Erect biennial , sometimes winter annual or short-lived perennial, to 1.2 m tall. Immature plants exist as basal rosettes until flowering stems develop at maturity. Plants are highly competitive and often grow in dense colonies . It was cultivated for several centuries in Europe as a medicinal herb and source of blue dye.
Foliage contains compounds that appear to have insecticidal and fungicidal properties.
Subsequent few leaves resemble first leaves. Flowering stems typically several per rosette, gray to purplish, glabrous, typically branched near the top. Midveins conspicuously pale . Taproots of rosette and mature plants penetrate the soil to an average depth of about 1 m. Most lateral root growth occurs in the top 30 cm of soil during the second year.