Natural Dyes from the BTR of Assam: Ethnobotanical insights and standardized evaluation of dye stability

Abstract

Background: The BTR region of Assam lies in the trans-border area adjoining Bhutan and forms part of the foothills of the Eastern Himalayas. It is inhabited by several ethnic tribes who have traditionally woven their ethnic garments and used plants as sources of natural dyes since time immemorial. Despite their cultural and ethnobotanical significance, systematic documentation and scientific evaluation of dye-yielding plants from this region remain scarce. This study addresses this gap by documenting traditional knowledge and characterizing dyes extracted from regional plant species in terms of their color yield and thermal stability.

Methods: The study was conducted between December 2024 and March 2025 across 15 locations situated within the three districts of BTR, Kokrajhar, Chirang and Baksa, of Assam, India. Primary information was gathered via semi-structured interviews and informal discussions with 30 purposively selected informants who were local weavers, industrial dyers, or resourceful custodian of traditional knowledge system. Collected plants were processed for dye extraction and tested for color yield, heat stability, and dye performance. Each species was assigned a dye score based on color strength, solubility, and stability, while conservation status was assessed using IUCN Red List categories.

Results: A total of 42 plant species from 31 families were documented. Malvaceae and Fabaceae were the most prevalent families. The study identified 21 distinct dye colors, with yellow (18.75%), cream (15.63%), and red (14.58%) being the most common. Approximately 63.64% of the dyes exhibited heat stability, with yellow and brown dyes demonstrating the greatest stability. Plant parts utilized for dye extraction included leaves, flowers, roots, bark, and fruit. Dye scores ranged from 24 to 84, reflecting a spectrum of dye performance. Notably, Hibiscus x rosa-sinensis L. and Hibiscus sabdariffa L. achieved the highest dye scores of 84 and 78, respectively.

Conclusions: The study highlights the rich diversity and ethnobotanical importance of dye-yielding plants in the BTR. Several native and cultivated species demonstrated promising dye potential for sustainable, eco-friendly textile applications.

Keywords: Natural dye; Dye-yielding plants; Ethnobotany; Indigenous practices of dye; Dye score