Culture
Easily grown in moderately fertile, moist but well-drained soils in full sun. Tolerates highly alkaline soils, but achieves best growth in moderately alkaline to neutral soil conditions. As a biennial, it produces large, taprooted basal rosettes in the first year and flowers with subsequent seed production in the second year followed by plant death. Sow seed in spring or late summer in rich, well-drained soils in full sun. Readily self-seeds in the landscape.
Noteworthy Characteristics
Isatis tinctoria, commonly called woad, dyer’s woad, or pastel, is a short-lived perennial or biennial of the mustard family. It typically grows in the first year as a large-taprooted basal rosette to 12” tall, with branched, alternate-leaved flowering spikes rising above the basal rosette in the second year to 2-4’ tall. This plant primarily features alternate leaves, yellow flowers, pendant brown seed pods and a blue dye which can be extracted from the foliage. It is native to Europe and southwestern Asia. It was brought to Plymouth Colony in the early 1600s by European immigrants, and over time has been distributed to and naturalized in parts of northeastern Canada, New England and western North America from British Columbia and Montana south to California and New Mexico. In the western U.S., it is commonly found today in a variety of habitats including rangelands, agricultural lands, pastures, fields, roadsides and disturbed sites.
Foliage consists of basal rosettes of stalked, oblong-lanceolate, gray-green leaves (each to 2-4” but sometimes to 7” long) and stalkless, smaller, alternate, arrow-shaped, gray-green leaves (each to 2” long) borne on leafy flowering stems rising above the basal foliage in the second year to 4’ tall. Four-petaled yellow flowers (each to 3/8” across) bloom in early summer in loose 3-inch long racemes which collectively form a large terminal panicle. Flowers are followed by dark pendant decorative seed pods. Leaves produce a blue pigment.
Woad has been grown as a dye plant for its indigo blue pigment since the Stone Age and has been additionally cultivated for its medicinal properties in Europe since the 1200s. This plant was the sole source of a quality blue dye used in Europe from ancient times (e.g., cloth dye or body paint used by the Britons and Celts) until Indigofera tinctoria (true indigo) became available from the Orient as a less expensive, competing source. The blue pigment is obtained from woad leaves by fermentation and oxidation of a colorless glucoside known as indican. Indican is also present in the leaves of the unrelated true indigo which was brought by land to Europe from Asia beginning in Greco-Roman times, but did not become a significant competing source to woad in Europe until Vasco de Gamma discovered the sea route from India to Europe. By the mid-1600s, true indigo largely replaced woad as the blue dye of Europe. The chemical blue dye extracted from woad is commonly called indigo which is the same blue dye, albeit in stronger concentrations, that is extracted from true indigo.
Notwithstanding its blue dye properties, woad was also used in times dating back to ancient Greece and Rome where plants were used for a variety of medicinal purposes including antiseptic wound treatments, fever reduction, and ulcers.
Genus name is the classical Greek name for this plant. It was cultivated in Britain up to about 1930 for production of a blue vegetable dye. It is much less in demand today for commercial dye purposes because of the creation of synthetic dyes which have now taken its place, as well as the place of Indigofera tinctoria, as a main source of blue dye.
Specific epithet from Latin means used in dyeing.
Woad is a common name for this plant plus the name of the blue dye extracted from the leaves of the plant.
Problems
No serious insect or disease problems. Susceptible to club root.
Uses
Wild gardens. Herb gardens.