Indigo Plant Harvest – Tips On Picking Indigo For Dye

Indigo Plant Harvest – Tips On Picking Indigo For Dye

By: Teo Spengler

Many of us are familiar with the beautiful, faded-blue hue made famous by the indigo plant. For years, cultivators used an indigo plant harvest to make a dye used extensively around the world. It was the first dye to color Levi jeans. Although the popularity of the natural dye stalled when a synthetic dye was developed, picking indigo for dye is making a comeback. If you want to learn how to harvest indigo to make your own dye, read on. We’ll tell you how and when to pick indigo.

Picking Indigo for Dye

Indigo plants have lovely flowers, but it is the leaves and branches that are used for dye. Although there are many varieties of indigo, it is true indigo (Indigifera tinctoria) that has traditionally been used for dye.

Note that neither the leaves nor the stems are blue. The blue dye comes out after the leaves are treated.

When to Pick Indigo

Before you jump into harvesting indigo, you have to figure out when to pick indigo plants. The ideal time of year for picking indigo for dye is just before the blossoms open.

When picking indigo, remember that these are perennial plants and need to continue to perform photosynthesis to survive. To that end, never take more than half of the leaves in any one year. Leave the rest on the indigo plant to allow it to produce energy for the following season.

Once you have completed the indigo plant harvest, act promptly. You should use the harvested indigo as quickly as possible after you finish picking the plant for dye.

How to Harvest Indigo Plants

When you are harvesting indigo, you need to collect the leaves first. Many people simply bundle leaves and small branches for processing.

After you’ve gathered your indigo harvest, you’ll need to treat the foliage to create the blue dye. Preferred techniques vary. Some who cultivate indigo for dye suggest you start by soaking the leaves in water overnight. The next day, mix in builder’s lime to achieve the fade blue coloration. Others suggest a composting method. A third way to extract the dye is by water extraction.

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Growing & harvesting Indigo (Indigofera tinctoria)

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Cultivation of Indigo (Growing Indigo)
Indigo plants love warmth and humidity. To grow indigo in a cold country, you need a warm greenhouse, a conservatory or a sunny windowsill. Providing you can keep the plants warm, the earlier you sow indigo seeds the better, as you will have a longer growing season. I try to sow mine in early February, but you can sow indigo seeds as late as April.

Soak the seeds overnight in water and then sow your seeds in pots at least 3 inches in diameter, one seed per pot (pots are better than seed trays because indigo does not like to have its roots disturbed). Keep the pots in a heated propagator until the seeds germinate and then move them to warm windowsill. When the indigo seedlings are large enough, re-pot them once or twice into larger pots with good soil. Eventually use a 10 litre pot per plant. If you have a sheltered position and the weather is warm you might be able to keep the plants outside in the summer.

Indigo plants are hungry feeders and need feeding almost as often as tomatoes. Well cared for plants can grow 2 metres tall and might need pruning.

Spray the plants with water from time to time and if possible keep them on a pebble tray to increase humidity. Keep checking greenhouse plants for red spider mite, which may be a sign that the humidity is not high enough.

Harvesting Indigo dye
The best time to harvest is just before the flowers open. Indigo is a perennial plant and to keep the plant for more than a year you should harvest only half the leaves at one time.

Your indigo plant may need to be more than a year old to come into bloom and it needs plenty of warmth to flower. Try to keep it alive over the winter which should give you an early start the following year. Do not feed the plants from October to March, prune them to a manageable size, reduce watering and keep the plants warm.

Extracting Indigo Pigment (indigo dye)
Use the leaves as soon after harvesting as you can, and follow the instructions for extracting indigo dye from Japanese Indigo. If you have a large enough pot to soak the indigo you can use chopped branches, otherwise pluck and use the leaves.

According to Buchanan, 500 grams of indigo leaves will give you enough pigment for approximately 100 to 200 grams of wool. This varies with weather, soil and age of the indigo plant.

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False Indigo requires very little maintenance. Keep it watered regularly for the first year. Once established, Baptisia is very drought-tolerant.

Your Baptisia plant will bloom from late spring through early summer. Although in most areas it dies back to the ground in winter, False Indigo leaves turn an unattractive black with the first hard frost and the plants tend to collapse by mid-winter, so cutting them back in fall is usually recommended. False Indigo is a member of the pea family and you will notice the resemblance in its foliage and flowers, as well as its fondness for cooler weather and its tolerance to humidity.

Indoors or outdoors and growing for seed

Growing in a greenhouse it was possible to plant the seedlings out earlier but even then a mild frost in early May damaged and killed some of the plants.

Frost damaged seedling in the greenhouse in May 2016.

Japanese indigo does not need to be grown in a greenhouse or polytunnel unless you live far to the north but it clearly prefers being indoors growing lushly with greener, larger leaves and does not produce flowers until later so has a longer season.

Japanese indigo needs a long growing season to flower and usually only comes into full flower in October. It is self-fertile so will produce seed in a sealed greenhouse but will flower sooner outside in full sun. However, If frosts or bad weather are forecast before the seed has set be ready to dig a few up and transfer to greenhouse or poly-tunnel or bring indoors in pots. In the North it may be best to grow Japanese Indigo in a greenhouse or poly-tunnel. But because it flowers later it may not be possible to get seed unless the greenhouse is heated.

Some growers have reported that it is possible to get plants through the winter by bringing them into a well-lit and warm area where they will flower early the following year and produce seed.

The different varieties of indigo respond differently to greenhouse growth as the photo below shows. This particular variety flowered at much the same time in or out of the greenhouse. The leaf curl may be a response to the extra heat.

The long leaved variety growing in the greenhouse with curled leaves.

This miserable looking plant flowered in June and as you can see has been highly stressed with stunted growth and pale leaves with a pinkish blush

There are always a few plants that come into flower before the rest and it is best to leave these alone when you harvest. A few years ago I began an experiment to try and breed a variety of early flowering plants so I could be sure of getting some seed even in a bad year. This went according to plan and I ended up with plants that flowered in early September and some in August. However, once the plants start to flower the amount of indigo in the leaves starts to reduce and in full flower the yield is very poor. This led to lower harvests overall. Another strategy you can use for getting seed is to grow a few plants in a dry bed only giving them enough water to keep them alive. These plants will become stressed and will flower earlier – they may look miserable but the seed will produce nice healthy plants next year. Interestingly when the plants are in full flower they are very attractive to bees particularly honey bees. I wonder if honey can be obtained from the German fields of Japanese Indigo, as is possible with the fields of Woad in Norfolk.

Seeds from the flowers in the greenhouse. As bees and most pollinating insects could not get into the greenhouse it looks like the the flowers are self fertile.

When the flowers go brown they can be cut and hung up or laid out to dry and some of the seed will fall out. The remainder can then be rubbed out. Separating the seeds from the “chaff” is a skill all by itself. Once you have removed the seeds and dried flower material from the stalks, place the whole lot in a tray and shake from side to side. All the heavy seeds will settle to the bottom and if you are careful you can blow the chaff from the top. This can be a dusty business so you must be careful not to breath it in. Some of the seed will retain an outer layer of brown chaff bound to the seed this does not impair germination.

Take a few handfuls of leaf and crush them up in a suitable container or blender. Add some white fibre immediately to the mix and leave for an hour. The colour obtained is rather dull and some of the colour may wash out. What remains will be fast and will give you a good indication of how good your indigo is.

When new to dyeing with Japanese Indigo and Woad it is common to wonder how indigo was discovered as the plants apparently do not produce anything obviously blue though occasionally leaves will die and turn a dark grey or blue black. I suspect that someone observed that when crushed the fresh leaves will release indigo but it is only noticeably blue if you then add some white fiber to them. This is a good test to see if your indigo is ready to be harvested.

Watch the video: How to Prepare an Indigo Vat