Indian RHUBARB (Rheum emido): This ancient plant has many family members in Bulgaria, Asia, China; it has been naturalized all over the world. All rhubarb relatives give some dye color from the stem and leaves, but handle whole plants with care as these parts are toxic to ingest.
Perfect over-dye to obtain unusual colors. Add a bit of alcohol to make this dye powder mix better into a paste. Dye extract in acid bath: rich greenish-browns. Dye extract with oxalic and tannic acids: golden browns. [Asia]