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Report an Invasive Species

Mountain bluet

Mountain bluet

Mountain bluet

(Centaurea montana )

Priority: -  Control

Tags: Terrestrial

Identification and Reproduction

Identification: 

  • Also known as montane knapweed, this plant is a perennial cornflower. 
  • Typically mountain blue knapweed will grow between 30-80 cm tall. 
  • Stems grow upright, slightly branched and covered in hairs. 
  • This plant has wide to lance shaped leaves which are winged near the stem. Their undersides are covered in small hairs. 

  • Flowers are encased in black fridged bracts; disk flowers are blue but in some conditions can grow white. Blooms occur from May through August. 

Reproduction: 

  • Produces seeds and spreads vegetatively through creeping rhizomes. 
  • Like other knapweeds it also is a prolific seed producers. 
  • Seeds have a long viability. 
  • New plants can also sprout from root fragments. 

Habitat & Ecology

  • Commonly takes over open areas, forests and along road sides. 
  • This knapweed does best in sunny, exposed locations. 
  • Well adapted to soil textures and pH levels. 

Impacts

Social: 

  • This plant can out-compete natural forage species and can then decrease food availability for livestock. 

Ecological: 

  • Spreading quick and forming dense stands they can displace native plants. 
  • Since it has a long growing period it out-completes native vegetation. 
  • Mountain bluet also alters native plant-pollinator relationships as they can bloom earlier than native species. 

Management

Mechanical/Manual Control: 

  • Prior to seed production, pulling, cutting or mowing will be effective. 
  • If done while flowers are present be sure to properly dispose of plants, preventing dispersal of viable seeds. 
  • The root system should also be fully removed to reduce re-establishment.
  • Continuous annual treatments will be needed since mountain bluet has long seed life. 

Chemical Control: 

  • Currently picloram, dicamba, 2,4-D, clopyralid, aminopyralid and glyphosate are registered as effective herbicides on this plant. 
  • It is recommended to wick or select spot spray plants. 
  • Please carefully read herbicide labels prior to application. 

For alternative planting options to mountain bluet check out Plantwise tips page here

Resources

Download the Invasive Species council of BC's Factsheet on Mountain Bluet here

Header photo (Bernt Fransson).