Dyer's woad, isatis tinctoria, is a biennial or short-lived perennial native to Europe. Woad is prized for the chemical indigotine found in its leaves. Indigotine is used to create the color indigo. While herbalist value woad in the garden, it is considered a noxious weed in the Western United States. Dyer's woad is found in the wild in disturbed or cultivated fields and along roadsides. Always remove faded flowers to prevent dyer's woad from releasing its seeds. One plant can produce 10,000 seeds that can lay dormant in soils for years before sprouting.
Remove any faded flowers before seeds form. Once dyer's woad produces seeds, the plant will die.
Cut leaf stalks back to the crown (the junction between roots and leaves). Leave the rosette of leaves that constitute the crown intact.
Cover dyer's woad after the first hard frost with two to three inches of fluffed straw.
Remove the straw covering in early spring or when you see signs of growth from the crown of the dyer's woad.