The inside story of the Winter-sweetened Technique: its development and extension

The Winter-sweetened Technique (WST) was developed at the Tohoku National Agricultural Experiment Station in the early 1990s. In the WST, cold winter air is let into greenhouses in northern Japan to make Nappa taste better and richer in nutrients. Nappa is a generic name of Japanese leaf vegetables such as headless Brassica, spinach or chrysanthemum with a length approximately 25 cm, and mainly eaten boiled. The WST operation is quite easy for farmers, opening doors and side films of greenhouses when Nappa has been grown to the marketable size. However, unexpected problems had come out after the extension started. As a member of its developers, I recorded the inside stories in this paper to consider the relationship between technical developments and extensions. In the WST, low temperature exposure for one to two weeks enriches sugar and functional components in Nappa, and changes the shape of its leaves to rosettes. Traders disliked the shape, however consumers prefer it due to the excellent taste. Convinced by consumers’ acceptance, we made efforts to inform them that the rosette shape is the proof of WST. Gradually, farmers started to produce WST Nappa, and distribute it in small local markets. The WST was featured in programs on TV and articles in newspapers. In 1999, a seed company introduced to farmers and traders a cultivar of the rosette shape produced even in higher temperatures. Production of the so called WST Nappa increased rapidly, and it was supplied to markets in Tokyo. However, these farmers with less understanding of WST could not continue to open their greenhouses through the days for enough time. The Nappa lost the WST qualities. The situation has continued until now. In other areas, high quality WST Nappa has been produced using normal cultivars by farmers with their good understandings of the WST.