Answer: The dye is actually made from the leaves, not the berries. Interestingly, the juice of the plant is yellow, not blue. The dye is produced by fermenting the leaves, which contain a substance called indican, the content of which is strongest when the plant is in flower. The leaves are steeped in water for 12 to 48 hours with frequent stirring. The dye consists of the blue sediment that settles to the bottom of the container.
Indigofera tinctoria is a shrubby perennial is native to the Malaysian archipelago, and thrives in areas with consistently warm temperatures and abundant moisture. However, the plant, which by the way isn't particularly attractive, can be grown as an annual in cooler regions. Start the seeds in early spring, and plant outdoors after the last frost date.
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