Plant Dyes – Extension Master Gardener Volunteers of Durham County

By Martha Keehner Engelke, NC State Extension Master Gardener^SM volunteer of Durham County

Interest in natural dyes is undergoing a resurgence as people look for environmentally conscious and sustainable ways to make clothing and household goods. I didn’t know much about the topic but this summer I had two experiences that gave me a beginner’s knowledge about a plant that has been used for centuries to dye textiles: Indigo.

My first experience occurred when I volunteered at the Clover Bud Camp. The camp is a joint venture between the Durham County Master Gardeners^SM and the Durham County 4H program. Children between the ages of 5 and 8 years old learned about “Art in Nature“. One of the sessions was on using indigo to dye fabric.

River Takada, Mixed Media and Fiber Artist, from Durham, North Carolina demonstrates “shibori”, She brought several examples (see the table in the first picture) that illustrate the shibori method. (Image credit: Martha Engelke)

During the class, the children had an opportunity to not only dye fabric but to learn about Shibori, a traditional Japanese method that involves folding and binding the fabric to create patterns when the fabric is dipped in the indigo. River mixed the dyes in large buckets using indigo that had previously been extracted from the plants. Extraction is a process that requires a large crop of indigo and a lot of time (several weeks).

The second experience was attending a workshop offered through Piedmont Fibershed, a nonprofit organization dedicated to building a regional fiber system centered around local fibers, local dyes, and local labor. This workshop was led by Bethany Joy Hebbard and the focus was on growing and using fresh indigo leaves rather than dye that had been previously extracted from plants.

The History of Indigo

Indigo was used in China 3,000 years ago and in Egypt more than a thousand years before that. The most common uses were to dye textiles or make cosmetics. However, indigo has also been used for medicinal purposes. Neurological disorders, dental problems, inflammation, and skin diseases have been treated with indigo and indigo is thought to have antimicrobial properties and aid in the healing of burns.

In the United States, indigo became a commercial crop in the 1740’s and was grown on plantations in South Carolina, Georgia and Florida. Growing indigo was a very labor intensive process. In 1870, two scientists in Germany (Adolf von Baeyer and Adolf Emmerling) synthesized indigo which led to a significant decrease in the growing of natural indigo. Although synthetic indigo still dominates the market, there has been a resurgent interest in natural indigo dye because it is more sustainable and environmentally friendly.

The precursor to indigo is indicin which is found in the leaves of the plant. Through a process of oxidation and fermentation the indican is transformed into a blue, water-insoluble indigo dye. The most common colors associated with indigo are blue and green but by using heat during the extraction process it is possible to activate another chemical (indirubin) which will produce red and earth tones. Although many plants are used to dye textiles, one of the advantages of indigo is that it doesn’t require a mordant (fixative) as long as the cloth is scoured (treated with soda ash or sodium carbonate) before applying the dye.

There are varieties of indigo from China, Guatemala, and other tropical environments. These varieties vary considerably in their indigo content. The variety that is most often used to dye textiles is Japanese Indigo (persicaria tinctoria) because it yields the most dye.

**Growing Japanese Indigo (persicaria tinctoria)**

Persicaria tinctoria (also known as polygonum tinctorium) is a member of the Polygonaceae family. It is hardy in zones 10-12, but in our area it is considered an annual. Seeds can be started indoors 4-6 weeks before the last average frost. The seeds should germinate within two weeks but occasionally it takes a month. Seeds can be harvested from existing plants but it is unlikely that they will germinate after the first year and long-term storage is not recommended. Seeds can also be sown directly outdoors after the threat of frost has passed. They grow in any soil but clay loam seems to be the best. Adding a bit of guano or cow manure to the soil enhances growth and using a nitrogen fertilizer during the growing season is recommended. Few diseases affect the plant but it does do best in the sun with regular, frequent watering. Remember, it is basically a tropical plant.

Persicaria tinctoria can be grown from seed or cuttings. The first picture was taken in an outdoor garden while the second is a potted plant grown from cuttings. The third picture illustrates the leaves and flower. (Image credit: Left: I Naturalist UK, CC-BY-NC; Middle and Right, Martha Engelke)

Persicaria tinctoria is also very easy to propagate from cuttings, which is what I did. The workshop was held in July and it was too late to grow the plants from seed. Bethany had a field of plants which she shared with us. I took several cuttings, put them in a pot indoors, gave them plenty of water and sunshine and they have done well. I found that they do need to be watered at least every 1-2 days.

Once the plants are established, you can harvest the leaves 2-4 times before they flower and set seed in mid to late September. Once they have set seed, the amount of indigo in the leaves is greatly reduced. To harvest the leaves, cut the plants plants about 6-8 inches from the ground leaving a few leaves at the base. Keep them moist and use them within 24 hours if you are planning to use them for fresh leaf dying.

Fresh-Leaf Indigo Dying

Before using the leaves, it is important that the fabric is scoured (boiled with soda ash at a concentration of 1-2% of the weight or the fabric) for 30 minutes and then soaked in soy milk. This will help to remove natural gums and waxes and “fix” the dye especially when using bath methods.

There are two ways to dye with fresh indigo: abrasive methods and baths. The abrasive method is easy and straight forward. Using dry fabric, one can hammer (Tataki zome) the leaves once they have been affixed to the fabric with packing tape or you can use a stencil.

In the stenciling method, after stabilizing the fabric, affix the stencil to the top of the fabric. Then, take 4-5 indigo leaves and stack them so they look like a cigar. Keep refolding and replacing leaves as your leaves disintegrate. It is best to use a stencil made of hard plastic or wood rather than one made of cardboard. Contrary to what I thought, stencils with smaller spaces rather than ones with wide open spaces worked better.

The bath technique includes several methods. You can make a salt marsh by sprinkling a few teaspoons of salt over a bowl of fresh leaves and then use your hands to agitate the leaves until the liquid is released. Continue to do this for 10-15 minutes or until the fiber stops getting darker. Rinse the fiber in cool water and dry out of the sunlight.

Another bath approach is to place your indigo leaves in a blender and fill it about halfway with cold water. Blend until the mixture is frothy. Strain the mixture over a tea towel and squeeze the liquid into a bowl. Submerge the cloth for about 15 minutes, stirring if needed. You can repeat the process if you want a deeper color. Dry the fabric out of direct light. Although indigo is not toxic, I chose to wear gloves because the dye is a bit difficult to remove from your hands.

The first sample was created using the stenciling method, the middle picture represents the hammering method and the samples in the picture on the right were made using a bath. (Image credit: Martha Engelke)

Using fresh indigo to dye fabric has many advantages. It is a low cost, straightforward process that can be completed by an individual or it can be a fun project with children. You need only a few plants and resources. Of course there are constraints. It is a seasonal activity and after my plants go to seed, I will have to wait until next year to grow more fresh indigo (although I am going to see if I can keep it growing as a house plant). To get the best results, you need to work fairly quickly and especially with the abrasive methods, the results can vary based on how well you are able to hammer or the type of stencil you use. The results will also vary depending on the freshness of the indigo. If you wait until the plants start to set seeds, your results may be disappointing. However, I am dye-ing to try it again!

My first project with fresh indigo using a stencil. Next project? Deciding what to fill them with and who to give them to!

Image credit: Martha Engelke

Resources and Additional Information

This article summarizes the historical and cultural background as well as the identification distribution and uses of indigo.

https://edis.ifas.ufl.edu/publication/EP642

If you are interested in growing larger amounts of indigo and extracting the dye for use in bigger projects, the story of how an artist in South Carolina did this is inspirational.

https://sc.edu/uofsc/posts/2022/11/carolinian_indigo_harper.php

Susan Dye (appropriate name, right?) has experimented with growing different varieties of Japanese indigo as well as other indigo plants. She shares the results of her experimentation on her blog and discusses the sociopolitical implications of the resurgence of indigo dyeing.