Feature of Japanese greenalder

A deciduous small tree commonly found in Honshu, Shikoku, and Kyushu. In early spring, around March to April, it produces numerous yellow, filamentous flowers. As autumn deepens, cone-like fruits that form at the tips of branches are collected and utilized for dyeing. Owing to their antimicrobial properties, decoctions made from the dried cones have traditionally been used to wash affected areas of burns and frostbite, serving as a remedy to reduce skin inflammation. The leaves have also been employed in traditional black dye preparations such as ohaguro (a historical practice of tooth blackening).
In recent years, this species has been utilized for erosion control and slope greening, due to its ability to thrive in nutrient-poor soils. Additionally, it has been applied in aquarium water treatment, where tannins—organic acids contained in the plant—contribute to acidifying the water and improving its quality.

As the cones dry, they undergo a chromatic transformation, turning brown. These desiccated cones can be harvested and stored for future use.

Fresh cones harvested around August may also be dried and stored for later use. Since they still contain the enclosed nutlets (achenes), they tend to yield a deeper and more intense coloration during the dyeing process.

About Japanese greenalder dye

Although this plant has been utilized as a dye source since ancient times, it came into particular prominence during the Edo period, when it began to be used as a substitute for gobōshi (gallnuts) in black dyeing. In contrast to the purplish-black hue produced by gallnut-based dyes, this dye yields a greenish-black tone.
The dyeing material can be obtained either by harvesting and drying the immature, blue-hued cones prior to autumn, or by storing the already matured, cone-like dried infructescences, allowing for year-round dyeing. While the branches and leaves are also usable for dyeing, their lower tannin content results in yellow or brown shades rather than black.
Several species are used for this purpose, including Alnus sieboldiana (Ōba-yashabushi), Alnus pendula (Hime-yashabushi), and Alnus firma var. hirtella (Miyama-yashabushi), although there is no significant chromatic variation among them in terms of the dyed result.
A historically significant example of this dyeing technique is the color known as Mito Black (Mito-guro), which was favored by Tokugawa Mitsukuni, the second lord of the Mito Domain. This deep black was achieved through a meticulous process in which indigo dyeing was used as an underlayer, followed by multiple applications of dye extracted from Yashabushi (alder cones), resulting in a profound and lustrous black.

Method of dyeing

The dyeing process employs a mordanting technique. Dried cones are placed in a stainless steel pot with water, brought to a boil, and decocted over heat. After approximately 30 minutes of extraction, the liquid is filtered through cloth to obtain the dye liquor, which serves as the primary dye solution. Up to four or five successive extractions can be performed from the same plant material.
Due to the high tannin content of the cones, the dye exhibits excellent substantivity, particularly on cellulosic fibers, eliminating the need for a proteinaceous pre-mordant such as gojiru (soybean milk), which is typically required in plant dyeing to improve fixation.
Repeated cycles of dyeing and post-mordanting—especially with iron (ferrous sulfate)—result in progressively deeper shades, ultimately producing a near-black color. Different mordants yield a spectrum of hues: aluminum (alum) produces beige; copper (copper sulfate) yields light brown; titanium results in an apricot-like tone; and iron mordant produces a deep black.

Color deference by mordant