An upright biennial, or sometimes a short-lived perennial, up to 1.2m high, with basal rosettes of oblanceolate leaves, stems with arrow-shaped leaves, and heads of yellow flowers in early summer, followed by brown seedheads in late summer. The flowers are good for bees, and the famous blue dye is obtained from the leaves. The highest concentration of indigo is in the first-year leaves, harvested in late summer.

Dye colour: Blue, Yellow

Dye source: Leaves, Flowers

Flowering: May - July

Other common names: Ash of Jerusalem, Common dyer's weed, Dyer's weed, Dyer's woad, Jerusalem ash

How to extract the dyes: 

• Soak the dried flower heads in a pot filled with 4 litres of warm water for 30 minutes. 

• Heat the dye bath to +70 °C, well below the boiling point.  

• Adding one tablespoon of washing soda or 0.5-1 dl of wood ash lye can improve the colour extraction and modify the colour from brown to orange. 

• Steep the flowers for 30 minutes to extract dye.  

For more information about the dyeing process:

Natural dyes for education and colour experimentation