The wood is a light reddish brown with a coarse texture. Matures at about 60 years, the leaves have a distinctive serrated shape and are fairly broad.
From the time of Theophrastus the bark of the young shoots has been used for dyeing and tanning leather. When these shoots are less than a third of an inch in diameter their bark yields no less than sixteen per cent. of tannin. They produce red, brown, or yellow dyes if used alone, and black on the addition of copperas. The natives of Lapland are stated to use the Alder as a dye for their leather garments.
"They scraped it off (the alder bark) in very fine pieces and rubbed it directly on the skin to be dyed. The dryer the skin the quicker it took the dye. Some skins required two or three applications. Then the sides were folded against each other and the skin was left in a cool place overnight. Shaken free of bark in the morning, it was rubbed and pulled with the hands in all directions. Worked, allowed to dry, worked etc., until it was dry and soft. Oil might be applied if the skin were too hard."
Some images of a young Alder;
In Mors Kochanski's book Bushcraft, he also mentions the high tannin content in the twigs for use as an astringent. An astringent causes tissue to become more compact, such as in the contraction of muscle fiber, blood vessels, or the coagulation of protoplasm of the surface cells, thus diminishing either discharge or bleeding from an external or internal body surface. In the case of a wound or sore, discharge is reduced or stopped, tissue tone improved and healing quickened if the water in which alder bark has been boiled us used as a wash. A moist poultice of the inner bark can be applied to wounds that bleed profusely. This is of particular importance to those of us using sharp tools in the back country.