Black Walnut (Juglans Nigra): is also known as American Walnut. Walnuts have been recognized as one of the oldest tree foods known to man, dating back to about 7000 B.C.. The black walnut is a hardwood tree that frequently grows to a height of one hundred feet with a trunk diameter of up to six feet. It grows in much of North America as well as Europe. Black walnut drupes contain juglone (5-hydroxy-1,4-naphthoquinone) plumbagin (yellow quinone pigments), and tanin. The brownish-black dye was used by early settlers to dye hair. Extracts of the outer soft part of the drupe are used as a natural dye for and the tannins present in walnuts act as a mordant aiding in the dyeing process and are usable as a dark ink or wood stain.