The indigo produced in Tokushima prefecture is called Awa-ai. It has been cultivated in the Yoshino River area for a long time. By the mid-Edo period (eighteenth century) Awa ai was sold thoughout the country as a dye for cotton largely used for commoners’ garments. Until about 1898 Awa area boasted the largest output of indigo in Japan, accounting for about a quarter of the whole national production. Advantageous effects of dyeing with natural indigo include its repelling insects, deoderizing, and strenghtening the fabric.