The preferred variety for dye. A tender annual, indigo thrives in fertile soil and likes heat and humidity. When the plants have grown 1' - 2' tall and bruised leaves turn navy blue, they are ready for a first harvest. If you cut the stems several nodes up from the ground, they will re-sprout and you can harvest regrowth, perhaps several times more. Best started indoors 6-8 weeks before last frost, transplanted out on 1ft centers and kept moist.
Plan ahead and prepare the dye bath the same day as the harvest. Soaking the seed for 24 hours increases germination success. Annual.