small-seeded variety appearing in two places several hundred kilometers apart raised real questions about how it had spread, and that distribution puzzle is part of what the designation was meant to preserve.
The first Mie tree was lost in a storm in 1959 and removed from the register. A third kotsubugaya was identified in Mie in the early 1990s. The Obara tree is therefore the oldest surviving designation of its kind.
What to look for
Standing at the base and looking up gives the clearest sense of the tree's age and reach. The crown climbs through several stories of open air before it thins against the sky.
Up close, the foliage rewards attention. Reach into a branch of an ordinary kaya and the needle tips will prick the skin; here they do not. The soft-tipped needles and the dense packing of the branchlets are the features that first told botanists this was something other than a common kaya. In autumn, the small rounded seeds that gave the variety its name can sometimes be seen among the foliage or on the ground beneath it.
It is worth remembering that this is a working tree in an inhabited place, not a garden specimen. It has grown here, beside the houses of Obara, far longer than the present village has looked the way it does today.
Visiting Obara
The tree stands within the Obara settlement and is best appreciated from the public road nearby. There is no admission charge, no gate, and no dedicated visitor facility. This is a quiet rural neighbourhood, so it helps to keep voices low and to stay out of private gardens.
Obara sits in the upper valley of the Shiroishi River, in the southwest corner of Shiraishi City near the boundary with Shichikashuku. The practical base for the area is the cluster of sights around Zaimokuiwa Park, a short drive away, where there is parking, a rest area, and seasonal refreshment. Reaching Obara is easiest by car; from Shiroishi-Zao Station on the Tohoku Shinkansen the drive takes around thirty minutes.
Around Obara
Obara fits a surprising number of sights into a small area.
Zaimokuiwa, also a National Natural Monument, is a cliff of columnar rock rising about a hundred meters above the river. The hexagonal and pentagonal columns stand so evenly that they resemble stacked timber, which is what the name means. A local legend tells of a master carpenter who, unable to finish a hall before dawn, flung his lumber into the river, where it turned to stone.
Obara Onsen, a hot-spring hamlet in the gorge below, has welcomed bathers for centuries. The Meiji-era writer Tokutomi Soho was taken enough with the ravine to name it Hekigyokukei, the "jasper gorge." The valley shows best in fresh spring green and in autumn colour.
Obara has a second protected kaya as well. The Hidarimakigaya, designated a National Natural Monument the year before the kotsubugaya, is another variety, one whose seeds carry distinctive spiralling ridges. Few places anywhere can claim two nationally designated kaya varieties.
Further afield, the much-photographed Zao Fox Village lies in the same part of Shiraishi, and Shiroishi Castle, a faithfully reconstructed keep, stands in the city centre.
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Q&A
- How is a kotsubugaya different from an ordinary kaya?
- Its seeds are roughly half the usual length and almost round, about 18 to 20 millimeters across including the outer coat. Its needles end bluntly rather than in a sharp point, and its branchlets grow notably dense. Otherwise it is the same species, the Japanese nutmeg-yew.
- How old is the tree?
- There is no precise figure, but local estimates place it at around three hundred years. Its measured girth and height are consistent with a tree of considerable age.
- Where is it, and how do I get there?
- It stands in the Obara district of Shiraishi City, in southern Miyagi. The simplest approach is by car, about thirty minutes from Shiroishi-Zao Station; the area around Zaimokuiwa Park makes a convenient base.
- Is there an entrance fee or visitor facilities?
- No. The tree can be viewed from the public road at no cost. There is no gate or staffed facility, so visitors are asked to respect the surrounding homes and gardens.
- When is the best time to visit?
- The tree is evergreen and rewarding year-round. Pairing a visit with the Obara gorge is most pleasant in late spring or in autumn, when the valley's foliage is at its peak.
Basic Information
| Name | Obara no Kotsubugaya (小原のコツブガヤ) |
|---|---|
| Location | Obara, Shiraishi City, Miyagi Prefecture |
| Designation | National Natural Monument |
| Date of designation | 19 February 1943 |
| Species | Kaya, the Japanese nutmeg-yew (Torreya nucifera), kotsubugaya variety |
| Approximate height | About 30 m |
| Trunk girth | About 2.6 m at chest height; about 3.2 m at the base |
| Estimated age | About 300 years |
| Access | About 30 minutes by car from Shiroishi-Zao Station (Tohoku Shinkansen) |
References
- Database of National Cultural Properties (Agency for Cultural Affairs): Obara no Kotsubugaya
- https://kunishitei.bunka.go.jp/bsys/maindetails/401/198
- Shiroishi City: Designated Cultural Property, Obara no Kotsubugaya
- https://www.city.shiroishi.miyagi.jp/soshiki/30/376.html
- Cultural Heritage Online: Kuzoji no Kotsubugaya
- https://bunka.nii.ac.jp/heritages/detail/201936
- Toba City: National Cultural Property, Kuzoji no Kotsubugaya
- https://www.city.toba.mie.jp/soshiki/k_shakaikyoiku/gyomu/rekishi_bunkazai/bunkazai/2/2213.html
Last verified: 2026.05.22