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Meadow knapweed

Quick facts

Meadow knapweed is an invasive species.

  • Meadow knapweed grows best in sunny, wet conditions, such as roadsides, riparian areas and wet meadows.
  • It can outcompete native vegetation, resulting in habitat loss.
  • This plant can hybridize with other knapweeds, allowing for aggressive dispersal.

Meadow knapweed should be reported. The Minnesota Department of Natural Resources provides detailed recommendations for reporting invasive species.

stem of meadow knapweed growing in the grass

How to identify meadow knapweed

  • Perennial plant, one to three and one half feet tall.

Stem

  • Multiple long, upright, branching stems with solitary flower heads at the apexes.
  • Stems are thin, green to reddish, have long ridges running vertically and have a cobweb-like appearance.

Leaves

  • Lance-shaped leaves with short fuzzy hairs.
  • Basal leaves can grow up to four inches long and point upward.
  • The lower leaves are toothed or lobed and the upper leaves are linear.
  • Leaves get smaller as they ascend the plant.
  • Leaves can be variable, having no lobes, one lobe or many lobes.
  • Upper leaves rarely have lobes.

Flowers

  • Light pink to purple, about three fourths of an inch diameter.
  • Each flower head is a cluster of small flowers but appears as a single flower.
  • Flower heads are more rounded than other knapweeds and have a spiderweb appearance.
  • Flower heads can be slender, egg shaped, stout or round.
  • Bracts can have short to long fringes at the tips and tan to blackish coloring on bract bases.
  • When flowering, the bracts give off a metallic golden sheen.
  • Blooms July to August.

Seeds

  • White to light brown.
  • Sometimes have short hairs on the opposite point of attachment.

Roots

  • Seedlings have a taproot, with mature plants forming clustered roots below the woody crown.
    purple meadow knapweed flower
    Meadow knapweed
side view of the purple meadow knapweed flower
Meadow knapweed

 

Angela Gupta, Extension educator; Amy Rager, Extension educator; Megan M. Weber, Extension educator

Reviewed in 2019

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