Identifying and Managing Dyer's Woad (Isatis tinctoria) in Pastures, Rangelands, and Non-Crop Settings
woad woe
Figure 1. Dyer's wood infestation at
full bloom. Flowering usually occurs by
late spring.

Quick Facts

  • Dyer’s woad outcompetes perennial forbs and grasses.
  • Seeds are viable as green pods (fruits) appear.
  • It’s adapted to many environments. 

Introduction

Dyer's woad (Isatis tinctoria) was introduced into Utah during the mid-19th century as a source of indigo dye. The plant escaped cultivation and has spread across rangelands, foothills, and other sites throughout the Intermountain West (Figure 1).

 

Identification

figure 2 - white midvein
Figure 2. Yellow arrows indicate the
white midvein and alternating pattern
of dyer's woad leaves.

Dyer’s woad leaves are lance-shaped with a white midvein on the upper surface of the blade. The leaves alternate up the stalks of mature plants (Figure 2). 

Flower stalks form a flat top with many small yellow flowers. Petals and sepals are arranged in X patterns (Figure 3).

Mature fruits are pods containing a single seed. Young pods are lime green but turn dark purplish-brown as they mature. Dyer's woad has a thick, deep-growing taproot. Mature plants at flower may have purple stems (Figure 4). 

Lifecycle and Distribution

Dyer’s woad is a winter annual, biennial, or a short-lived perennial. Plants spread by seed, which become viable relatively soon after flowering (Young & Evans, 1971).

Dyer's woad flowers, with dashed lines marking the X pattern of petals.
Figure 3. Dyer's woad flowers, with
dashed lines marking the X pattern
of petals. 

Seeds germinate with the onset of fall, cooling temperatures, and where soil moisture is adequate. Seedlings often form a rosette the first year, then flower and set seed the following year (Figure 5).

Dyer's woad is abundant on Utah hillsides and valleys. The plant is well adapted to disturbed areas, rangeland, dry woodlands, fence lines, and other areas. Dyer's woad is a nuisance because it replaces native vegetation, resulting in livestock and wildlife avoidance or overgrazing of the remaining desirable plants, with the exception being grazing by small ruminants while plants remain immature.

Fortunately, other than the sheer number of acres infested, the weed is rather benign compared to some of the other widespread noxious weeds. In Utah, dyer's woad is a Class 2 noxious weed; namely, high priority for control (Lowry et al., 2012). 

Mature dyer’s woad plant in bloom.
Figure 4. Mature dyer’s woad plant
in bloom 

Management

Prevention is always the preferred method to manage noxious weeds. Periodically, scout areas where new infestations are likely to occur, for example, fence lines, right-of-ways, cultivated land, and ditch banks. When choosing fill material, ensure that the source of the material is clean and free of weeds. Transport weed-free hay and feed horses and livestock weed-free hay prior to transporting them off of your property. Carefully clean equipment, tools, clothing, and footwear upon exiting infested areas. 

Additionally, good cultural practices when farming or landscaping will help with management. Planting competitive crops or maintaining healthy plant cover in hay and pastures will limit dyer’s woad establishment and impacts. In new developments and residential areas, landscape early with plants that are well adapted to the area. Weed barriers and mulches are also useful. 

Mechanical removal is accomplished by pulling, hoeing, cultivation, or mowing. Pulling the plant up or ground cultivation is much more effective for smaller areas than hoeing or mowing. For larger plants or in large infestations, cutting the taproot to at least one shovel spade deep may be more efficient. Be mindful of maturing fruits as the flowers die (Figure 6). If fruits are present, bag the plants to prevent seeds from spreading. 

Mowing is not particularly effective, but it can help if done early enough in the year. The plant will continue to make flower heads on much shorter stems after mowing. Follow-up cuttings may be needed.  

Dyer's woad rosette
Figure 5. Dyer's woad rosette
surrounded by smaller seedlings
developing into rosettes.

Biocontrol is the process of introducing a natural predator or pathogen to control a pest. No known weed-feeding insects specific to dyer's woad have been identified at this time. However, Puccina thlaspeos (Figure 7), a fungus, demonstrates minor promise as a biocontrol agent (Lovic et al., 1988). This rust fungus may reduce plant vigor and seed production but won’t control dyer’s woad alone. 

Table 1. Summary of Non-Herbicide Options
Control Method Notes
Prevention
  • Practice early detection and rapid response. Inspect properties frequently and remove new dyer’s woad plants before they become problematic.
  • Clean and remove the plant and soil residue from people, pets, livestock, and equipment upon exiting infested areas.
  • Feed horses and other livestock weed-free hay for three days prior to moving animals off of your property. 
  • Transport clean fill (manure, mulch, topsoil, gravel, road base, etc.)
  • Prevent existing dyer’s woad plants from producing seed.
  • Plant quality (weed free/certified) crop seed.
Cultural and mechanical (pasture) 
  • Plant forages that are well adapted to the location of the pasture and management practices. 
  • Do not overgraze pastures. The general rule is to not utilize over 50% of the plant.
  • Maintain proper stocking rates to encourage an even utilization of the forage.
  • Maintain a weed-free pasture; dig or pull dyer’s woad as plants arise.
  • Plant in the fall to establish cool-season grasses before warm-season annuals germinate. 
Cultural and mechanical (rangeland) 
  • Do not overgraze. The general rule is not to utilize over 50% of the plant.
  • Maintain proper stocking rates to encourage an even forage utilization.
  • Dig or pull individual dyer’s woad plants before flowering.
  • Seeding of desirable plants should occur in the fall.
Cultural and mechanical (non-crop) 
  • Cultivate and work the ground where appropriate before weeds mature.
  • Mow plants after bolting and before they flower.
  • Follow-up cuttings may be required.
Biocontrol
  • P. thlaspeos can be observed infecting random plants naturally but has not been effective when tested as a treatment. 
A closeup of immature fruits.
Figure 6. A closeup of immature fruits.
At this stage of maturity, fruits may
contain viable seed.   

Chemical Control

When used appropriately, herbicides can be an effective method to kill or prevent dyer’s woad (see Table 2). 

Always read and follow the label when applying chemical herbicides. Pay special attention to safety requirements, restrictions of use, directions for use, and disposal requirements. 

The location of application and the uses specified on the herbicide label will determine which herbicides are appropriate.  

Be aware of surroundings, e.g., open water, slope, vegetation nearby, temperature, and wind when applying chemical herbicides.

Preemergence herbicides prevent seedlings from emerging. These herbicides are usually nonselective to seedlings and prevent most annual and perennial seeds from establishing. When used appropriately, these chemicals can be used to stop new woad plants from sprouting among desirable perennials.

Postemergence selective herbicides will kill certain types of plants, e.g., broadleaf weeds or grasses. Selective herbicides work well when dyer’s woad is growing in grass pastures and on rangeland. They also can be used in many non-crop settings.  

Active Puccina
Figure 7. An active Puccina thlaspeos
infection. Note the rust-colored
spores.  

Postemergence non-selective herbicides kill most or all actively growing plants, regardless of plant classification. Non-selective herbicides are useful in areas where vegetation is discouraged or for seedbed preparation.  

Pasture

Good grazing practices are essential to maintaining a healthy pasture. Likewise, herbicides are effective tools for maintaining a healthy pasture.  Some products labelled for selective control of broadleaf weeds can provide effective dyer’s woad control in permanent grass pastures, but they are not suitable for grass-legume mixed pastures as many herbicides labeled for pasture can injure or kill the legumes. In these situations, using preemergence herbicides, specifically labelled postemergence herbicides, spot treatments, or omitting chemical control are the only options available. 

hillside plants
Figure 8. Large infestations decrease
biodiversity as seen in this hillside
plant community.  

Rangeland

Management of weeds on rangelands is important for maintaining the resource (Figure 8). Before applying herbicides, caution should be taken to be aware of your environment, e.g., slopes, aquatic areas, and sensitive plant species. Research at Utah State University (USU) has shown that specific herbicides are effective at controlling different life stages of dyer’s woad. In research plots, 2,4-D was effective against seedlings the year it was applied and weak on rosettes while Escort was effective against seedlings and rosettes.  However, neither effectively controlled seedlings germinating the following spring. A new herbicide labelled for use in range (indaziflam) showed excellent suppression of dyer’s woad seedlings the spring after treatment. 

Non-Crop

Examples of non-crop areas include but are not limited to the following sites: gravel areas, loading ramps, storage yards, vacant lots, railroad and rail yards, managed roadsides, fence rows, utilities, and parks. Ensure that the site being treated is approved on the label.  

For complete vegetation control involving dyer's woad, herbicides labeled for preemergence and postemergence use in non-crop settings can be cost effective for large acreages, such as roadsides and fences.  

Dyer's woad next to irrigation ditches and streams must be treated with care using only certain herbicides that are labeled for aquatic use. 

Table 2. Summary of Herbicides 
Mode of action Active ingredient Trade name Comments
Pasture
(Many products in Table 2 are labeled for pasture and rangeland, but restrictions are site-specific. Refer to the label.)

Group 2
ALS Inhibitors 

 imazapic  Plateau  Provides good control for seedlings, rosettes, and bolting plants. Some residual control the following year. Applications > 4 oz/acre may temporarily suppress grass growth. 
Group 2 
ALS Inhibitors 		 metsulfuron Escort, MSM 60, etc.  Provides excellent control for seedlings, rosettes, and bolting plants. No residual control the following year. These products may temporarily suppress grass growth. 
Group 2 
ALS Inhibitors		 chlorsulfuron  Telar  Typically applied postemergence with some residual the next year. May temporarily suppress grass growth.
Group 4
Growth Regulators* 		 2,4-D  Several names  Good control for seedlings and young rosettes. No residual control the following year. Pay special attention to the label to prevent drift. Avoid spraying 2,4-D when temperatures  > 80°F. 
Rangeland
(All products listed under Pasture can be used in rangeland. Refer to the label for specific instructions.) 
Group 29
Cellulose Biosynthesis inhibitor		 indaziflam  Rejuvra  Newly registered herbicide (applied preemergence) can prevent seedling establishment and is very active on invasive annual grasses. Also prevents establishment of desirable seed; only use in areas where sufficient perennial plant cover currently exists. 
Non-Crop
(Many products in Table 2 are labeled for sites other than pasture and rangeland. Restrictions are site-specific; refer to the label.)
Group 9 Aromatic amino acid inhibitors  glyphosate  Many names Non-selective herbicide, which kill desirable plants--especially grasses. Good control of emerged seedlings and rosettes.  
Group 29 Cellulose Biosynthesis inhibitor  indaziflam  Esplanade  Newly registered herbicide (applied preemergence) can prevent seedling establishment and is very active on invasive annual grasses. Also prevents establishment of desirable seed; only use in areas where sufficient perennial plant cover currently exists.

*Except for 2,4-D, most other growth regulator herbicides (i.e., triclopyr, aminopyralid, picloram) provide minimal control of dyer’s woad.

Picture Credits

Utah State University Extension and authors provided all photos. 

References

  • Lowry, B. J., Ransom, C., Whitesides, R., & Olsen, H. (2017). Noxious weed field guide for Utah. All Current Publications. Paper 1352. Utah State University Extension.  https://digitalcommons.usu.edu/extension_curall /1352  
  • Lovic, B. R., Dewey, S. A., Evans, J. O., & Thomson, S. A. (1988). Puccinia thlaspeos —A possible biocontrol agent for dyers woad. Proceedings of the Western Society of Weed Science, 41, 55–57.
  • Young, J. A., Evans, R. A. (1971). Germination of dyers woad. Weed Science, 19, 76–78. 

Published June 2021
Utah State University Extension 
Peer-reviewed fact sheet

Authors

Cody Zesiger, Utah State University Extension assistant professor; Jacob Hadfield, Utah State University Extension assistant professor; Corey Ransom, Utah State University associate professor and Extension weed specialist 

Cody Zesiger

Cody Zesiger

Extension Assistant Professor | Agriculture & Natural Resources | Weber, Morgan and Davis Counties

Agriculture and Natural Resources

Phone: 801-399-8208
Office Location: Weber, Davis, and Morgan Counties
Jacob Hadfield

Jacob Hadfield

Extension Assistant Professor | Agriculture and Natural Resources | Utah and Juab Counties | Juab County Director

Agriculture and Natural Resources

Phone: (435) 623-3457
Office Location: Utah and Juab Counties
Corey Ransom

Corey Ransom

Weed Specialist

PSC Dept

Phone: (435) 797-2242
Office Location: Logan Campus

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