Blueweed

Blueweed is a common invasive plant in central and south-central areas of British Columbia. Native to Eurasia, blueweed is well adapted to dry, rocky or shallow soils. Blueweed can survive in a variety of soil types and pH, but does not tolerate shade and requires well drained soils. Blueweed prefers warm, southern aspects. Blueweed can be found on roadsides, drainage ditches, right-of-ways, fence lines, pastures, rangeland, and other disturbed areas.  

• Blueweed invades pastures and rangelands, replacing forage plants.  
• Blueweed contains pyrrolizidine alkaloids, which can be toxic to livestock if ingested. Symptoms can include constipation or diarrhea, anorexia, lethargia, and a general loss of condition with the animal getting progressively weaker. More severe symptoms are changes in behavior, wandering, and liver failure.  
• Blueweed can also cause skin irritation in humans, so gloves should be worn if handling this plant.  
• Blueweed’s ability to compete with native plants in B.C. is unknown.  

The most effective way to ensure that your lands do not become infested with blueweed is by prevention. Here are some recommendations to prevent blueweed from invading your property: 

• Remove plant seeds from personal gear, equipment, vehicles and machinery at designated cleaning stations before leaving infested sites.  
• Maintain your crops and natural lands in a healthy, vigorous condition to ensure a competitive plant community; competitive perennial grasses and forbs utilize water and nutrients that would otherwise be readily available to blueweed.
• Regularly patrol your property for blueweed plants and immediately control or remove infestations before seed set. Do not leave plants to compost as they may still produce viable seed.  
• Cooperate with adjacent landowners and encourage them to prevent blueweed spread. 
• Immediately re-vegetate disturbed, bare soils with a suitable seed mixture that provides dense, early colonization to prevent weed invasion.  
• Do not move contaminated soils to a new area.  

• Hand-pulling may be an effective control for small infestations; cutting or mowing larger infestations will decrease seed production.  
• Due to the ability to re-sprout, multiple treatments will likely be required to deplete root reserves to the point where flowering and seed production are unlikely.  
• It is important to monitor treatment success over following years.  
• Chemical control is also an option. Recent herbicide trials have shown that fall treatment is more effective than spring treatment. Before applying herbicides, read the label for full use and precautionary instructions.  
• For further information on the selection and application of chemicals to protect your crop, contact AgriService BC at 1-888-221-7141 or email AgriServiceBC@gov.bc.ca  
• Currently, there is no biocontrol agent available for blueweed in BC.