In spring 2014, with the kindness of a neighbour who let us use part of a field, we began the Hitotsuya（ひとつ屋） Dye Plant Farm.
As the name suggests, we mainly grow plants used for natural dyeing.
The crop we cultivate every year as our main dye plant is Japanese indigo, known in Japan as tade-ai.
This article introduces the method we have actually used at Hitotsuya, following the seasons from preparing the field and sowing seed to raising seedlings, transplanting, feeding the plants and harvesting them.
Tokushima Prefecture, the traditional home of Awa indigo, introduces the process from sowing in a seedbed and transplanting to the first and second cuts and the preparation of dried indigo leaves on its official About indigo page.
Growth varies with climate and soil, so the method described here is a record of what Hitotsuya has developed through repeated cultivation in its own field.
The work from sowing to harvest can also be seen in our YouTube video How to grow Japanese indigo.
Around the beginning of spring | Weed the field while it is still winter
At Hitotsuya, fieldwork begins each year when the daffodils flower.
Their clean, delicate flowers again announced that it was time to begin working the soil.
▼ Daffodils marking the beginning of fieldwork
In mid-February, the field still looks dormant. Only a few small weeds have begun to emerge.
Removing these young weeds and the dead roots of old plants before spring arrives makes the later work much easier.
▼ Weeds beginning to appear in the winter field
Around the spring equinox | Cultivate the soil and sow the indigo seed
As the cold eases and the sunlight softens around the spring equinox, work in the field suddenly becomes busy.
We once again remove weeds and dead roots, then cultivate the soil.
▼ Weeding and cultivating the field around the spring equinox
At Hitotsuya, we use 21 March as our usual guide for sowing Japanese indigo.
The suitable date varies with the region and the temperatures that year. If strong cold continues, sowing should be adjusted until the seedlings can be managed safely after germination.
That year, we grew two types sent from Tokushima, the home of Awa indigo: Senbon-ai and Chijimi-ai. It was our first year growing Chijimi-ai.
▼ Seeds of Senbon-ai and Chijimi-ai ready for sowing
Sow in rows in a seed tray
Rather than sowing directly in the field, we first sow the seed in shallow rows in a seed tray.
Make shallow furrows in the soil, scatter the seed and cover it with only enough soil to hide it.
The sowing process is also introduced in our Japanese-language article Sowing indigo seeds—and what is taisei?.
▼ Japanese indigo seed sown in rows in a seed tray
Keep the seed warm and moist until germination
After sowing, cover the seed tray with plastic to retain warmth and moisture. The cover also helps prevent birds from eating the seed.
At Hitotsuya, we place the entire tray inside a large transparent bag so that insects and slugs are less likely to enter.
We have previously lost newly germinated seedlings to slugs. Extra care is needed in damp places.
▼ Seed tray covered with plastic for warmth
After germination, provide sunlight and do not let the soil dry out
When temperature and moisture conditions are suitable, tiny shoots appear in about a week.
Once they have germinated, remove the plastic and grow the seedlings in the spring sunshine.
The most important point during this stage is not to let the soil dry out.
A strong stream of water can wash away the tiny seedlings and the soil around them. Fit a rose to the watering can and water gently every day.
▼ Newly germinated Japanese indigo seedlings
Around Grain Rain | The seedlings grow rapidly
After another two or three weeks, the seedlings grow quickly and reach about 10 cm in height.
As the plants become larger, their leaves lose more water through transpiration and the seed tray dries more quickly. Check the moisture below the surface as well as on top.
▼ Chijimi-ai seedlings about 10 cm tall
By Japan’s Golden Week holiday period, the seedlings are usually about 15–20 cm tall.
The tray becomes crowded and the leaves overlap. The time for transplanting to the field is approaching.
▼ Crowded Japanese indigo seedlings before transplanting
This is Senbon-ai, the type we had mainly grown at Hitotsuya. At this stage its leaves resemble basil.
This is Chijimi-ai. As its name suggests, the leaf surface has a crinkled appearance.
Because its flowering time and growth pattern differ from those of Senbon-ai, the two should be observed separately when seed is to be saved.
Around the beginning of summer | Prepare the field before transplanting
When the seedlings are large enough, it is time to transplant them to the field.
At Hitotsuya, we cultivate the field about a week beforehand and incorporate dolomitic lime, compost and rapeseed oil cake into the soil.
This feeding method suits the condition of our own field. The materials and quantities needed will vary according to the soil and the fertiliser applied in previous years.
▼ Field cultivated and fertilised before transplanting Japanese indigo
Remove the seedlings from the tray
Lift the seedlings from the tray and separate them carefully so that the roots are not damaged.
At Hitotsuya, we lightly rinse away the attached soil with water so that the condition of the roots can be checked.
▼ Japanese indigo seedlings removed from the tray and their roots prepared
Plant five or six seedlings together, vertically and deeply
Dig holes about 10 cm deep and plant the seedlings in groups of five or six.
Shallow planting leaves the young plants vulnerable to wind and rain. We plant boldly and deeply, burying the lower part of the stems.
As Japanese indigo grows, roots can also develop from the stem nodes and the plant spreads close to the ground. Some growers make use of this habit by laying the seedlings diagonally.
At Hitotsuya, however, we do not lay them down. We have continued to plant them straight down and deeply in a vertical position.
We first chose this method because our field was small, but for more than ten years it has allowed us to grow and harvest Japanese indigo without major problems.
▼ Several seedlings planted together, vertically and deeply
Leave about 40 cm between planting groups
We use approximately 40 cm as the guide for spacing between groups.
Because our field is limited in size, the groups are staggered so that as many plants as possible can be fitted into the available area.
▼ Senbon-ai planted in a staggered pattern at about 40 cm spacing
We planted Chijimi-ai in a different field to reduce the possibility of crossing with Senbon-ai.
When seed is to be collected for growing the same line the following year, each type should be managed in a separate area.
▼ Chijimi-ai planted in a separate field for seed saving
Around the summer solstice | Feed and earth up the plants
When the rainy season begins in June, Japanese indigo grows very rapidly.
If the stems lengthen and the plants begin to lean, place rapeseed oil cake or another suitable fertiliser around the base and earth up the soil.
We do not make high ridges at transplanting because soil is added around the plants as they grow, gradually forming a ridge later.
▼ Japanese indigo growing in the rain of the early summer season
By late June, the branches and leaves overlap and the crop becomes very dense.
Air circulation is reduced inside the plants, so we check for insects and damaged leaves while waiting for the harvest stage.
▼ Dense Japanese indigo covering the field in late June
Around the beginning of midsummer | Harvest the first cut
Traditionally, the first Japanese indigo harvest is said to take place after Hangesho, a seasonal marker in the old Japanese calendar.
Hangesho falls around the eleventh day after the summer solstice, generally in early July. In 2020 it fell on 1 July.
When the leaves are fully developed and before flower buds become prominent, we harvest the first cut of indigo.
▼ Field ready for the first Japanese indigo harvest
Cut while leaving the base of the plant
Cut the stems with a sickle or garden shears, leaving about 10 cm above the ground.
Leave the parts around the base from which new shoots can emerge, then feed the plants after cutting so that branches and leaves can regrow.
Depending on temperature and rainfall, the plants may be ready to harvest again after about a month. This is the second cut.
If the plants remain vigorous, continued feeding and care may even allow a third cut. Leaf quantity and quality change with each harvest, so the plants must be assessed every time.
To obtain seed reliably for the following year, decide in advance which plants will be left uncut for seed and allow them to flower and set seed.
▼ First-cut Japanese indigo harvested about 10 cm above ground
Turn the harvested indigo into dye material
Freshly harvested Japanese indigo can be used in several ways.
The fresh leaves can be used for fresh-leaf dyeing, dried leaves can be prepared for making sukumo, and the crop can also be processed into precipitated indigo paste.
▼ Freshly harvested Japanese indigo
When the leaves are dried thoroughly, they become dried indigo leaves that can be stored for a long time.
Dried indigo leaves do not produce an indigo blue simply by being boiled like an ordinary plant dye. They require a dyeing method suited to their condition or further processing into sukumo.
The drying process is explained in our Japanese-language article Lye-fermented indigo vat ① | Sun-drying indigo leaves in preparation for making sukumo.
▼ Dried leaves for sukumo and dried-leaf dyeing
The harvested leaves can also be soaked in water to extract their components, then mixed with lime and agitated so that the blue material settles as precipitated indigo.
Our method is described in the Japanese-language article How to make precipitated indigo, indigo paste and dried indigo cakes.
▼ Precipitated indigo paste made from Japanese indigo
The Japanese indigo method developed at Hitotsuya
The method described here is not the single correct method for every region and growing condition.
Growth changes with soil, climate, rainfall, sunlight, feeding, watering and insect pressure.
At Hitotsuya, however, we have harvested Japanese indigo every year by continuing to sow in rows in seed trays, transplant five or six seedlings together, leave about 40 cm between groups, plant vertically and deeply, and feed the plants after cutting so that they regrow.
Rather than deciding everything in advance, observe leaf colour, stem thickness, the way the soil dries, insects and the speed of regrowth, then find a method suited to your own field.
Sowing the seed, raising the plants and receiving colour from the crop you have harvested yourself turns indigo dyeing into a year-round practice, not merely the act of placing cloth in a dye vat.