Dyers woad (Isatis tinctoria) grows as a winter annual, biennial or short-lived perennial and ranges in size from one to four feet tall. It produces a basal rosette of leaves during the first year and a single stem that bears yellow flowers the second year. The leaves are blueish-green and range from one to seven inches in length. The small yellow flowers are found in terminal clusters on the branch tips. The fruit is a flattened seed pod that hangs from a small stalk. Initially the pod is hairless and green, but it matures to a black or dark purplish brown. The seed pod is a distinguishing characteristic, and it is used for plant identification after flowering. Each pod produces just one seed. The seeds are brownish yellow and cylinder shaped.