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About this seed
True indigo (Indigofera tinctoria) is a legume shrub 1–2 m tall with pinnate leaves and pink to violet flowers, grown for centuries as the source of natural blue dye. Its seed coat is hard: scratching or briefly dipping the seed before sowing is what makes it germinate.
Also known as: Indian indigo, Neel (Hindi, Bengali, Urdu), Nili (Marathi, Tamil), Avuri (Tamil), Aviri (Telugu), Amari (Malayalam), Neelinee (Sanskrit), Tarum (Indonesian), Nila (Malay), Indigotier (French), Indigostrauch (German), Indigofera sumatrana (synonym).
Pretreat the seed
- Sand method: mix seed with sand and rub gently to scuff the coat without cutting the embryo.
- Hot-water method: dip the seed in boiling water for about one second only.
- In a published trial, untreated seed germinated 48% and sand-scarified seed 78%. That figure is from another seed lot, not a result for this one.
Sowing
- Use a clean, free-draining mix in a container with open drainage holes.
- Sow about one seed-width deep, water gently and keep warm in bright, indirect light.
- Keep the mix evenly moist, never saturated, and ventilate covered trays.
After pretreatment seed typically germinates within a week (approximate). Seeds with a hard coat can still start at different times, so leave sound ones undisturbed.
Growing on
Give seedlings stronger light and warm, airy conditions gradually. Water when the upper layer begins to dry. Pinch or prune only after a healthy root system and several sets of leaves have formed. The pods are 2.5–3 cm long and hold 5–12 small seeds of about 1.5 mm.
FAQ
Why did my indigo seed not germinate?
The most common cause is an untreated hard seed coat. Scuff it with sand or give it a one-second hot-water dip, then sow in warmth.
Will true indigo grow in a frost-prone climate?
It is native to tropical regions of Africa and Asia, so grow it in a pot under cover where nights are cold.
Can I make dye from home-grown plants?
The dye comes from fermenting the leaves, but this listing is for botanical cultivation only and does not cover dye, food or medicine use.