Ryukyu Ai is a perennial plant in the Kitsunenomago group. Indigo dye is made from the fermented leaves of this plant which is native to Okinawa.
Ryukyu Ai is different from other Japanese Ai, and comes from a different plant group, also does not use sukumo. Many considered Ryukyu Ai is the most beautiful blue in the world.
The basic raw material is the leaf of the Polygonum Tinctorium. The Japanese process differs from that in other parts of the world in that the leaves are fermented to extract the indigo compound.
The plant grows well in the western part of Japan (mainly Tokushima = old name, Awa.) Using sukumo (fermented Polygonum leaves = composted leaves) doesn’t provide any shortcut to the rest of the dyeing process.
Compared with other Indigo dyeing methods, the Japanese way requires more sensitive care throughout the process because they have to keep the bacteria alive through the entire dyeing session. The Japanese words some and zome mean dyed.