Sericulture
One of Shirakawa-gō’s primary industries was sericulture: the raising of silkworms to produce silk fiber. Silkworms eat the leaves of the mulberry tree, which grows abundantly in the area, and sericulture was adopted by local residents in part because, unlike rice cultivation, it does not require flat, arable land.
Sericulture took place in the attics of gasshō-style houses, directly above the villagers’ sleeping and living areas. It had a significant influence on the way gasshō-style roofs were designed and built. The steep angle of the roof, for example, provided more space for sericulture, as multiple levels could be added. Meanwhile, the lightweight shoji (paper windows) in the gables at each end could be opened to allow ample light and ventilation for the silkworms. The roof’s thick thatch provided excellent insulation, allowing cultivation even in the summer heat.
The production of silk also created valuable by-products. Perhaps the most significant of these was saltpeter (potassium nitrate), which was used to make gunpowder. To create saltpeter, silkworm excrement was combined with ingredients that included straw, soil, and mugwort, and the mixture was left to ferment for three to four years. It was then refined, and saltpeter crystals were extracted. Saltpeter dissolves in water, so villagers made it in holes near their home’s sunken hearth (irori), where it would not be exposed to rain.
Sericulture is attested in Shirakawa-gō as early as the 1700s. In the final decades of the Edo period (1603–1867), Japan ended its policy of national isolation and began trading with Western countries, during which time silk became a particularly valuable export. Sericulture continued in the village until the 1970s.
The Wada House, located in the Ogimachi area, is the largest gasshō-style house in Shirakawa-gō. It belonged to the Wada family, who made their fortune through the production and trade of saltpeter and silk fiber.
