Common Knapweed - Centaurea jacea

Scientific Name: Centaurea jacea (Asteraceae). There is a plethora of synonyms, varieties and subspecies, and considerable taxonomic confusion and argument about this species. Includes C. nigra and C. jacea subsp nigra.

English Name: Common Knapweed, Lesser Knapweed, Brown-rayed Knapweed, Black Knapweed, Slender Knapweed, Hardhead.

French Name: la Centaurée noire.

C. jacea (probably not subsp nigra)

5 Key Characters:
  • very variable!
  • leaves usually lanceolate.
  • pinky-purple flowers may or may not have long marginal florets, depending on variety or subspecies.
  • plant roughly hairy and tough stemmed.
  • the various varieties and subspecies mainly identified by examination of the involucural (flower head) bracts -- a dark art to which very few botanists will commit themselves.

Lookalikes: Greater Knapweed C. scabiosa, which has deeply divided leaves and different involucural bracts.

Habitat: Grasslands, roadsides, waste ground, meadows, thickets and shady places.

Flowering Period: June-July-August-September.

Status: Very common. The most widespread here is C. jacea subsp nigra, which rarely has a 'crown' of long marginal florets.

Photographed by Loire Valley Nature:

No comments:

Post a Comment