Common Knapweed - Centaurea nigra

    Alternative names
    Knapweed and as Black Knapweed
    Description

    Medium to tall hairy plant with erect stems, branched or unbranched. Thickened below the flowerhead. Flowerheads purple, 20 to 40 mm, solitary or in branched clusters, the florets all equal in length. Flower bracts with a broad, blackish triangular fringed appendage, concealing the adjacent bracts.

    Similar Species

    Greater Knapweed Centaurea scabiosa

    C. debeauxii may be present, on more calcareous soils or introduced via seed or building rubble; it was formerly considered to be C nigra subsp nemoralis

    Centaurea jacea (Brown Knapweed) has brown phyllaries and is a very rare alien species. There is only one VC55 record from Evington in 2018, but it may be introduced in wildflower mixes. Its hybrid with C. nigra (C. x gerstlaureri) has dark brown phyllaries and has not been found in  VC55.

    See the Identification Aid below for help on separating the Centaurea nigra look-alikes.

    Identification difficulty
    Identification aids

    You need to examine the phyllaries along the mid-line of the inflorescence only

    key

    Habitat

    Roadsides, flower meadows, hedgebanks and waste ground.

    When to see it

    June to September.

    Life History

    Perennial.

    UK Status

    Very common throughout Britain.

    VC55 Status

    Very common in Leicestershire and Rutland. In the 1979 Flora survey of Leicestershire it was found in 561 of the 617 tetrads.

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    Leicestershire & Rutland Map

    MAP KEY:

    Yellow squares = NBN records (all known data)
    Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

    UK Map