GREATER KNAPWEED

Centaurea scabiosa

Daisy & Dandelion Family [Asteraceae]

Flowers:
month8jul month8july month8aug month8sep month8sept

Pappus: pappusZpossible (short)
pappus8sep pappus8sept pappus8oct

status
statusZnative
flower
flower8purple
inner
inner8black
morph
morph8actino
petals
petalsZMany
stem
stem8angular
stem
stem8ribbed

28th June 2011, Hightown, Sefton Coast. Photo: © RWD
Grows up to 4 feet tall, with branched rough stiff stems and rayed purple flowers.


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
It is a dark-green plant rather than the greyish-green of the similar Common Knapweed which can also have flowers of the rayed form. Un-like Common Knapweed the stem leaves are narrow with narrow side-lobes.


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
Exists in rayed form only. Un-like Lesser Knapweed (now known as Chalk Knapweed (Centaurea debeauxii)) which has similarly coloured leaves, the head (actually the 'un-opened' flower bud) beneath the flower is spherical rather than Greek urn-shaped.


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
Like rayed versions of Common Knapweed but un-like Lesser Knapweed, the stems are swollen immediately below the dark spherical flower-bud.


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
All Knapweeds consist entirely of disc florets; the long ray-like flowers on the outer edge of rayed versions are actually sterile and deeply cleft disc florets, cut into five strands.


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
Inner disc florets are a deeper purple, with white tips (these are fertile disc florets)


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
A Five-spot Burnet Moth atop.


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
Bird's-eye view.


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
The bare spherical flower buds with deeply toothed brown to blackish 'phyllaries' and areas in-between looking like dark-green shields.


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
Lower stem leaves longer and with more narrow lobes. Stems rough with hairs.


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
Stems angled.


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
Upper stem leaves shorter and with fewer lobes.


28th June 2011, Hightown, Sefton Coast. Photo: © RWD
Stems angled in places, with reddish-brown ridges on the edges.


Not to be semantically confused with: Common Centaury (Centaurium erythraea) nor with similar Centauries such as Seaside Centaury (Centaurium littorale) [plants whose scientific names are similar, but which are in a totally different Family altogether, the Gentian Family (Gentianaceae)].

Easily confused with : rayed versions of Common Knapweed but especially of Lesser Knapweed (now known as Chalk Knapweed (Centaurea debeauxii)).

Easily mis-identified as : a rayed version of Lesser Knapweed(now known as Chalk Knapweed (Centaurea debeauxii)) but that has a Greek urn shaped 'head' or flower bud and leaves that have far fewer lobes, but rather with two auricles going part-way around each side of the stem.

Hybridizes with : Brown Knapweed (Centaurea jacea) which is almost extinct in the UK to produce Hybrid Knapweed (Centaurea × gerstlaueri) which seems to be available as a garden plant, so is slightly more widespread.

Not to be confused semantically with : Knotgrasses such as Knotgrass, Cornfield Knotgrass, Equal-leaved Knotgrass or Northern Knotgrass which belong to the Dock & Knotweed Family, namely Polygonium [they both have similar names]. Nor should they be confused with Knotweeds such as Giant Knotweed, Japanese Knotweed or Lesser Knotweed which also belong to the Dock & Knotweed Family (Polygonium).

The Centaurea Genus encompasses many plants with thistle-like flowers (but not thistle-like stems or leaves), many of which have 'rays' on the outer edge which consist not of ray-florets (flat 'petals') but very long tubular disc-florets that have five deep clefts at the end, much like as those in Greater Knspweed, although not all are purple. Besides the Knapweeds, these include such plants as the sky-blue Cornflower, Perennial Cornflower and others that are not rayed such as Red Star-Thistle, Yellow Star-thistle and Lesser Star-thistle. Mr Clive Stace thinks the genus over-crowded with disparate plants, and that this genus is ripe for splitting into other genera.

Grows in grassy places especially on lime. Sometimes it is host to a parasitic plant called Knapweed Broomrape (Orobanche elatior) which specialises in being parasitic only on Greater Knapweed which may be several metres away, but connected underground.


  Centaurea scabiosa  ⇐ Global Aspect ⇒ Asteraceae  

Distribution
 family8Daisy & Dandelion family8Asteraceae

 BSBI maps
genus8Centaurea
Centaurea
(Knapweeds)

GREATER KNAPWEED

Centaurea scabiosa

Daisy & Dandelion Family [Asteraceae]

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