Scars of a landslide disaster caused by a typhoon remain on the mountain surface. A narrow river, which had been surrounded by greenery, was changed to a concrete-made waterway.

Spring water shines in the sunlight in the photo above to the left. Keiichi Tashiro is in the photo below it. Stones are placed on wasabi seedlings in ishiue cultivation in the photo at right.

Part 1: Seeking Japan's No.1

Selected wasabi (Japanese horseradish) are assembled in Tokyo's Tsukiji market from throughout the country. In its vegetable and fruit sales floor, wasabi that line the storefront of long-established intermediate wholesaler Kushiya are especially conspicuous. They are priced at more than 20,000 yen (about $170) per kilogram, which is higher than tuna sold in the adjacent seafood sales floor. This wasabi attracts customers not only in high-class sushi restaurants in central Tokyo but also overseas. If you know the flavors of maguro (tuna) and hirame (bastard halibut) served with this wasabi, you cannot eat them without it, said Masahiro Sugimoto, president of Kushiya. What wasabi elicits such high praise from the professional maven? We visited its producer, Keiichi Tashiro, 43, a farmer in Gotemba, Shizuoka Prefecture.

Exposing it to spring water

Tashiro's wasabi fields are dotted along a river that flows between the mountains. The area has an abundance of spring water, whose temperature ranges between 10 and 13 degrees throughout most of the year. His wasabi fields take in this spring water. The fields are slightly inclined so that the water spreads equally to the entire fields. However, each field differs in size and shape. He slightly changes the field depending on such factors as the amounts of sunlight and the tilt of the land. There are various cultivation methods, and Tashiro is adopting a method called ishiue (stone on). It is called that because a stone is placed on a seedling when wasabi is grown. Another method is chon-ue, whose word origin is said to be chokon to ueru (planting it slightly). In addition, there is a cultivation method of protecting a seedling from outside elements by covering it with pipes, he said. In the ishiue method, wasabi is laid on its side, so it grows horizontally. As a result, almost all the parts of wasabi are exposed to spring water and become bright green.

Even a cultivation career of 20 years

Following in the footsteps of his father, Kaoru Tashiro, 78, Keiichi began to cultivate wasabi. His career has spanned about 20 years. However, he fails even now. In 2016, wasabi grew to only about the size of the tip of a thumb in one field. He is raising a variety called Mazuma, which takes about a year and a half to one year and 10 months for the wasabi to grow from seedlings to a size large enough for shipping. The period from planting the seedling to harvesting is lengthy, unlike many other agricultural products. Because of that, it is painful when wasabi have not grown large enough to be shipped at the time of harvesting. I don't know the clear reason for the failure. If my father cultivates it, he does not experience such a failure, said Keiichi Tashiro. What his father has that he does not have is intuition resulting from experience, which is important for growing wasabi.

According to Tashiro, three factors are indispensable for wasabi cultivation: abundant spring water, avoiding strong sunlight and soil with good permeability. Seeing the degrees in the growth of wasabi, he changes the amount of water when irrigating them, mixes soil to improve its permeability and covers the plant with black plastic sheets depending on the strength of the sunlight. These works have major influences on the growth of wasabi. And even if he continues to do the same work, wasabi does not necessarily grow as idealistically as hoped.

Conquering complete destruction