Isatis tinctoria

Germination

Sow directly in spring. Surface sow onto prepared soil which has been raked to a fine tilth. Sow in rows. Rake the seeds into the soil. Germination will occur when the soil reaches 10-13°C. and danger of frost has passed. Germination takes 1-2 weeks approx. Water well. Thin seedlings to 30cm spacing.

Growing

Prefers a well-drained alkaline soil in full or partial sun. Will tolerate any soil. If your soil is not alkaline add some lime to it a few weeks before planting out the seedlings. As this plant is a member of the Brassica family do not plant where other Brassicas have recently grown to prevent club root. Hardy to -15°C.

Cultivation

Will self-seed freely, as you do not want to have this plant in the same spot for 2 consecutive years (club root can be a problem) cut back flower stalks leaving just 1 or 2 where the seed can be collected from and sown elsewhere next year. To harvest the leaves for dye making cut leaves with secateurs. Wash in a bucket of water, tear leaves. place in a large pan with rain water, heat to 90°C but do not boil. Steep for 10 mins in the hot water. Then plunge the pan into ice of cold water to cool it down quickly, stir and strain, squeeze the leaves to extract all dye. The leaves can be composted. Add soda ash to the water when it is cool. Aerate the solution for 10 mins with a whisk. Allow pigment to settle for 2-3 hours, remove excess liquid and filter the remaining pigment.