Sustainable Cultivation of Plant-derived Indigo for Diversification and On-farm Value-added Dye Pigment Production

Final Report for FS10-241

Project Type: Farmer/Rancher
Funds awarded in 2010: $9,871.00
Projected End Date: 12/31/2011
Region: Southern
State: Tennessee
Principal Investigator:
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Project Information


A comparison of indigo yielding plants showed that varieties of Indigofera tinctoria, Indigofera suffruticosa and Persicaria tinctoria can all be grown in Middle Tennessee. The I.tinctoria and I.suff were both difficult to germinate in greenhouse starts and difficult to direct seed, resulting in fewer established plants in our study. Initial indigo extraction data for P.tinctoria indicates a range of variables impacts final pigment color, including growing and processing conditions and stress conditions during plant growth. Preliminary dried indigo quality results in successful pigment extraction batches showed approximately 2-3% indigotin content, although more research on successful growing and processing is needed to yield consistent results.


Natural dyes are plant and earth-based materials that can be used for dyeing textiles, foods and other industrial uses. In addition to the use of fresh plant material, there is a market for both dried plant madder, or powders and concentrated dye liquors made from fresh dye plant material, whether leaves (indigo), flowers (marigold, weld), or roots (madder). These storable, easy to ship materials are becoming increasingly popular among home dyers due to their safety, ease of use and environmentally friendly characteristics. We believe that with the appropriate processing, the plants can be turned into commercially viable extracts for industrial dyeing. In addition to providing a source of year-round income, natural dye crops can increase sustainability in a diversified cropping system, by increasing leguminous plants, beneficial insect habitat, and perennial crops. Thus, they are a potentially viable cash crop for Tennessee growers.
However, in order to move natural dye crops into the wider market, including commercial and industrial applications, we must find cost effective and logistically feasible ways to grow and process the plants into a value- added pigment or extract form. In order to increase the customer base for natural dyes, we must determine the best ways to turn raw plant material from the agricultural commodity into an easier to use industrial pigment. This includes an investigation of how to produce the raw plant material so the yields of pigment are highest, as well as determining the optimal processing techniques. Finally, in the case of direct sale of pigment or dye to artisan or craft customers, it may be important to the growers to have appropriate technology to allow for on-farm processing, allowing for farm to dye traceability so end consumer may be able to know which farm grew their dyes. Small scale processing has been shown to be economically viable in many agricultural industries where product differentiation is important, such as specialty cheese processing. While there may be a small local market for fresh dye material, without the processing stage we expect the market to be greatly limited, as well as season limited instead of year-round.

The focus of this SARE study was on plants containing blue dye pigment, or Indigo-containing plants. In our past experience, several indigo-containing plants are low nutrient feeders and have few pest problems. For example, the indigo-containing plants in the Indigofera species are leguminous plants that frequently serve as a green manure and a summer cover crop in the tropics due to their nitrogen-fixing capabilities. A major goal of our research was to determine if these nitrogen-fixing indigo plants can be successfully grown in Tennessee.

Increasing crop diversity through natural dye plants also allows growers, especially those with diversified vegetable cropping systems, to capitalize on different farm labor throughout the year. Most of the dye crops offer once or twice-a-year harvests instead of the few times a week harvests as market vegetable production can require. Indigo, for example, can be harvested in July and October in Tennessee if seedlings are established by Spring. Potential methods for processing include a fresh leaf precipitation method (the subject of this study) which takes 2-3 days and a dried leaf composting processes which can take up to 100 days and is labor intensive without specialized equipment. The dye precursor for indigo is found in the leaves or leaflets.

There are currently 3 varieties of commercially grown indigo plants, including Indigofera spp, Persicaria tinctoria (Japanese Indigo, formerly called Polygonum tincotirum, Ai species), and Isatis tinctoria (woad). The blue indigo pigment shows perhaps the most potential because of its recognizable blue shades and the fascination value of the story behind indigo and thus was the subject of our research. In addition because of the complications of processing the plant it has the least information available to growers.

Selling indigo processed into a high quality and consistent extract to the commercial manufacturing sector (dyehouses) would likely be the largest potential market in terms of volume. This market is not yet developed but there is believed to be an interest, especially among manufacturers looking for an eco-friendly or domestic source of dyes.

In addition to selling into the industrial pigment market, there is likely a more immediately accessible market for dyes among artisans and craftspeople. In an Internet-based retail setting, unbranded, conventionally grown (non-organic), natural indigo powder currently sells for between $46 (The Dyeworks, CO) and $60 (Earth Guild, NC) per pound. Research suggests yields of 60lbs/acre of indigo yield for Indigofera species, thus garnering between $2760 per acre and $3600 per acre of indigo after processing. However, an Italian research project in a climate more similar to the Southeastern US shows yields of up to 326 kg/hectare, or 290 lbs/acre of Indigo from the Persicaria tinctoria (Angelini, et al. 2004). This would result in approximately $13000/ acre. According to a 2004 European Union endorsed research team called the Spindigo Project, woad can produce indigo in quantities of approximately 50 kg/ha or 44 lbs/acre. Woad powder currently retails on the internet for 40g/25 euros (Bleu de Lectoure) or 20.50 British Pounds for 20 g (Woad-inc). These sell for much higher than we think our market could currently bear in the Southern US, at an equivalent of $635 per pound (given a 1.4 Dollar to Euro Exchange rate and marketing in very small quantities), which would garner $27,966 per acre for woad. These extremely high value products are the result of branding, marketing and EU customer desire for the historic dye of their region. The indigotin (pigment) concentration of woad is only ¼ that of the Indigofera species, making it less productive from a yield of pigment per acre basis, and so it was not included in our study. However, it does show how small farms or a cooperative of farms can be profitable in this niche market with the right branding and a willing market.
As an example of a premium going to a branded, naturally dye extract, Woad-Inc a British company selling locally-grown woad pigment, sells pigment in quantities of 20 g for $20.50GPB, or $34 USD. This is equal to about $2.64/g compared to the average price of unbranded indigo pigment selling for approximately $60/lb (454g), or approximately $0.13/gram for the commodity (Table Rock Llamas, Colorado). The Woad-Inc. product is not certified organic since it uses a pre-emergent herbicide, but the marketing of the product does focus heavily on the story behind the one farm that grows the crop.
There are currently branded natural dye extracts grown in France (Couleurs de Plantes), England, (Woad-Inc), India (Colors of Nature), and several other small scale projects around the globe, with US natural dye distributors carrying these lines. However, there is no US grown or sourced line of natural dyes sold at any appreciable volume.

There is a long history of indigo growing in the South United States. Indigo was one of the top three exported cash crops in the 1700s. We know from historical research that three varieties of Indigofera were commonly grown in the deep South: Indigofera caroliniana Mill, I. tinctoria L (French indigo), and I. suffruticosa Mill. (Guatemala Indigo). Most indigo production throughout the 16th and 17th Century Colonial America occurred in South Carolina plantations, where it was found on dry high ground. The amount of indigo exported from South Carolina increased from 138,118 pounds in 1748 to 1,107,660 pounds in 1772, shortly before the American Revolution, mostly for export to England for fabric dyeing. During this time, Georgia exported 55,380 lbs. The first synthetic dye, isolated from a coal-tar, was created in 1856 and rapidly synthetic versions replaced the market for natural color compounds, as well as the amount of indigo and other natural dyes grown in the US and abroad. However, the beauty and vibrancy of natural dyes cannot be replaced and it is our belief that the emerging environmentally-aware fashion industry will desire and purchase sustainably-grown natural dyes rather than the petroleum and coar-tar derived synthetic dyes currently used in industry.

Project Objectives:

Southeastern growers need research to determine suitable natural dye crops for our region, and to establish best practices for cultivation and processing of these plants. This project’s goals were to provide a baseline of cultivation, production and cost data for working with the three most promising indigo-containing plants specifically tropical indigo (Indigofera suffructosa and Indigofera tinctoria), and Japanese indigo (Persicaria tinctoria) to create storable, value-added dye products that can be sold from the farm-gate across the region as a natural alternative to synthetic indigo. In addition to assessing the production techniques that yield the highest quality pigment, we made some preliminary post-harvest handling and processing assessments. We explored techniques for on-farm processing of indigo-containing plants into both powdered natural indigo and indigo ‘sludge’.

The ultimate goal of this research project was to establish which indigo-containing plants will grow best in our region of Middle Tennessee, and how they may be best processed to yield products of high market value. Another initial objective was to determine what the best conditions were for growing the different varieties. We planned to measure green harvest weight per variable condition to asses overall green plant yield. We then sought to isolate the pigment from the indigo plant matter through the precipitation method and measure overall sludge weight, dried weight of precipitate, and percentage indigotin content in precipitate. Our goal was to determine whether indican-containing plants can be grown and are likely to be profitable and successfully grown in our region. We also worked to standardize our processing technique to determine the way this project can be scaled onto other farms without specialized processing or cultivation/harvesting equipment.

The research trial involved growing and processing 100 row-feet of each of the three variables of the three indigo varieties utilizing organic practices. Where applicable, we used varying fertilizer/nutrient input variables. We wanted to determine the most suitable methods for cultivating the selected crop(s), based not only on green vegetative yield but also isolated pigment yield after extraction of the indigo pigment. Indigo’s market value is in powder form, so the weight and purity of indigo pigment is ultimately the most important thing. By investigating different nutrient regimes, we sought to determine maximum profitability based on the volume and purity of final product (pigment) yield after taking into account input costs.
Following our 2010 growing season in which Indigofera had very poor germination, we decided to extend our grant time frame for one year and run a small seed germination trial to add to the final report. In Spring 2011, we ran two I. tinctoria germination trials to determine the best strategy for starting Indigofera species from seed, one in March and one in May. The trial has heat, scarification, and soaking variables for the seeds so we can find out the best means way for starting these seeds. Seed starting trails for I. suff. was not possible because all of the seed suppliers were sold out for 2011.


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  • Alesandra Bellos
  • David Wells
  • Eric Wooldrige


Materials and methods:

In 2010, the year of the cultivation and yield study, we ran our indigo trials at Sulpher Creek Farm, a private farm that is part of the Bells Bend Farm. Our originally intended farm site, at George West’s Whopping Crane Farm in Bells Bend was dramatically flooded on May 1-5 in a 500-year flood event, leading us to change farms. Eric Wooldridge, farm manager at Sulpher Creek was a great help in both quickly helping us prepare new ground for the study as well as letting us host our field day events as his farm. The chosen site was a non-irrigated site at the top of a hill overlooking the production vegetable beds of Sulpher Creek Farm. Sulpher Creek is primarily a 80-family CSA and market garden vegetable farm. Adjacent to the indigo crops were other natural dye rows, such as marigold. Potatoes and sweet corn were grown in the neighboring field on the upper field. Vegetable beds are in the lower field under drip irrigation, however no water source was available at our site. We had to truck water up the hill and hand water which was a very high labor cost. The soil test showed sufficient levels of P and K, no soluble N test was available. Our seeds were started under heated, florescent light conditions in March 2010 and potted up and moved to an unheated greenhouse in May 2010. Our outdoor plantings were greatly delayed due to extreme flooding and wet conditions across Middle Tennessee.
For the leguminous crops, both I.suffruticosa and I. tinctoria, the trail was planned as follows: 1) No Input/Innoculant and 2) Compost/Innoculant

For the P. tinctoria, the 4 row trial is as follows:1) Composted manure, 2) Fish emulsion, 3)no-input, 4)no-input (this was going to be a mulch variable but we changed the study, feeling it was critical to mulch due to the dry conditions).
By investigating different nutrient regimes I wanted to determine maximum profitability based on the mass of green leaf yield and purity of final product (pigment) yield after taking into account input costs.

Research results and discussion:
Research Outcomes

Due to different germination rates and severe weather conditions (i.e. a 500 year flood in Middle Tennessee leading to us moving farms) the Indigofera varieties did not established at the same rate as the P. tinctoria. This lead to a lag time in planting as a second and third round of starts were necessary in 2010. After establishment, both the I. suff and eventually the P.tinctoria were more susceptible than I. tinctoria to deer and cattle browse when the electric fence broke down in mid-summer (this was a new field that we moved to early in the season). Due to problems with the fencing, we learned young I. suff was most desirable to both deer and cow grazing, creating 100% loss of this crop. At full growth (approx 3-4 feet) I. tinctoria was completely resistant to cow grazing, perhaps because of its woodier stalk. P. tinctoria was top or heavily browsed by cows that escaped into our fields later in the season (at full growth). Our estimates put livestock damage on P. tintoria at about 70%, concentrated on the P3 and P4 variables of our test plots. This livestock damage potentially created an interesting stress result mentioned in the section called “conditions for indigotin testing.”

There were only 15 I. tinctoria plants which survived after the late seedling establishment and dry weather without somewhat variable irrigation. We dried the leaf matter from half of the plants rather than doing the wet precipitation processing. This was because we felt the volume of leaf matter was too low to run a large enough precipitation vat and we would be better off trying the composting method on these dried leaves. The other half of the plants we dug up and stored in a greenhouse over winter to plant the following season and to save for seed.
See Table 1: 2010 P. tinctoria research outcomes

P. tinctoria pigment extraction, processing conditions, and processed sludge yield

After harvest, dyeplants must be processed in order to obtain the usable, storable blue pigment indigotin. For the purposes of our research, we extracted pigment from the Persicaria using a “wet precipitation process” adapted from a method used historically in Okinawa, Japan. In this precipitation process, harvested Persicaria plants are soaked, leaves still on the stems, in large tubs filled with warm water. As the leaves sit in warm water, they release indican, an indigotin precursor, which is converted to indoxyl and glucose through continued soaking. After the plant materials soaks for approximately 48 hours, and a dramatic color change to bright neon green is noted in the soaking water, an alkaline substance is added until the soaking liquid reverts to a brownish color, and the liquid is then paddled to introduce oxygen through agitation. As oxygen is introduced, the indoxyl is converted to insoluble indigotin (blue indigo pigment), which settles along with the lime substrate to the bottom of the vat, where it can then be collected and stored.
Two 300-gallon livestock water tanks were used to hold the water and dyeplant materials as they soaked. An in-depth demonstration of this process is available on the indigo-processing video created through this project. Batch 1 and 2 were harvested and weighed, then entered in the tank and allowed to soak for two days. Aquarium heaters and plastic tarp covers were used to help maintain the temperature of the soaking tanks overnight. We attempted to standardize the temperature of the soaking liquid using 3-4 aquarium heaters per tank, although we admittedly had a difficult time keep consistent temperature between the trials during the variable fall weather. Leaving the tanks in a heated or even unheated greenhouse would have been preferable to hold the temperature more constant. When the soaking liquid became neon green, up to two days later, the soaked plant material was removed and discarded. Calcium hydroxide (pickling lime) was added until the soaking liquid's color shifted to brown. Then paddles and garden hoes were used to agitated the liquid and introduce oxygen. This agitation continued for approximately twenty minutes, until blue pigment began to visibly precipitate from the liquid. We allowed this pigment to settle overnight, then decanted the clear liquid on the top and placed the settled pigment-sludge into storage containers. The 300 gallon tanks were then cleaned and refilled with water, and the same process was repeated with Batch 3 and Batch 4.

The following table compares the processing variables among batches. In addition to the differences in harvested dye materials, there was wide variation in the amount of calcium hydroxide added from one batch to the next, since the amount to be added was determined by a visual analysis of the color change in the soaking liquid (from green to brown or brown-purple in the case of Batch 4) and not a set amount such as percentage of weight of plant material. There was also variation in the average temperature of the soaking liquid. These factors, the quantity of lime added as well as the average temperature of soaking, likely impacted the quantity and quality of dye produced by each batch. The last column gives an approximation of how many grams of “pigment-sludge” were produced from each batch. Ultimately there was great variability in the amount of pigment produced between batches. We presume this variability most likely has more to do with variation in the quantity of materials and processes affecting yield, rather than differences in pigment concentration within the fresh indigo plant at time of harvest.

See Table 1: Harvest Weight, Pigment Extraction Variables, and Estimated Pigment Yield

Since the pigment-sludge we produced appeared to have a high liquid content, we performed tests to determine the approximate percentage of solid material. Three separate samples from each batch were weighed, then dehydrated. Average masses pre- and post-dehydration were calculated and used to assess the approximate percentage of solid material; results are recorded in the table below. Indigo powder is ultimately sold by dry powder weight. Additionally, three separate samples for pigment processed during a separate experimental project at a farm in Edmonton, Kentucky were assessed and are included in the data in the table below.

See Table 2: Pre- and post-dehydration masses

Conditions for indigotin testing

Once we had produced our storable pigment-sludge, we had to develop a low-cost method for assessing the relative concentration of indigotin of each batch of sludge. We chose to establish indigotin concentration by using sludge from each batch to set up test vats, dyeing a test fabric strip in each vat, and doing a visual comparison of relative dye intensity on the fabric.
Indigotin, the active blue pigment extracted from the dye plants, is insoluble in water. In order to dye the indigotin must be reduced in an alkaline solution. Under alkaline conditions the indigotin gives up one oxygen molecule and converts to “indigo white”. Fibers or fabric added to this dye vat are able to absorb the soluble “indigo white”. Then, when removed from the dye vat and exposed to air, the “indigo white” reoxidizes, returning to its blue, insoluble state, and remaining fixed on the fiber. A dye vat is typically set up by adding indigo pigment to a vat of alkaline liquid, then reducing the solution chemically or through a fermentation process.

Our test vats were set up using indigo sludge (or powder), soda ash (an alkalizing agent), thiourea dioxide (a chemical reducing agent) and water. A control vat was set up using a high quality purchased ground indigo obtained from a wholesale supplier. This vat was set up using 3 grams purchased indigo, 21 grams of soda ash, 1.5 grams thiourea dioxide, and one quart water. Soda ash was dissolved into the water and stirred for two minutes. Purchased indigo was then added and the solution was stirred for an additional two minutes. The thiourea dioxide then added, the solution was stirred for another minute, then capped and set to the side to allow reduction.
Vats were set up for each of the experimental conditions using the ratio of nine parts indigo sludge, three parts soda ash, one part thiourea dioxide, and one quart water, prepared in the same manner as the control vat.
Once the vats had fully reduced (as evidenced by the interior vat liquid color becoming uniformly amber green and the surface of the vat producing a coppery scum), we entered cotton jersey fabric into each vat. A series of three dips was made, with each dip lasting for two minutes. After each dip, a small swatch was cut off, washed, dried and labeled. The swatches were then compared visually to estimate the relative concentration of each experimental vat, and a series of calculations was performed to assess the approximate indigotin content.
While Batch 1 and Batch 3 yielded excellent quality blue pigmentation on the fabric samples, neither Batch 2 nor Batch 4 yielded appreciable results. Batch 2 resulted in very pale powder blue on fabric even after multiple dips. Batch 4 resulted in a pale purple on fabric. We believe that this may be due to our growing, harvesting and / or pigment extraction methods somehow extracting greater concentrations of indigorubin, a purple-red pigment also present in Persicaria, also known as indigo-red or inidigo-purprin. However, we are uncertain which variables in any stage of our growing, harvesting and pigment extraction resulted in the increased indigorubin content. Batch 4 was the most heavily browsed by cattle during the electric fencing failure. We hypothocize the stress conditions n late summer caused the greater development of the red pigments in this test plot. While to goal of our research was to find a method for producing quality blue, it is worth exploring whether there is a separate market or higher value for the red-indigo.

For the purposes of our calculations we assessed the approximate indigotin content of only batches that yielded measurable indigo color on fabric. Batch 1, Batch 3, and the batch of pigment processed during the separate experimental project at Hill and Hollow Farm in Edmonton, Kentucky. Based on our calculations, we determined that our indigotin yields were between 1% and 3.5% of the plant material harvests. These figures are roughly in correspondence with historical levels of indigotin in locally-processed indigo in the 18th and 19th century, according to sources such as Jenny Balfour-Paul in her reference book Indigo.

Under these experimental conditions, less than 1% of the weight of fresh harvested plant material wound up as usable blue indigo pigment. With attention to processing variables, as well as exploration of alternate and more consistent processing methods, the indigotin content in the finished processed material could likely be made much higher. Additionally, refining harvesting and pigment extraction procedures would likely help avoid situations like we encountered in which both Batch 2 and Batch 4 did not yield appreciable amounts of blue pigment. As will be discussed in the Future Recommendations Section, the open questions remain: how do we make the pigment extraction process more efficient, replicable, and high yield? And how do we reduce variability across batches of raw plant material?

See Table 1: Approximate Indigotin Content
See Table 2: Estimated pigment yields

2011 P. tinctoria research outcomes

Since our grant year was extended to provide time for the germination trial, we decided to include data gathered on the yields of P.tinctoria in a plot grown under drip irrigation conditions during 2011. While not a part of the official SARE study, we think they can inform other growers on deciding to grow this crop. The 110 foot row was double planted (staggered) with P. tinctoria with approximately 18-24 inch spacing on a 36” bed. The double harvest yielded approximately 240 lbs of fresh leaf material (including stems as the above data sets), or 109,200g. Therefore we could expect that a single row would yield 54,600 g (120lbs) at least. This plot received relatively consistent irrigation and was fertilized with fish emulsion twice in early season. We did not use precipitation method to extract the indigotin from this harvest, choosing instead to field dry (on tarps) and thresh it for composting method.

Outreach Outcomes

The ultimate goal of our outreach was to see if there was sufficient interest to create a grower cooperative. Such a cooperative would hopefully lower barriers to profitable dyeplant growing and provide resources for obtaining dye seeds, sharing processing equipment and methods, and ultimately, gaining sufficient market access. We also sought to increase public awareness of natural dyeing and regional dye sourcing options for fashion designers and fabric dyers/craftspeople. So, in addition to getting preliminary growing data on growing and processing indigo varieties in Tennessee, in 2010 we did several outreach events to share our experience growing indigo. We hosted a 2 day workshop during our indigo harvest period in October 2010 in which 20 people came to the farm to learn more about growing and harvesting indigo. This took place over a full Saturday and Sunday, with participants coming from as far as Pennsylvania. Most participants were from within a 50 mile radius of Nashville. We also had an information booth at the Southern Sustainable Agriculture Working Group (SSAWG) conference in Chattanooga, TN during January 2011, allowing us to interact with more growers and extension personnel and do more outreach on the growing of natural dyes in general and indigo in particular. While we were not able to share final research project results at the SSAWG conference, we collected names and contact information for those interested in learning more about the project and potentially growing natural dye crops on their farms. A major portion of our project was creating an 8 minute instructional video on growing and processing indigo, which is now available for free on the internet. Scenes from the 2011 indigo growing plot were also filmed by a movie producer to be included in a documentary about eco-fashion.

Indigofera tinctoria seed germination

In 2011 we did a small study to figure out a way to get more consistent germination with the Indigofera seeds, which have a very hard seed coat.

In our first run of this trial, we had pretty poor germination results across the board. We made 56 cell trays each with 6 different variables. Results were as follows after 5 weeks (March 17-April 27):
Control: 1 germinated or 1.8%
S0 (no soaking, scarification and but sat in light for 3 days before planting): 6 or 10.7%
S1 (scarification and soak in hot water turning to room temp for 1 day): 1 or 1.8%
N1 (no scarification and soak in hot h20 turning to room temp for 1 day): 1 or 1.8%
N3 (no scarification and soak 3 days): 1 or 1.8%
S3 (scarification and soak 3 days): 1 or 1.8%
This test was done in a heated room under florescent light kept at average 70 degrees. We decided to do another trail. This was in the same heated room but with different variables somewhat.

We found that within 10 days (May 2 to May 12), results were as follows:
Scarify with file and nick with knife, plant immediately: 6 out of 18 cells or 33%
Scarify with file and plant immediately: 8 out of 36 cells or 22.2% germination
Scarify with file and let sit 4 days before planting exposed to light no water: 10 out of 60 cells or 16% germination
Control: no scarification or nicking: 0 out of 12 or 0%

In future tests it would be good to determine an easier way to nick the seeds, perhaps with a nail clipper. This would be a labor intensive thing to do by hand if you were drilling the seed over a larger acreage.

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

A major part of our project was producing an instructional video for growing and processing indigo. We had originally set out to do 3 2-3 minute videos but instead produced one 8 minute video which provides an overview of the Indigo containing crops, growing conditions, and focuses most on the technicalities of processing indigo into pigment using the precipitation method.

Project Outcomes

Project outcomes:

Performing this study has already made an immediate impact on the indigo growing on at least one Middle Tennessee farm. By hosting farmers and artisans at our field days, we have also increased public awareness about the possibility of raising natural dye crops, especially indigo. With this initial interest, we have organized three Tennessee farms together to form a steering committee to explore the potential of establishing a collective of dye growers. Tentatively called the Local Color Collective, member farmers are seeking to launch a business that processes and markets natural dye materials that have been cultivated on the member’s farms in Tennessee, as well as potentially including other neighboring states as the membership expands. This group of farmers has received a VAPG planning grant to do a feasibility study to determine the market potential and answer some of the logistics questions related to processing four potential natural dye crops. We have also developed a relationship with the Small Farms Unit at Tennessee State University which we hope to continue to get more research support in this field, whether in the private or public sector.


Potential Contributions

We believe this project will spark greater interest among farmers in growing natural dyeplants in general and indigo in particular. Based on interest in our field day/workshop and local press such as an article in the Nashville Lifestyles magazine, we also believe we have shown that this is an exciting field to many people in the general public and that more research is needed in this area so that farmers can figure out the best way to capitalize on this interest. Perhaps an added value to famers beyond the farm gate crop prices could come through organizing an agritourism effort around natural dyes, similar to a quilt trail. Over the past two years we have experienced an increased interest among artists, craftspeople and designers in utilizing locally grown dyes. We have also had farmers (besides the three that are organizing the Local Color Collective) express interest in natural dyes cultivation.
We expect our 8 minute instructional video on growing and processing indigo plants to fill a void in information available to growers seeking to process their own dye plants into storable dye material. The producers in this grant had to learn through trial and error the best way to grow and process the dyes, with limited public information. We hope by synthesizing the information in a free video describing and documenting the processing via precipitation method in step-by-step form, we will make it easier for growers to adopt this new crop and potentially process it themselves. We also hope the video will interest some researchers or extension personnel to help us determine more effective and efficient processing techniques.

Future Recommendations

Running this research project has greatly improved our knowledge of indigo crops and we look forward to continuing to grow indigo. We plan to keep compiling the information we learn into something that other producers can utilize. We have found a lot of individual and press interest in the project, leading us to believe that natural dye extracts or naturally dyed goods can be a valuable niche / value added product for Southeastern farms. We also realized that there is much more research that needs to be done before farmers can have all the information they need to decided whether to grow dye crops and what the best way of growing and processing these crops is. Our forthcoming feasibility study will assess the market capacity and best opportunities for growing natural dyes, in addition to tackling the value-added dye extract processing questions. General crop production questions are still looming for the three types of indigo but the processing question seems to stand out as the greatest need. It is clear from this research that indigo-containing crops can be grown in Middle Tennessee. But, there are still many outstanding questions including but not limited to production, processing, and end market for dyes and pigments (or dyed goods).

Part of the goal of this SARE grant was to lay the groundwork to create a Southern natural dye growers' network that will at minimum share best practices in the cultivation and processing of plant-based indigo and other natural dyes. According to Charles Martin, Agriculture Specialist at New Mexico State University, and lead researcher on a 2006-2007 WSARE grant Growing and Marketing Dye Plants as Alternative Crops, in the Southwest US, “in order to meet the wide range of colors and plant materials, [researchers] recommended in the report that growers form a co-op or coordinate their production to be able to provide a wide range of colors, and not create a glut of a single crop.” So, while research on indigo-containing plants must continue, we will also need more formal research on the other popular dye crops utilized in commercial dyeing. Luckily, there appears to be already published research on the best agricultural practices for at least a few of these crops.

Initially, it is assumed that a grower’s network could be launched with four key raw materials: indigo (blue), madder (red), marigold (yellow), and weld (yellow), which have been successfully cultivated in Tennessee for several years. It is assumed that the plant materials will be processed using technology that is scalable for small scale processing to turn the plants into dye extracts. Ultimately, the natural dye extracts may be sold into the specialty textile industry, either domestically or abroad, for example denim dyeing with natural indigo. Other outlets for dyed products, such as natural food colorant or cosmetics and natural hair colorants, may eventually be explored to diversify the revenue stream for the Local Color Collective if there is sufficient value-added product.

Currently, the test plots and processing techniques used by the steering committee farms are likely too small and the current processing both too labor intensive and not efficient enough to have enough high quality dye to build a strong brand and bring the product to market. Our experience and the global branded examples highlighted in the introduction show that our goals are technologically feasible but we must find out how to scale up and refine our existing production and processing practices to make a high quality extract. We have general knowledge of how on a small scale to process raw natural dye material but do not yet have standards developed or know what specific equipment and environment is necessary to create value added dye extracts of consistent and high quality. Thus, we hope more formal public research will be done in the Southeast region on this topic.

More investigation into the technical feasibility of growing and processing dyeplants, including indigo, is still needed to make these crops profitably adopted by growers. In addition to needing more research on the physiolocal and agronomic factors affecting the quality and yield of the indigos, we are interested in the ability to improve quality and yield by selection, breeding and production practices. We are not aware of how much recent plant breeding has been invested in recent years in indigo plants, as their commercial potential was highest in the 1800s before modern breeding techniques.

Finally, one of the most surprising parts of the study for us was the massive variability in the final pigment yield, with two out of the four text plots yielding no appreciable pigment. We believe this was not related to the growing condition but rather the processing variables. It will be critical for more research on the best conditions for (and economics of) processing plant materials into dyes to make sure that plant harvests are actually able to be turned into pigment. How dye quality rather than quantity is achieved is an outstanding question.

Once there is a standardized means of processing the plant matter into pigment, information regarding the relative economics of dye/pigment yield per acre of natural plant materials can be better extrapolated, as well as estimated profit per acre and margins over other value-added products. This will be the ultimate question in farmer adoption and unfortunately one we do not have a definitive answer for yet. There will be other logistical questions such as the storage and distribution requirements of the processed extracts.

While we assume a market beyond textiles is possible, we are not yet experienced in this area. There is a growing and robust natural colorants market for food products, especially since the European Union recently banned the use of any synthetic colorants in food products. The lack of a quality blue pigment, for example, lead to products being removed from the grocery shelf, and prices of other natural dyes, such as cochineal (red) have increased up to 3 fold over their 2008 value. It is clear that there are many more emerging and existing markets beyond textiles for these natural colorants created from natural dye extracts.

In short, industries from food to textiles will continue to look for non-toxic alternatives to synthetic dyes and pigments. Sustainably-grown natural dyes from Southeastern farmers have a tremendous growth opportunity to expand into a number of industries and products. The natural colorant market in the food industry has grown at a time when the rest of the food colorant (synthetic) industry has stagnated. The market for organic cotton and fabrics produced with environmentally friendly attributes has grown and more manufactures are considering the processes which are used to scour, dye, and fix their fabrics. Outside of industrial uses, the home artisan and craft markets has had a surge in interest, with an increasing numbers of people taking up knitting, sewing and other fiber arts. We believe this market alone could support a small cooperative of farmers raising natural dye crops and based on our workshop interest, there appears to be widespread interest among artisans to learn more about the use of natural dyes.

Before widespread farmer adoption, this topic will need more research on cultivation requirements, processing requirements, and market potential and access. We plan to do a feasibility study and business plan before recruiting new farmers into our grower’s network.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.