Dyers Woad (Isatis tinctoria)

County Management Strategy: Eradication throughout the County.

Identification: Woad is an annual or short lived, tap rooted perennial mustard growing up to 48 inches high. The tap root may reach to a 5 foot depth. Leaves are bluish-green, lanceolate (strap shaped) and are connected to the stem by a petiole. The leaf has a whitish nerve or vein visible on the upper surface. Flowers are numerous, yellow and very small. The seed pods are very diagnostic, being extremely large for a mustard, flattened and very dark. Each pod contains a single seed.

Other names: Woad

Similar Species: Many mustards have yellow flowers and similar leaf structure. The large black seed pods are the best way to tell this from other mustards.

Control Timing: During the rosette stage (fall or spring) and before flowering.

Control Target: Prevent seed production.

Control Methods: Manual removal is usually a good method for annual plants. However, dyer’s woad will regenerate from its tap root if the root is not completely removed. Rosettes should be killed manually or with herbicides in the spring or fall. Plants that are bolting should be removed manually or sprayed as soon as possible.

Status in Mesa County: One plant was found in the dye garden at the Botanical Gardens in Grand Junction; it was removed. It is a serious and expanding problem in Utah. REPORT INFESTATIONS TO THE DIVISION OF PEST MANAGEMENT!

Photos:
http://www.invasive.org/species/subject.cfm?sub=4587

Fact sheets and control:
http://mtwow.org/dyers-woad.html
http://www.colorado.gov/cs/Satellite?c=Page&cid=1184920449131&pagename=Agriculture-Main%2FCDAGLayout

Additional Links:
http://www.usgs.nau.edu/swepic/asp/swemp/unified.asp?Symbol=ISTI