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Dyers woad (Isatis tinctoria)
ODA rating:B
Other common names
Asp of Jerusalem
Description
Dyer's woad is a perennial or biennial that grows up to three feet tall. It has multiple stems that arise from the base. Foliage has distinctive blue-green cast with whitish glaze. The upper leaves are smaller and clasp the stem with ear like projections. Flowers are bright yellow, small and in clusters. Flowers have four spoon shaped petals. Fruits pods are flat and black or purplish brown. Flowering and the most vigorous growth will occur mainly in sandy, gravelly soils, and in marginal farmlands. Invades rangeland, grain fields, pastures, waste areas, roadsides, and fencerows. It can also be found in orchards and in rows of cultivated crops. Flowering and the most vigorous growth will occur mainly in sandy, gravelly soils, and in marginal farmlands. Invades rangeland, grain fields, pastures, waste areas, roadsides, and fencerows. It can also be found in orchards and in rows of cultivated crops.
Impacts
Dyer's woad forms dense stands in rangelands that crowds out native vegetation. This plant is highly competitive and often grows in dense colonies. It reduces forage availability by suppressing annual grasses and is low in palatability to grazing animals. It is allelopathic properties inhibit the growth of other plants around it.
Click on image to view larger photo.
 Image courtesy of Bonnie Rasmussen, Oregon Dept. of Agriculture. |  Image courtesy of Dan Sharratt, Oregon Dept. of Agriculture |  Image courtesy of Dan Sharratt, Oregon Dept. of Agriculture.
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Introduction
Dyers woad is native to Europe. it was introduced into the United States as a source of blue dye. Established in Virginia in colonial times. Its distribution in eastern United States is spotty. It has become widespread in the western part of the country. Its resurgence as a popular dye plant may greatly extend its range throughout the United States
Distribution in Oregon
Map legend
Yellow: limited distribution in county Red: abundant in county Grey: not known to be present in county
Biological controls
There are currently no biological control agents available for this plant but there is currently research being done on several that will possibly be available in the future.
Informational Links
WeedMapper
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