SafePlants

Spotted Knapweed

Spotted knapweed is a highly invasive plant species with several common names and a complex taxonomy. Understanding its characteristics and spread is crucial for effective management.

Considerations for Pets

• Spotted knapweed is described as having prickly stems.

Scientific Name and Nomenclature

• Accepted Scientific Name: Centaurea biebersteinii DC.
• Common Names: Spotted knapweed, gefleckte Flockenblume (German), gewöhnliche Rispen-Flockenblume (German).
• Synonyms and Related Species:
  • Centaurea maculosa (older, but still commonly used name)
  • Centaurea stoebe L. subsp. micranthos (Gugler) Hayek
• Family: Asteraceae (Sunflower Family)

Distribution and Habitat

• Origin: Europe and western Asia.
• Current Distribution: Widespread in the United States, particularly in the northeast and north-central regions, along the Pacific Coast, and throughout Idaho and Montana. Also found in central and eastern Oregon.
• Habitat: Invades a variety of natural habitats, including barrens, fields, forests, prairies, meadows, pastures, and rangelands. Thrives in sunny sites, especially sandy soils of low productivity, such as grasslands in Wisconsin. Also found in dry pastures and valleys facing southeast.

Ecological Role

• Invasive Species: Spotted knapweed is an exotic, perennial, and highly competitive invasive plant that quickly crowds out native grass and plant species. It replaces native vegetation and can rapidly infest large areas.
• Phytotoxic: Spotted knapweed is poisonous to other plants.
• Spread Mechanisms: Spreads quickly through artificial corridors and is dispersed by seed, which can remain dormant for up to 5 years.

Morphological Characteristics and Growth Habits

• Life Cycle: Biennial or short-lived perennial.
• Height: Can grow up to 4 feet tall.
• Roots: Possesses a strong taproot and lateral roots.
• Stems: Prickly stems.
• Flowers: Pink flowers that bloom from July through August. The flower buds are referred to as "knaps" (derived from the Anglo-Saxon word "cnaep").
• Seeds: A prolific seed producer, with each plant capable of producing up to 900 seeds annually.
• Rosette: Bolts (grows long stems) in early May from the basal rosette of leaves.

Quirky Facts

• The name "Knapweed" is derived from the Anglo-Saxon word "cnaep," meaning top, knob, or button, referring to the plant's flower bud.
• Spotted knapweed seeds can remain dormant for up to 5 years!

Interactions with Other Organisms

• Spotted knapweed is subject to biocontrol efforts, including the use of insects such as Urophora quadrifasciata.

Further Information

• Center for Invasive Species and Ecosystem Health.
• Invasive Plants : http://www.na.fs.fed.us/fhp/invasive_plants
• Tropicos