Dyer's Woad
Dyer's Woad Rosette
Dyer's Woad Seed

Brassicaceae or Mustard Family
Isatis tinctoria

IDENTIFICATION:
Growth Habit:
Winter annual, biennial, or short-lived perennial, grows 1-3 feet tall.
Leaves: Rosette leaves are widest near the tip and covered with soft hairs. Stem leaves usually lack hairs and teeth on the margins. Bluish-green leaves with white midrib on upper leaf surface are alternately arranged, lance-shaped and clasp the stem with short basal lobes.
Stems: Long slender stalks
Flowers: The four yellow petals of an individual flower are arranged in a cross formation and are 1/8 inch long and wide. Flowers cluster on the upper portion of the stem, creating a dens flat-topped inflorescence.
Roots: 3-5 foot long taproot and some lateral roots in the upper 12 inches of the soil.
Seeds: Purplish-brown, teardrop-shaped seed pods that hang from small stalks. Plants may produce 350 to 500 seeds each, but selected plants have been known to produce more than 10,000 seeds in one year.
Reproduction: By seed.
Habitat: Roadsides, railroads, disturbed sites and spread from there to rangeland and cropland by seeds.

MANAGEMENT OPTIONS:
Handpulling: Repeated handpulling treatments have been very effective in managing infestations of dyer's woad in Montana. First treatment should occur when infestation is close to full bloom, with a second treatment occuring three to four weeks later to catch any individuals that were missed the first time or have re-sprouted. The root crown and most of the taproot must be removed in order for handpulling to be effective. All flowering plants must be placed in plastic bags and removed from the site. Pulling is most effective when soil is moist.
Mowing: Mowing has the potential to be an effective method of control if done when plants have begun to form seed pods, but prior to the plant forming more than 75% of its seed pods.
Biological Control: N/A
Grazing: Grazing is not an effective method of control for dyer's woad because the intensity of grazing required tends to do more damage to competitive desirable plant species than to the dyer's woad infestation.
Herbicides: The following herbicides have been labelled for control of dyer's woad. Always consult product labels and read them carefully to ensure correct species/land management usage and chemical application.

Trade Name:  Active Ingredient:  Rate:  Efficacy:  Comments: 
 Escort metsulfuron  1 oz/acre  most effective if used when plant is in rosette to bud stages with a non-ionic surfactant  Cannot be used near wells, surface water or shallow ground water
 Telar  chlorsulfuron  1 oz/acre most effective if used when plant is in rosette to bud stages with a non-ionic surfactant   
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