Dyer's Woad
Scientific Name: Isatis tinctoria

History/Origin
          Dyer's woad is native to southeastern Russia and currently exists on six continents. Anciently, it was believed to have medicinal properties and warriors used it to paint themselves with the blue extract. Later, it was grown and used as a textile dye and was transported from Europe to America for that purpose. In the early 1900's, It was introduced into the West as a contaminant in alfalfa seed.

Biology/Ecology
          This member of the mustard family produces an average of 350-500 seeds per plant, with some plants producing well over 10,000 seeds in one year. In one instance, a population of dyer's woad grew from two acres to 100 acres in two years, just by seed dispersal and establishment. The seeds alone show little dormancy, but seeds left in the fruit may persist. Dispersal by wind is limited, except for those that may be moved along the surface of the snow. Most long-range dispersal occurs by vehicle, flowing water, birds, and contaminated feed.

          This plant starts out as a low-lying rosette. Winter chilling is necessary for the plants to bolt and produce the beautiful dome of bright yellow flowers. Average stem growth during the bolting stage has been measured at a rate of four inches per week. Flowering is seen as early as April, with seeds maturing in June or July. Dyers woad produces a tap root 3-5 feet long.

Known Impacts
Detrimental:
          Loss of forage, alteration of natural plant community

Beneficial:
          Used as a blue dye in textiles

Potential Locations
          Dyer's woad doesn't need a human disturbance in order to invade a site. Although it prefers rocky soil with limited water holding capacity, it is very prolific and will grow in a variety of places. It can be found in rangelands, forests, grain fields, pastures, waste areas, roadsides, orchards, and in cultivated row crops.

Control/Management
          Once again, multiple tools can and should be used in the control of dyer's woad.
• One of the simplest and most effective control methods is hand-pulling. In parts of Utah this method has been used by high school students and other volunteers. This is most effective with small populations and should be done 2-3 times a year for several years to be effective. It is safe to leave the pulled plants on site if there are yellow flowers still attached to the plant (green seed pods may be visible). If flowers are not present, the seed are developed enough to germinate. These plants should be hauled to the dump.
• A biological control agent (a rust known as Puccinia thlaspeos) has been found to be effective in keeping dyer's woad populations in check.
• Herbicide application is most effective in the rosette stage (example herbicides: 2-4,D, Escort, Ally, Telar [look at herbicide label: free search]).