Dyer's Woad

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Description:

DYERS WOAD - Isatis tinctoria L.

Brassicaceae - (Mustard family)

Dyer's woad is a winter annual, biennial or short-lived perennial; 12 to 48 inches in height. Leaves of dyer's woad are alternate, simple, petiolate, bluish-green with a whitish nerve on the upper surface of the blade. The inflorescence has a flat top, petals yellow; fruit a pod, indehiscent, black or purplish brown and one-celled, containing a single seed.

Dyer's woad was introduced from Europe. It made its first appearance in the United States in colonial times. It has a thick tap root which may exceed 5 feet in depth. Once leaves are removed mechanically, plants will regenerate from roots. Dyer's woad is first found along roadsides and disturbed sites and spreads from there to rangeland and cropland by seeds from late spring to mid-summer.

(Courtesy of Weeds of the West)

Control Strategies:

A small stand of this weed was discovered in the Lander area in 2004.  Monthly throughout the growing season, we pull every plant that is found.

Dyers woad is hard to manage. The deep roots make it hard to pull by hand, and it spreads quickly. Escort and Telar at 0.75 ounces per acre are equally effective in controlling this weed, but on rangeland sites there will also be a lot of damage to desirable species. Treat this weed as soon as you find it to avoid later treatment conflicts.

To learn about biological control agents for Dyer's Woad visit this link.