As early as prehistoric times, woad (also known as dyer’s rocket) was spread around Europe as a dyeing plant. One of the areas where the plant was cultivated was the area around the East Flemish town of Aalst. Woad contains the coloring agents luteolin and apigenin, which make it suitable for yellow dye. The greatest concentrations are found in the tops of the shoots and in the seeds. For dyeing, the woad was first boiled in water with urine to promote the release of the dyes. When dying textiles, alum and bran were used as mordants.