Ohatsuki Ginkgo Tree in Yagisawa

A ginkgo that bears pollen on its leaves

The leaves of this ginkgo do something ordinary ginkgo leaves never do. Along the edge of the fan-shaped blade, small pollen sacs occasionally form directly on the leaf itself, instead of hanging from the separate catkin-like stalks where a ginkgo normally carries them. A ginkgo that produces reproductive parts on its leaves in this way is called an ohatsuki ginkgo, from a Japanese word meaning roughly "attached to the leaf." The tree standing in the Kami-Yagisawa district of Minobu is one of the most closely studied examples in Japan.

It was designated a National Natural Monument on July 12, 1940. The tree grows in the precinct of a small shrine, known locally as Miyanomae Shrine and also recorded as Yama Shrine, set among houses a short walk east of the Fuji River. There is no resident priest. The trunk measures about 2.8 meters in circumference at eye level, with a more recent local measurement putting it closer to 3 meters, and the crown reaches roughly 25 meters. For a celebrated old tree these are modest figures. Its importance lies elsewhere.

Japan's only designated male ohatsuki ginkgo

Ginkgo trees are dioecious: an individual tree is either male or female, and only female trees bear the soft, strong-smelling seeds known as ginkgo nuts. In most ohatsuki ginkgo the structures that form on the leaves are these seeds, so nearly every well-known ohatsuki ginkgo is female. The Yagisawa tree is male. What appears on its leaves is not seeds but anthers, the organs that produce pollen.

Seven ohatsuki ginkgo are designated as National Natural Monuments across Japan, and this is the only male one among them. Counting male ohatsuki ginkgo regardless of designation status, just two are confirmed in the entire country, and both grow in Yamanashi Prefecture. The other is at Yakuoji temple in Ichikawamisato, which carries a prefectural designation.

The scientific record began on the far side of the river. In July 1891 the botanist Shirai Mitsutaro examined an ohatsuki ginkgo at Jotakuji temple, in what was then Shimoyama village, and reported the leaf-bearing phenomenon to the academic world. The following spring, in April 1892, Fujii Kenjiro surveyed the area and identified two more trees: the female one at Hongokuji temple and the male one at Yagisawa. In 1896 Fujii published his finding that ohatsuki ginkgo, like ordinary ginkgo, are divided into male and female. His paper and illustrations were cited widely, in Japan and abroad.

When the tree was placed under national protection in 1940, it fell under the criterion covering notable, ancient, and anomalous trees. Its value rests partly on being a botanical specimen of an unusual leaf form, and partly on its role as a fixed reference point for research, a single identifiable tree that scientists have returned to for well over a century. There is a quieter ecological dimension as well. A 1931 record of Yamanashi's notable trees already noted that pollen from this male tree, carried on the wind across the Fuji River, reaches the cluster of female ohatsuki ginkgo on the opposite bank. Botanists still consider the Yagisawa tree closely tied to the seed-bearing of the female ohatsuki ginkgo at Jotakuji, Hongokuji, and Jofukuji in the Shimoyama area.

The branch that changed sex

In early October 2011 something happened that no record had ever described for this tree. Local residents noticed ginkgo nuts on a male tree. About forty of them, clustered like a bunch of grapes, hung from a branch eight to ten meters up. A male ginkgo bearing seeds is itself rare; seeds arranged in a grape-like cluster had, by one local researcher's account, never been reported anywhere. According to village tradition the tree had been planted roughly 180 years earlier, and in all that time it had never fruited.

Because the tree is a National Natural Monument, examining it required permission from the Agency for Cultural Affairs, and the nuts hung too high for easy study. A team led by the botanist Osada Toshiyuki applied in 2015 and, once approved, climbed into the crown. They found the change confined to a single branch about eight meters up. Only that branch carried seeds. Analysis of a sample taken from it pointed to a somatic mutation, a genetic change arising in the ordinary cells of one branch, which had produced a partial sex change from male to female.

The seeds from the altered branch were sown at the Botanical Gardens of the University of Tokyo, and cuttings and grafts of the branch were propagated for further study. Reports of sex change in ginkgo exist elsewhere, including a famous old male tree at Kew Gardens in England, but those cases are clouded by uncertainty, such as the earlier grafting of female branches. The Yagisawa tree, observed and protected as a national monument for decades, gives researchers an unusually clean case. Work on what it can reveal about how sex is determined and expressed in plants continues.

Seeing the tree and the wider Minobu area

The tree rewards a slow look. The leaf anomaly is small and seasonal, and most of the foliage is perfectly ordinary, so finding a leaf with an anther or a seed on its blade takes patience. Autumn is when the tree is at its best, the fan-shaped leaves turning a clear gold from the middle to the end of November. The shrine precinct is quiet, and the ginkgo stands within the everyday life of the village rather than apart from it.

The three Minobu ohatsuki ginkgo make a natural route for anyone drawn to the variety. The female trees at Jotakuji and Hongokuji lie across the Fuji River in the Shimoyama area. The Jotakuji tree, once a giant of around 23 meters, was toppled by a typhoon in 2018; left lying in the temple grounds, it began to send out new shoots the following year. Minobu is also the gateway town to Kuonji, the head temple of Nichiren Buddhism on Mount Minobu, reached by a ropeway up the mountainside, and the surrounding region is known for views of Mount Fuji from Lake Motosu. JR Hadakajima Station on the Minobu Line lies about a fifteen-minute walk from the tree.