Indigo (Indigofera tinctoria) has been in use as both a medicinal and a dye plant for so long that it is uncertain where it originated. The plants have naturalized throughout tropical Asia and parts of Africa. Both the Greeks and the Romans imported the dye from India. The word “indigo” comes from both the Greek and Latin words that meant “from India”.

Indigo was introduced into Europe in the 17th century where it directly competed with the native woad, which also produced a blue dye. Eventually, the Europeans used both, sometimes in combination. Dutch and Portuguese traders made a fortune importing indigo from India. When the British began expanding their empire, they introduced indigo to the New World and started growing it in the Caribbean.

Long known in the West as a dye plant, indigo has been used for thousands of years in Chinese medicine to reduce fever and inflammation and to purify the blood and the liver. The Egyptians, Greeks and Romans used it on wounds and sores. It has also been used as an emetic because ingesting the plant causes nausea and vomiting.

It is the leaves that contain the components of the dye. They are soaked in water which leaches out the indican which is colorless. Contact with the water turns it into indoxyl which is not soluble in water nor will it be absorbed by yarn or fabric. You need to add a reducing agent. Originally dyers used stale urine but in modern times we use Spectralite or RIT Color Remover. Soak your dyed fabric or yarn for 20 minutes in the reducing agent. When you remove the fabric, it will turn blue as the dye reacts with the oxygen in the air. The longer you soak it, the deeper the blue color.

Indigo is a legume which means that it can fix nitrogen in the soil. If you live in zone 9 or warmer, you can use it as a cover crop in your vegetable garden to replace nitrogen in your soil that was depleted by your vegetable plants.

Indigo is perennial in zones 9 through 12. The rest of us grow it as an annual. It needs full sun and well-drained soil. No fertilizer is necessary because it produces its own nitrogen in the soil. The plant is a shrub that grows 3 to 6 feet tall. If you are growing more than one plant, space them 4 to 5 feet apart. The flowers look like pea flowers. They are pink or violet and appear in the late summer.

If you want to start your plants indoors, start them 8 weeks before your last frost. Soak the seeds overnight and then plant them ½ inch deep in individual containers. You can transplant your seedlings outdoors after your last frost when the temperatures are consistently 70⁰F – 80⁰F. Space them 4 to 5 feet apart.

You can start harvesting the leaves when the flowers begin to appear, starting with the lower leaves. You should be able to harvest every 2 weeks until the cool temperatures of fall kill the plants.