A biennial herb of waste ground and tracksides in dry grassland, and on banks on well-drained sandy, gravelly or light chalky soils. Lowland.
There is a single archaeological record of this species from a Roman site, and it was recorded in the historic period by 1597. It is sometimes regarded as native in Sussex, where it grows in habitats similar to those near the Somme estuary in N. France (Wigginton, 1999). It is also established in Kent, where it has been known since 1839 at Chatham. Elsewhere it is a declining casual from wool, bird-seed, lucerne seed and esparto.
Native of the Mediterranean region; widespread as an introduction further north but now declining outside its native range.
Light (Ellenberg): 7
Moisture (Ellenberg): 4
Reaction (Ellenberg): 7
Nitrogen (Ellenberg): 3
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 4
July Mean Temperature (Celsius): 16.1
Annual Precipitation (mm): 744
Count of 10km squares in Great Britain: 153
Count of 10km squares in Ireland: 1
Count of 10km squares in the Channel Isles: 3
Atlas Change Index: -2.34
RDB Species Accounts
Centaurea calcitrapa L. (Asteraceae)
Status in Britain: VULNERABLE.
Status in Europe: Not threatened.
In Britain, C. calcitrapa is a plant of well-drained sandy, gravelly, or light chalky soils. It occurs on waste ground and tracksides, in dry grasslands and on banks, usually in broken or disturbed ground. At one time it was a plentiful, though local, weed of arable fields, though is now hardly known in this habitat, mainly because of improved seed-screening.
It is a biennial. The main flowering period is between late July and early August, but it may extend into September. The flowers are visited by bees and flies. Seed is freely produced, but dispersal is poor since the seed is heavy and falls close to the parent plant. It appears to have good viability in the seed-bank.
C. calcitrapa has declined markedly and now occurs regularly in few sites, most of which are on the South Downs in Sussex between Brighton and Eastbourne. At the present time, it appears to be established in just seven sites, five in Sussex and two in Kent. Populations are generally small, though one of the Sussex sites regularly holds several hundred plants. Elsewhere, records are generally of casual occurrences, originating mainly from wool shoddy or bird seed.
Its native status is disputed, with some authorities (e.g. Philp 1982; Stace 1991) regarding it as an introduction. Its occurrence in arable fields was dependent to a large extent on continued reintroductions as a seed impurity of lucerne from southern France or Italy. However, the fact that it was present on waste land before the introduction of lucerne around 1650 suggests that it might be native. F. Rose (in litt.) considers it to be probably native in Sussex on dry banks on the chalk, its habitats there being similar to those near the Somme estuary where also he considers it is probably native.
The two populations in Kent appeared, at least at one time, to be largely dependent on tethered or enclosed horses for maintaining open ground. At sites in Sussex, it benefits from erosion of slopes, and on tracksides from regular mowing of surrounding vegetation and trampling by cattle (FitzGerald 1988c). Seed has been dispersed by hand in at least one Sussex site.
C. calcitrapa is widespread in southern and south-central Europe (including Mediterranean islands), from Iberia eastwards to Russia and northwards to southern England, and northern France and Germany. It also occurs in North Africa, the Canary Islands, and West Asia. It seems to be in general decline in western and northern Europe, probably mainly because of agricultural intensification and the destruction of marginal habitats.
M. J. Wigginton
PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.