Tsurubami is the old name for sawtooth oak, which belongs to the genus Quercus of the Fagaceae family, and the color dyed with the acorns and bark of the tree is called 'Tsurubami-iro'.

Sawtooth oak grows wild in various places south of Honshu, and because it is durable in dyeing, in ancient times it was used as the color of the clothes of the common people.

The characteristic of dyeing with horsegrass is that the color changes depending on the mordant. If it is plain dyed, it becomes a flaxen color, if it is dyed with lye, it becomes yellowish, and if it is iron mordant, it becomes blackish.