Photo credit: Steve Dewey, Utah State University, Retrieved from Bugwood.org (Image Number: 1459931), used under CC BY 3.0 US, modified from the original
Common Name: Dyer's Woad
Scientific Name: Isatis tinctoria
Habitat: disturbed areas, roadsides
Provincial Designation: Prohibited Noxious
Prohibited Noxious weeds are plant species designated in the Alberta Weed Control Act. Prohibited noxious weeds must be destroyed when found, meaning all growing parts need to be killed or the plant's reproductive mechanisms need to be rendered non-viable.
Dyer's woad is native to southeast Russia and central Asia. It was introduced to eastern North America in the 17th century as a medicinal herb and source of indigo dye.
A single Dyer's woad plant can produce as many as 10,000 seeds per year. This plant can invade crop fields and grassland and out-compete native species. It reduces yields of crops and forage.
This weed has small yellow flowers with four petals arranged in a cross-shape. All the Brassica (mustards and cabbage) species - the family that Dyer’s Woad is in - have 6 stamens (male parts): 4 tall and 2 short.
Basal leaves have long stalks but stem leaves are sessile (grow directly from the stalk) and clasp the stem. All leaves are blue-green in colour and have a distinctive cream-colored midrib.
The plant grows up to 120 cm tall with a heavily branched upper portion.
Can Be Confused With ...
Mustards - Brassica species - there are many wild mustards in Alberta, and commercial crops of both mustard and canola. Dyer’s Woad has unique shaped seed pods - winged, paddle shaped hanging from the stalk.
Learn more about this species:
See Fact Sheet - Alberta Invasive Species Council