Dyer’s Woad

Isatis tinctoria L.
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Status:
State Designated
•
Priority 1
Synonyms:
glastum

Description

Dyer’s woad is a biennial or short-lived perennial forb in the Brassicaceae (mustard) family. It grows from a taproot to form a basal rosette in its first year; in subsequent years it produces an erect stem that reaches 1 to 4 feet tall. Stems are frequently branched near the top. Basal leaves are elongated and have fine hairs. Stem leaves occur alternately on the stem, are hairless, and have lobes at the base that clasp the stem. All leaves have a prominent white midvein. Dyer’s woad flowers from late spring to early summer. Flowers occur in panicles at the end of branches. Individual flowers are yellow and small (~⅛ inch across) and have four petals. Seeds are distinctive. They are produced in ½ inch long, pear shaped, black winged pods that droop from the branches.

Origin and Spread

Dyer’s woad is native to Eurasia where it was cultivated as a source for indigo dye beginning in the 13th century. This species was intentionally introduced to North America through the Plymouth Colony. Further spread throughout the continent was both intentional (in Utah for use as dye), and accidental (in the western region as a contaminant in alfalfa seed). Seeds are primarily dropped near the parent plant, but they are also dispersed to new locations by animals, humans, or water. It can be found in a variety of habitats including riparian areas, disturbed sites, rangeland, and forest systems.

Management Options

Prevention and cultural control strategies should be utilized as much as possible.

There are not any biological controls for dyer’s woad currently available, but several trials are ongoing.

Because dyer’s woad has a taproot, it can be readily managed by hand pulling or digging out the root. Controlled grazing by goats can successfully eliminate plants when conducted early in the growing season. Repeated mowing after bolting and before seed production can prevent seed production; mowing two weeks after an herbicide application is particularly effective at killing the root and preventing seed production. Do not mow while seeds are present.

Larger infestations can be controlled with herbicides. Spring treatments of rosettes or early bolting plants are recommended.

Treatment Area Recommended Herbicides
Range, Pasture, Natural Areas chlorsulfuron
Pasture where manure or hay will be used for compost chlorsulfuron
Lawn 2,4-D
Riparian glyphosate (aquatic label)

Additional Resources