To get the blue pigment from woad, it is important to use leaves from the plant's first summer. Harvest the leaves in late July and August, preferably during a warm spell. Leaves need to be fresh and should be used as soon as possible after harvesting as the pigment can deteriorate rapidly.

How do you harvest woad for dyeing?

There are two ways you can go about picking the leaves during a first season woad dye harvest. You can either remove the entire rosette, leaving just the roots intact, or you can pick only the largest leaves, the ones that are 6 inches (15 cm.) or longer, and leave the shorter leaves in the middle of the rosette.

How do you process woad?

Woad plants are ready for harvest in the summer months. Take the leaves from the base of the plant and then cut them into small pieces. Submerge the torn or cut leaves in a stainless steel pan of water and bring up to a temperature of 175F (80C). Simmer for about 10 minutes.