At the Hitotsuya（ひとつ屋） dye garden, we grow a range of plants and use them to make our own natural dyes. It is only a very small plot, but the largest area is devoted to Japanese indigo (Persicaria tinctoria).
This year, too, we sowed the seed around the spring equinox and transplanted the young plants into the field in May. The transplanting work is recorded in our Japanese-language article Transplanting Japanese indigo.
By summer, the plants had grown this large.
▼ Japanese indigo grown tall by summer
A delayed first harvest
We had originally planned to harvest the crop in early July. A knee injury prevented the work, however, and only recently were we able to cut part of the field.
In a normal year, the season’s first harvest—known in Japanese as ichiban-ai—is used to make indigo paste or precipitated indigo.
Making precipitated indigo is unexpectedly demanding physical work. As the knee had not fully recovered, we decided not to force the process and instead dried the harvested leaves for storage.
The method for making precipitated indigo from Japanese indigo is explained in our Japanese-language article How to make precipitated indigo, indigo paste and dried indigo cakes.
Removing the leaves and drying them in the sun
After harvesting, each leaf was removed from the stem and spread out in the sun.
The drying itself was straightforward, but removing the leaves one by one took considerable time, especially when handling a larger harvest.
▼ Indigo leaves just removed from the stems
Green leaves turn a deep indigo colour
The leaves were green when first laid out, but after about two days of drying they had lost much of their moisture and taken on a visibly deeper indigo colour.
▼ Dried indigo leaves after the colour change
Dried indigo leaves cannot simply be boiled for blue dye
Once thoroughly dried, the leaves can be stored for a long period. They cannot, however, produce an indigo blue merely by being simmered like an ordinary plant dye.
The compounds and enzymes remaining in the leaves vary with the drying method, so the dyeing process must be chosen accordingly. A Japanese-language paper published in the Journal of Home Economics of Japan, Preserving indigo leaves while retaining indican and using them for dyeing, examines the relationship between leaf preservation and later dyeing.
Once the knee has recovered a little more, we plan to use these stored leaves and introduce the dyeing method in a future article.