Japanese Indigo
Persicaria tinctoria
Annual
DYE: Indigo blue, robin’s egg blue
 
GROW: Direct seed 4-6” apart in full sun after the last frost date OR start indoors 6-8 weeks before transplanting outside in full sun. Keep ground moist. Once established they quickly grow to 12-18”. Shade cloth is recommended for best leafy growth and to preserve soil moisture. Succession planting is recommended to maintain a steady supply of vigorous leaves, the source of indigo dye. Potency of the dye diminishes once the plant produces flowers. Good for container gardening.
 
HARVEST: Harvest leaves early in the morning. Use immediately for fresh leaf Indigo dyeing, or dry and store in an open paper bag for future use in a dye vat.
 
EXTRACT DYE: Indigo is in a dye class of its own, as its pigment is not water soluble and requires making a “vat”, either by fermentation or with the aid of chemicals. The recipes to achieve deep indigo blue are too complex to describe here – please refer to published processes that can be found online or in natural dye books. However, you can achieve lighter blues without making a vat by 1) mashing the fresh leaves and massaging the color into the fiber, or 2) blend fresh leaves with very cold water and immerse fibers. Protein or cellulose fibers may be used, but the best depth of color with fresh leaf methods is achieved on silk. Indigo does not require a mordant.