mcpeaks
BLM
U.S. DEPARTMENT OF THE INTERIOR
BUREAU OF LAND MANAGEMENT
Spotted knapweed. Salt cedar. Leafy spurge. Musk thistle. Dalmation toadflax.
Wyoming
BLM>Wyoming>Programs>Weeds & Pests>Species>Dyers woad
Print Page

Dyer's Woad 

 

 

Dyer's Woad.

Dyer's Woad.

Dyer's Woad close-up.

Interesting Facts

  • It was introduced to the eastern United States in the 17th century as a source of indigo dye and as a medicinal herb.
  • Plants can produce as many as 10,000 seeds per year.
  • Has a thick tap root that can exceed 5 feet in depth.

Description

A stout, erect winter annual, biennial, or short-lived perennial in the mustard family.

Stems Erect, somewhat woody, ranging in height up to 4 feet.

Leaves have a distinct cream-colored midrib and powdery white film on the upper leaf surface.

Flowers are small and yellow (3mm in width), located in dense, flat-topped racemes. Each flower has the four petals in a cross-shape characteristic of the mustard family.

Seed/Fruit are purplish-brown, tear-drop shaped, winged and pendulous.

Habitat

Dyer’s Woad thrives in light sandy to gravelly soils and will even grow in rocky soil.

Unlike other mustards, it does not require disturbance to become established.

Ecological Impacts

Dyer’s woad impacts the natural plant communities by outcompeting native plants. It causes a loss of wildlife and livestock forage by displacing native grasses and other native species. It is unpalatable to livestock, but not toxic.

Control

Mechanical: Cultivation of the rosettes prior to bolting and flowering can eliminate newly established populations. Mowing is less effective due to the woody stems and the ability of the plants to resprout from the crown.

Chemical: Chlorsulfuron and metsulfuron methyl are effective if applied at the bolt to bud stage of growth in the spring and early summer.

Biological: A native rust pathogen, Puccinia thlaspeos, readily infects the rosettes of Dyer’s Woad. However symptoms are rarely obvious until the second year.