SafePlants

Squarrose Knapweed (Centaurea virgata)

Squarrose knapweed is a perennial plant known for its weedy nature, particularly in rangeland environments. Understanding its characteristics and distribution can help in its management and control.

Considerations for Pets

• Leaves are deeply dissected.
• Flowers are pinkish or purple colored.

Scientific Name and Taxonomy

• Scientific Name: Centaurea virgata Lam.
• Common Name: Squarrose Knapweed
• Family: Asteraceae (also known as Compositae, the sunflower family)
• Subspecies: Centaurea virgata ssp. squarrosa (Willd.) Boiss.
• Synonyms/Alternative Scientific Names:
  • Centaurea virgata Lam. var. squarrosa (Willd.) Boiss.
  • Centaurea virgata Lam ssp. squarrosa Gigl.
  • Centaurea squarrosa
  • Centaurea triumfetti

Distribution and Habitat

• Native to the eastern Mediterranean area, southwest Asia, and the Middle East.
• Introduced to North America, where it has become weedy.
• Specifically mentioned as weedy in northern California and Utah.
• Also found in the Klamath and Cascade Ranges, Modoc Plateau, and northern Sierra.

Ecological Role

• Considered a competitive rangeland weed.
• Highly competitive and noxious.
• Can significantly impact landscapes, as noted in Utah in the 1950s.

Morphological Characteristics

• Perennial forb (herbaceous flowering plant).
• Grows 12-18 inches (30.5-45.7 cm) tall, sometimes reaching 1-3 feet.
• Has a deep taproot.
• Stems are branched.
• Leaves are alternate and deeply dissected or lobed. Rosette leaves also deeply lobed.
• Flowers are pinkish or purple colored.
• Bract tips are recurved.

Interactions with Other Organisms

• Seeds can be dispersed by sheep, as squarrose knapweed capitula have been found in sheep fleece.

Further Information

• USDA Agricultural Research Service Archive
• Idaho State Department of Agriculture