DYERS WOAD - Isatis tinctoria L.

Brassicaceae - (Mustard family)

Dyer’s woad is a Colonial era plant, and a member of the mustard family.
The rosette leave are spoon shaped maturing into a robust 48 inch plant with stems that are often pinkish red.  Stem leaves are long, thin, and pointed, with sharp “ear lobes” hanging down next to the stem.  Leaves get fewer and smaller as they go up the stem; all leaves have a prominent white mid vein.
The stems are topped by masses of yellow, 4 petaled flowers, quite airy and delicate.   Each flower grows into a long oval seed pod containing one seed.  The seed pod, which hangs down, turns black and is very visible from a distance.
Dyer’s Woad will grow from its’ tap root even if the top of the plant is cut away.  Control is important as it becomes an aggressive weed and is of no use as animal feed.  This plant destroys competition by producing a chemical that prevents the growth of other plants close by. It is often used as an ornamental plant.

The following is courtesy of Weeds of the West:

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)

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