Dyer’s Woad (State designated weed)
- Isatis tinctoria
- Brassicaceae (Mustard family)
Dyer’s woad is a Colonial era plant introduced from Europe. It typically appears first along roadsides and at disturbed sites, then spreads by seed to rangelands and croplands.
Growth Habit: Winter annual, biennial or short-lived perennial; 1 to 4 feet tall.
Leaves: Spoon-shaped, long and pointed, alternate, bluish-green with a whitish nerve on the upper surface.
Flowers: Stems are topped by masses of yellow, four-petaled flowers, quite airy and delicate. Each flower grows into a long oval seed pod containing one seed. Seed pods hang down and turn black or purplish brown.
Root: Thick taproot that can exceed 5 feet in depth.
Status: State Designated Noxious Weed, Category 1 Fremont County. Rare, no tolerance, with a goal of early detection and eradication. Call FCWP if you detect this species.
Control: Dyer’s Woad will grow from its taproot even if the top of the plant is cut away, so for mechanical control it is important to dig up as much of the root as possible. Herbicides are effective, especially in the rosette to early blossom growth stage. FCWP offers a 40 percent Cost Share on chemicals for controlling this species. Contact your local weed and pest office for further treatment recommendations.
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