Isatis tinctoria L.
Dyer’s woad is a biennial mustard that grows up to 3 feet tall. The stem is waxy and varies in color from blue-to-purple green. The leaves are long and simple with prominent white veins. The yellow flowers have four petals and occur in clusters toward the top of the plant. The seed, its primary mechanism of spread, is ½ inch long, oval, flat, and black to brown. Each seed pod only contains one seed. This plant’s tap root make it easy to control mechanically, but make sure to wear gloves whenever pulling any noxious weeds.
Dyer’s woad was likely introduced into the U.S. during the 1700’s for its use in producing a blue textile dye. Dyer’s woad in Teton County is at relatively low numbers, but continues to be found in new locations. Most infestations come from the south end of the county in the Snake River Canyon, as well as along the Moose-Wilson highway.
If you find this weed on your property or around Teton County, please report it immediately at 733-8419.