In several literature in China were recorded various species of the indigo genus, but in Chosbn documents, the two have been intensively mentioned, that is, Polygonum tinctorium (PT) and Isatis Tinctoria(IT). Allowing for some slight contradictions of the records between the two countries, we insist that PT is the aborigines historically longer than any other indigo plant in Korea, and that IT is the one implanted from China in late Chosbn period. Indigos can be grouped into two major categories : `ChO˘n` or an indigo forming sediment in the course of making, and `Nam` or the one without. The dyestuffs of blue, or dark blue tineged with red, which had been ocasionally recorded until the mid Choson, could be made from the-species without sediment. The period when the color thus obtained was prevalent can be traced back to the era of Ybngjo, when the import of blue-dyed textiles from China was prohibited to encourage the domestic dyeing industry. However, a more clarification is needed on this matter, since all of the previous researches are arguing, with little validity, that the indigo genus in Korea be PT. Judging from the documents recording that PT did not form any sediment, and that from it was obtained only light color like indigo, it is a matter of re-discussion in terms of botanical taxonomy to define as PT the species being cultivated in some areas in Cho˘llanam-do. In conclusion, a joint research, including specialists in traditional dyestuffs and in botany in relation to the taxonomical problem of the indigo genus, would be expected for further investigation on this matter.