yama-ai 山藍

Lit. "mountain indigo." Perennial plant 30-40 cm high, Mercurialis leiocarpa Sieb. et zuc., used to make a blue dye senryō 染料. Mountain indigo grew in highland areas of central and southern Japan, and the leaves were harvested in summer and early autumn. The leaves or juice was rubbed directly onto fabric giving a light green-blue color known as suri-ai 刷り藍 (rubbed blue). Yama-ai was most important before and during the Nara period, but continued to be used through the Edo period. The dye contained impurities and the proportion of colorant was low, so the dye-color was dull and ran easily.