Shaping the Future of Japanese Wine: Secondary Induced Shoot Cultivation Delivers Delicious Grapes in an Era of Climate Change

Rising temperatures caused by a changing climate have impacted agriculture in multiple ways, and the cultivation of wine grapes is no exception. Suntory’s Tominooka Winery has implemented a variety of measures in response to the marked rise in summer temperatures over the past several years. Tatsuki Shiga, from the Wine Production Department of Suntory Spirits Limited, profiles secondary induced shoot cultivation, a method in use at Tominooka Winery in Yamanashi Prefecture, that is attracting attention from many grape growers.

Bringing the Tominooka Uniqueness to Wine

After researching wine at the University of Yamanashi, I wanted to get involved in winemaking and got a job at a Yamanashi wine maker. Then, I went on to join Suntory’s Tominooka Winery which had begun using secondary induced shoot cultivation, a method designed to address a major challenge facing today’s wine industry. There, I was impressed by the “Yatte Minahare” culture, which encourages people to take on challenges without fear of failure.

Secondary Induced Shoot Cultivation

By trimming the first shoots on the grape vine and allowing secondary shoots to subsequently develop, the start of grape maturation can be delayed from late July to early September, and harvesting can be shifted to mid- to late November. This cultivation approach meets the challenge posed by the rising temperatures due to climate change. Maturing the grapes when temperatures are lower facilitates production of high-quality grapes. Suntory began using this method in 2021 as part of joint research with the University of Yamanashi, which holds the patent.

There is no correct approach to winemaking. As such the path is endless, and you can constantly pursue ways to make your wine better. In countries like France and Italy, each region has its grape varieties and cultivation methods that are regulated by law, and applying new approaches like secondary induced shoot cultivation in response to climate change is not easy. But at Tominooka Winery, we have the freedom to approach winemaking flexibly. As times and the climate change, we hope to continue our pursuit of grape varieties and methods of cultivation and winemaking suited to our local terroir, and continue to produce high-quality wines that convey the Tominooka uniqueness.

The view from the winery observation deck takes in Mounts Fuji and Kaikomagatake and the Yatsugatake peaks, with golden autumn vineyards stretched out below.

Secondary Induced Shoot Cultivation Contributes to Wine Quality in a Tangible Manner

Compared to well-known wine-producing areas around the world, Japan’s climate and environment can’t be regarded as especially favorable. I sometimes wonder, “Aren’t we making wines in one of the most difficult places in the world?” High-quality grape cultivation requires a significant drop in nighttime temperatures, but year by year, Japan’s summer nighttime lows have been rising, with Tominooka Winery experiencing the warming trend to a significant extent starting roughly a decade ago. In response, we began to focus on cultivating Petit Verdot grapes, which are comparatively heat-resistant, while introducing secondary induced shoot cultivation with our Merlot grapes starting in 2021. The results were eye-opening. First of all, grapes produced with this technique were significantly better-tasting as fruit. In addition, the quality of wine made from these grapes was quite a bit better. In 2022, we expanded the growing area dedicated to this approach by a factor of eight, and began using secondary induced shoot cultivation with other varieties such as Chardonnay and Cabernet Sauvignon.

Grapes grown with secondary induced shoot cultivation are small, with thicker skin. They have concentrated sweetness and acidity, rich bouquet, and robust flavor.

In secondary induced shoot cultivation, we wait until the primary shoots produce blossoms and fruit clusters, then trim off each shoot. This means we must mobilize a large labor force for a short, specific period, which is something that conventional cultivation does not require. To realize this, we recruit employee volunteers to support this task, and last year we received help from over 100 employees who came from all over Japan. In addition, since the timing differs from that of conventional cultivation, there are disease and pest risks that are specific to secondary induced shoot cultivation. At the same time, we want to minimize the use of pesticides, and each year we strive to discover the most effective chemicals and spraying times. Furthermore, we must finalize our cultivation plans in February or March, but it is difficult to predict summer and autumn temperatures at that point. Temperatures are not always as anticipated, which poses a challenge to achieving a consistent approach. In conventional cultivation, harvesting is completed by the end of October, and winemaking is largely finished by November, but with secondary induced shoot cultivation, harvesting runs from mid- to late November, with winemaking carried out through the year end, which can be quite challenging.
We constantly gain new insights and discoveries as we explore secondary induced shoot cultivation through trial and error each year.

Suntory volunteers supporting the harvest being briefed on their work procedures. They receive meticulous instruction and a wide range of information concerning not only secondary induced shoot cultivation, but also the ideals of winemaking. This serves to deepen their understanding of winemaking, and raise awareness within the company.

We Aim for the Advancement ofJapan’s Wine Industry as a Whole, Not Only Tominooka Winery

“Wine no Mirai Tominooka Winery Chardonnay Akikaze no Seijuku 2022” was produced with secondary induced shoot-cultivated grapes. Limited edition of 450 bottles. Label signed by Tatsuki Shiga.

“Wine no Mirai Tominooka Winery Chardonnay Akikaze no Seijuku 2022”

Last autumn we released “Wine no Mirai Tominooka Winery Chardonnay Akikaze no Seijuku 2022,” our starting-line wine made with 100% secondary induced shoot-cultivated grapes. These grapes, harvested in 2022, were our first attempt at growing Chardonnay grapes using this technique. We hope that, as the market recognizes the quality of this wine, more people in the industry will take an interest in the technique.
Based on a strong conviction that Tominooka Winery should play a leading role in winemaking in Japan, I want to contribute to the advancement of the industry as a whole, not just that of Tominooka. To this end, I hope to share widely the knowledge and expertise we are gaining in the area of secondary induced shoot cultivation.