Centaurea cyanus (Cornflower)

Ecology

C. cyanus formerly occurred as an annual weed of arable habitats. Since 1986 it has been recorded in very few arable fields, but it is now frequent in waste places, on roadsides and on rubbish tips as a casual arising from gardens and wild-flower seed mixtures. 0-350 m (Blackwell, Derbys.).

Status

Archaeophyte

World Distribution

As an archaeophyte C. cyanus has a distribution centred on the European Temperate region; it has been widely naturalised outside this range.

© K.J. Walker, BSBI

Broad Habitats

Light (Ellenberg): 7

Moisture (Ellenberg): 5

Reaction (Ellenberg): 6

Nitrogen (Ellenberg): 5

0

Salt Tolerance (Ellenberg): 0

January Mean Temperature (Celsius): 3.8

July Mean Temperature (Celsius): 15.4

Annual Precipitation (mm): 836

Life form information

Height (cm): 80

Perennation - primary

Annual

Life Form - primary

Therophyte (annual land plant)

Woodiness

Herbaceous

Clonality - primary

Little or no vegetative spread

Distribution information

Count of 10km squares in Great Britain: 884

Count of 10km squares in Ireland: 56

Count of 10km squares in the Channel Isles: 5

Atlas Change Index: -0.39

Weighted Changed Factor: 62

Weighted Change Factor Confidence (90%)

42

Distribution information

Plantatt Conservation Status

Endangered

JNCC Designations

NBNSYS0000004503

Scarce Atlas Account

Scarce Atlas Account: 

Centaurea cyanus L.

Cornflower

Status: scarce

 

This plant was formerly a weed of arable land, particularly on sandy, rather acidic soils where it was associated with Chrysanthemum segetum. C. cyanus used to grow mainly in crops of rye, but it could occur in other spring and winter crops and as a ruderal, provided competition from other plants was slight. In the eighteenth and nineteenth centuries, it constituted a serious agricultural weed and possibly maintained its population with continuous reintroductions in rye seed from eastern Europe and Russia. Now it is more often seen as a cultivar in gardens or where ‘wild flower seed’ has been sown. 

C. cyanus is an annual. There are peaks of germination in September/October and May/June. The flowers open in long days and are self-incompatible. They are cross-pollinated by bumble bees. Fruits are relatively large and heavy and can be harvested with the grain. Although germination is greatest in the first year after sowing, viability can be retained for at least 4 years (Svensson & Wigren, 1985). This enables it to survive crop rotations as long as perennial leys are not included and the competition pressure is not too high. It occasionally overwinters.

This species has the potential to occur on suitable sites throughout Britain, and the poet John Clare referred to its "destroying beauty". The species declined rapidly with the introduction of seed screening and, later, with the advent of chemical herbicides such as 2,4-D and MCPA. This species is now known from only one persistent site in Britain, in mid-Suffolk. Isolated plants still occur over a large area of the south and east of England although these rarely persist for longer than a year. Large numbers sometimes occur when there are deep excavations for roads and pipelines. Although there are records from 127 British 10 km squares from 1970 onwards, this declining species is classified as scarce as it has been recorded in only 78 British 10 km squares from 1980 onwards.

This species is thought to have originated in southeast Europe but it has spread with agriculture and is now widespread in both the northern and southern hemispheres.

Godwin (1975) suggests that this species once grew in natural communities on scree slopes and alluvial deposits of the late-glacial tundra.

 

A. Smith

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.

Atlas text references

Atlas (291b)
The Irish Red Data Book. 1. Vascular Plants,
Curtis, T. G. F., and McGough H. N.
, Dublin, (1988)

Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols,
Hultén, E., and Fries M.
, Königstein, (1986)

Vergleichende Chorologie der zentraleuropäischen Flora. Volume 3. 2 vols,
Meusel, H., and Jäger E. J.
, Jena, (1992)

Scarce plants in Britain,
Stewart, A., Pearman D. A., and Preston C. D.
, Peterborough, (1994)

British Red Data Books. 1. Vascular plants, edn 3,
Wigginton, M. J.
, Peterborough, (1999)