Dyer's knotweed (Polygonum tinctorum) was the most important blue dye in East Asia until the arrival of the Indigofera species from the south, which yield more dye.
Polygonum tinctorum merupakan pewarna biru paling penting di Asia Timur sampai kedatangan spesies Indigofera dari selatan, yang menghasilkan lebih pewarna.