Indigofera tinctoria, commonly known as True Indigo, is a tropical legume historically used for thousands of years as the primary source of indigo blue dye. It is a tender perennial grown as annual in cold climates, reaching 2-3 feet tall with pink to violet flowers.
Before sowing
Seeds have physical dormancy with hard seed coat. Without pretreatment, germination is very low (6.7%). Mechanical scarification (light rubbing with sandpaper for 5 minutes) yields 67% germination.
Sowing
What to expect
Tips
Start seeds indoors 4-8 weeks before last frost. Provide temperatures of 70-75°F. Plant seeds 1/4 inch deep and tamp soil. Germination is low and irregular without scarification. Use larger pots as the plant has a delicate taproot that is difficult to transplant. Keep soil moist but not waterlogged during germination.
Sources: Pinetree Garden Seeds, Sheffield's Seed Company, Gardening Know How, Kristin Arzt (indigo dye guide), World Seed Supply, Electric Veg, ResearchGate studies
