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The Status of Centaurea cyanus in Britain
DRAFT
P. J. Wilson
February 2007
ISBN 1 90479-80-1

DRAFT
Plantlife wishes to acknowledge the financial support of the Back from the Brink
programme and Arable Plants Project from Natural England, the Esmée Fairbairn
Foundation and supporting charitable trusts and members.
The cover illustration is reproduced by kind permission of Midsummer Books Ltd from ‘The Wild Flowers of the
British Isles’ by Ian Garrard and David Streeter, © Midsummer Books Ltd
2

Summary
DRAFT
Centaurea cyanus (cornflower) is an attractive and charismatic species of arable land throughout
Europe. In Britain however it has become extremely rare in recent years and is listed as a priority
species in the UK Biodiversity Action Plan. Its true distribution as a naturally-occurring species in
Britain has however been obscured by widespread introductions and colonisation from introduced
populations. Naturally occurring arable sites are therefore difficult to distinguish, and this has lead to it
being classified as a species of ‘Least Concern’ in the recent Red Data Book of vascular plants.
British records of Centaurea cyanus were reviewed with the help of Botanical Society of the British
Isles vice-county recorders, in an attempt to determine which were of natural occurrence and which
were recent introductions or of other non-natural origin.
Of the original 369 sites in 240 10km squares, only 105 sites in 81 10km squares were thought to be
naturally occurring. The suspected natural sites therefore represent only 29% of the total number
recorded and the number of 10km squares are only 34% of the total number.
Notable concentrations of records are found in the coastal strip of South Devon, the south-west of the
Isle of Wight, south-central Suffolk, the area around St Albans, and north of the Cromarty and Beauly
Firths in north-east Scotland.
Note. In this report, the terms “natural” and “naturally occurring” are used to refer to populations of
Centaurea cyanus that have not originated by deliberate planting or by secondary colonisation from
deliberately planted populations. In the case of an archaeophyte species such as C. cyanus (sensu
Preston et al, 2004), where the original distribution of a species is uncertain, terms such as “native”
have no true meaning.
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Contents
DRAFT
Page Number
5 Introduction
7 Methods
8 Results
10 Discussion
11 Acknowledgments
12 References
13 Appendix
4

Introduction
DRAFT
Anecdotal evidence suggests that Centaurea cyanus is a species in rapid and catastrophic decline in
Britain, yet the published data shows no long-term decline, with 264 10km square records from 1930-
1960 (Perring & Walters, 1960) and 396 between 1987 and 1999, and a change index of only –0.39
(Preston et al, 2002).
The decline of this species was noticed as early as the beginning of the 20 th century in several local
floras. The following example is typical: White (1912) described it as rare in the Bristol area and went
on to say “I remember as a boy gathering bunches of its flowers in the great expanse of cornfields that
then enveloped the town of Dorchester on the south and west……….in the last edition of the Dorset
Flora I find no mention of the blue-bottle in all that area”. The late 19 th -century flora (Mansell-
Playdell, 1895) recorded it in six places in Dorset, but Bowen (2000) recorded it in 24 2kmX2km
squares.
Declines in the late 19 th century and early 20 th century were due to the improvements in methods of
seed cleaning associated with the introduction of efficient threshing machinery and standards for
quantities of seed contaminants (Wilson & King, 2003). The link between seed-cleaning and the
decline of C. cyanus and several other species has been well-documented in central Europe (Kornas,
1986, 1988). It is likely that further declines in the early 20 th century were due to the reduction in the
area of land under arable cultivation during a period of agricultural depression. There is some evidence
of a small recovery in the 1940s following the cultivation of grassland in response to the need for
increased arable production during and after the Second World War. This recovery was however shortlived,
and along with many other species of arable plant, numbers of sites for C. cyanus declined
further with the introduction of herbicides for weed control and highly competitive crop varieties and
other processes of intensification in the 1950s (Wilson, 1990). In a survey of more than 300 fields in
England including those of the greatest importance for arable plant conservation carried out between
1987 and 1990, no sites for C. cyanus were recorded (Wilson, 1990), neither were any sites recorded in
the BSBI/NCC survey of 1986-87 (Smith, 1988). This decline led to the inclusion of C. cyanus on the
priority list of the UK Biodiversity Action Plan (Anon, 1997).
Much of the apparent increase in numbers of populations in recent years is thought to have been due to
the widespread use of this species in ornamental and amenity plantings, for instance on the verges of
newly constructed roads, urban landscaping and even in arable fields, and also following secondary
colonisation from gardens and other deliberate plantings. At the same time however, the
implementation of arable extensification measures in Britain has meant that C. cyanus of apparently
natural provenance has appeared in several sites where its previous existence was not suspected
It can be difficult to distinguish between natural and introduced populations of C. cyanus, and as a
result of this, the distribution of C. cyanus as a naturally occurring plant has been obscured. In the
recently produced red data list of British vascular plants (Cheffings & Farrell, 2005), it was classified
as of “Least Concern”, the lowest conservation priority, because it was impossible to separate casual
sites from those at which it was of natural occurrence and all were treated equally. This has led to
concerns that C. cyanus may be dropped as a Priority Species for conservation action in future reviews
of the UK Biodiversity Action Plan, because of lack of information about its true distribution as a
naturally occurring plant in the country.
5

DRAFT
There is a clear need to distinguish between populations of C. cyanus that exist as ancient components
of arable communities and those of a more recent, non-arable origin, and a clarification of the status of
C. cyanus is clearly desirable if this charismatic species is not to lose its position as a flagship for plant
conservation in arable fields.
6

Methods
DRAFT
A listing of all British records for Centaurea cyanus since 1980 from the Biological Records Centre
was ordered by Watsonian vice-county and duplicate records were eliminated. The relevant records
were then sent to Botanical Society of the British Isles (BSBI) vice-county recorders for their
comments and for them to add any further sites. BSBI recorders are experts on their regional floras,
often with many years of experience and unrivalled knowledge of their county, and are frequently have
much information about the localities for rare species and about the overall status of these, information
that is not otherwise available to the public.
Information from the BSBI recorders and other experts was then fed back into the records database,
and used to eliminate all sites that were obvious or highly likely introductions or of secondary origin
from introduced populations. This sieving of records was carried out with caution, and wherever any
doubt remained about the status of a population, it was assumed to be natural. By using this
conservative method, the danger of discarding potentially natural sites and any tendency to overstate
the rate of decline of C. cyanus were minimised.
The result of this process was a list of sites at which C. cyanus could be considered to have been
naturally occurring between 1987 (the start of the Atlas recording period) and 2005. This included
well-established arable sites where C. cyanus was of regular occurrence, arable sites where it was only
recorded on a few occasions, and non-arable sites where the seed could conceivably have originated
from natural sources.
7

Results
DRAFT
Requests for information were sent to 54 BSBI vice-county recorders. Returns were received from 49
of these.
Records were collected from 369 sites in 240 10km squares in 49 English, Welsh and Scottish vicecounties.
These records were from the Biological Records Centre and from BSBI recorders, and
included naturally occurring sites, casual records of unknown provenance and suspected introductions.
After data sieving, these reduced to 105 sites in 81 10km squares (Table 1). The suspected native sites
are therefore only 29% of the total number recorded and the number of 10km squares are only 34% of
the total number. If these proportions are applied to the 396 10km squares mapped in the Atlas, these
are reduced to 135 in which C. cyanus is likely to be have been naturally occurring between 1987 and
1999.
There are some notable concentrations of records. These include the coastal strip to the south of
Dartmouth in South Devon, the south-west of the Isle of Wight, south-central Suffolk, the area around
St Albans, and north of the Cromarty and Beauly Firths in north-east Scotland.
Table 1. Numbers of 10km squares and sites in Britain in which Centaurea cyanus is considered to
have occurred naturally between 1987 and 2005.
Vice-county Number of 10km squares Number of sites
West Cornwall 2 2
South Devon 7 12
South Somerset 2 3
North Somerset 1 1
North Wiltshire 2 2
South Wiltshire 1 1
Dorset 3 3
Isle of Wight 3 5
West Sussex 4 5
Surrey 2 3
South Essex 2 2
Hertfordshire 6 9
Oxfordshire 5 6
Buckinghamshire 1 1
Suffolk (East and West) 9 10
Cambridgeshire 5 5
Northamptonshire 1 1
East Gloucestershire 3 4
Worcestershire 3 3
Warwickshire 1 1
Shropshire 2 2
Pembrokeshire 3 3
North Lincolnshire 4 4
South-east Yorkshire 2 3
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DRAFT
Berwickshire 1 1
Morayshire 2 2
East Ross 4 11
81 105
Fig 1. The distribution of sites in Britain, in which Centaurea cyanus is considered to have occurred
naturally between 1987 and 2005.
9

Discussion
DRAFT
The use of expert local knowledge has proven effective in eliminating suspected introduced or casual
populations of Centaurea cyanus from the listed records. Approximately 71% of records are thought to
be of non-natural occurrence. The following comments from BSBI recorders are typical: “all recent
records are introductions or seed contaminants and none have persisted for more than a year or two”
(RD Pryce, Carmarthenshire), “all recent records are casual, all results of wild-flower seed sowing” (C
Boon, Bedfordshire), “we are convinced that these and all other more recent sites are only of a casual
nature, either as deliberate introductions or constituents of seed mixes” (J Hawksford, Staffordshire).
Although information on population sizes and frequency of occurrence was not requested from BSBI
recorders, comments suggest that very few populations are large or recorded regularly, and this further
emphasises the high conservation needs of this species. There are probably fewer than 30 sites that can
at present be considered as having regular “good” populations of C. cyanus, although this may increase
as more sites are brought into sympathetic management under stewardship agreements aimed at the
conservation of this species.
There is some tendency for aggregation of sites within areas of the country. Some of these are
mentioned above. It is possible that further searching of arable fields in these areas may reveal
additional sites, and it is recommended that C. cyanus should be a target species for appropriate
management under Entry Level Stewardship, Higher Level Stewardship or the relevant Scottish or
Welsh schemes in these areas.
A careful study of records with the benefit of expert local knowledge can help distinguish naturallyoccurring
populations of C. cyanus from those originating from deliberate and non-deliberate
introduction. The status of populations that appear on disturbed ground without any obvious nonnatural
origin is more difficult to assess. In some cases these may originate from buried seed on former
arable sites, brought to the surface by for example road construction or pipeline digging. In other
situations the seed may derive from non-natural sources. In either case, it is highly unlikely that any
population will persist in such habitats liable to very rapid successional changes, and such populations
act in the same way as other casual populations appearing in small numbers and rarely persisting for
more than a single year.
It seems likely therefore that the decline in numbers of 10km squares occupied by naturally-occurring
populations of C. cyanus in Britain has been underestimated, and that with careful examination it is
possible to make a more accurate estimate of this species’ natural status. The IUCN category assigned
to this species in the Red Data List (Cheffings & Farrell, 2005) should be re-assessed in the light of
these findings.
10

Acknowledgements.
DRAFT
Many thanks are due to all of the BSBI recorders who contributed their expertise: Colin French, Roger
Smith, Paul Green, Ian Green, Sharon Pilkington, David Pearman, Colin Pope, Mary Briggs, Paul
Harmes, Ann Sankey, Ken Adams, Trevor James, Mick Crawley, John Killick, Roy Maycock, Martin
Sanford, Nick Millar, Chris Boon, Gillian Gent, Mark and Clare Kitchen, Stephanie Thompson, John
Partridge, John Day, John Hawksford, Sarah Whild, Richard Pryce, Stephen Evans, Arthur Chater, Paul
Benoit, Malcolm Pool, Paul Kirby, David Wood, Dave Earl, Richard Middleton, Phyl Abbott, GA
Swan, Geoffrey Halliday, Michael Braithwaite, GH Ballantyne, Neale Taylor, Edna Stewart, Barbara
Ballinger. Other information provided by The Northmoor Trust, Mike Ingram, Dick Potts, Kevin
Walker, Trevor Dines, Andy Byfield, Kate Still and Deborah Long.
11

References
DRAFT
Anon (1998). UK Biodiversity group, Tranche 2 Action Plans; Volume 1 vertebrates and vascular
plants. English Nature, Peterborough.
Bevis JH, Kettell RE & Shepard B (1978). Flora of the Isle of Wight. Yelf, Newport.
Bowen H (2000). The Flora of Dorset. Pisces Publications.
Cheffings CM & Farrell L (2005). Species Status No. 7, The Vascular Plant Red Data List for Great
Britain. JNCC, Peterborough.
Good RD (1948). A Geographical Handbook of the Dorset Flora. Dorset County Museum.
Grose D (1957). The Flora of Wiltshire. WANHS, Devizes.
Kay S & Gregory S (1999). Rare Arable Flora Survey 1999. Northmoor Trust, Little Wittenham.
Margetts LJ & David RW (1981). A Review of the Cornish Flora. Institute of Cornish Studies,
Redruth.
Martin WK & Fraser GT (1939). Flora of Devon. Buncle, Arbroath.
Kornas J (1988). Speirochore ackerwildkrauter: von okologischer spezialisierung zum aussterben.
Flora 180, 83-91.
Lousley JE (1976). Flora of Surrey. David & Charles, Newton Abbot.
Mansell-Pleydell JC (1895). The Flora of Dorsetshire. Privately printed, Dorchester.
Perring FH & Walters SM (1962). The Atlas of the British Flora. Nelson, London.
Preston CD, Pearman DA & Dines TD (2002). New Atlas of the British and Irish Flora. Oxford
University Press.
Roe RGB (1981). The Flora of Somerset. Bigwood & Staple, Bridgewater.
Smith A (1987). Endangered Species of Disturbed Habitats. Nature Conservancy Council,
Peterborough.
Townsend F (1904). Flora of Hampshire. Lowell, Reeve, London.
White JW (1912). The Flora of Bristol. Chatford House, Bristol.
Wilson PJ (1990). The Ecology and Conservation of Rare Arable Weed Species and Communities.
University of Southampton.
Wilson PJ (2002). Cridmore Farm Arable Fields. Management for the Conservation of the Arable
Flora.
Wilson PJ & King M (2003). Arable Plants, A Field Guide. Wild Guides.
Wolley-Dod AH (1937). Flora of Sussex. Chatford House, Bristol.
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DRAFT
Appendix 1. Status of Centaurea cyanus in Britain by county.
Cornwall
Never a common species in Cornwall, and described by Margetts & David (1980) as “always rare in
Cornwall and now only casual”, Centaurea cyanus has been recorded recently in two Cornish
localities. There have been relatively few recorded instances of this species occurring as a casual or an
introduction in the county, although some records have been attributed to the use of “wildflower seed”.
There are two undoubted arable records in recent years, one on the Lizard and one near Falmouth.
Devon
Described in 1939 (Martin & Fraser, 1939) as “becoming rare” and “an escape from gardens in many
of its locations”, records were then scattered throughout the county. Its decline then was associated
with the agricultural depression of the early part of the 20 th century. In recent years, the area around
Dartmouth has emerged as a stronghold of this species, having been recorded in several fields owned
by the National Trust around the Dart Estuary. Some of these fields are now managed for their rich
arable flora. Other sites are more typical, with a few plants present in fields to the north of Exeter,
north of Plymouth and Bridford, while numerous plants were recorded from a field near Torquay.
Several of these isolated fields were recorded by RSPB. It is possible that further sites remain to be
discovered, particularly in the South Hams area.
There are no recent records from central and north Devon.
Somerset
Said by Roe (1981) to have been “rare by the end of the 19 th century and only recorded a few times
since”. Centaurea cyanus had almost disappeared from Somerset by the early years of the 20 th century,
probably as a result of the agricultural depression of this period (White,1912) The great majority of
recent records are casual and resulting from deliberate introductions. There are however two probable
records of naturally occurring populations in arable fields, one from near Taunton and the other near
Frome.
Wiltshire
Grose (1957) gives a concise account of the status of this species in Wiltshire since the mid-19 th
century. In 1845 it was common in cornfields, and was still widely distributed in 1867. By the end of
the 19 th century with the decrease in area of arable land it had become very rare, but when large areas
of grassland were returned to arable cultivation during the second world war, Centaurea cyanus
reappeared in large quantities. By 1957 it had “diminished again now and is rarely seen”. In the
1940s, the majority of records were from the Marlborough area, and the two sites currently known in
North Wiltshire are from the same area. Both of these sites are on greensand, and there are other
nearby localities at which C. cyanus may reappear. At the site near Shalbourne it is of erratic
appearance in fields which also have populations of Ranunculus arvensis and Myosurus minimus. At
13

DRAFT
the Pewsey site regular small numbers occur in field margins managed under the Countryside
Stewardship Scheme.
A single arable site has recently been reported on the chalk to the south of Salisbury Plain. Centaurea
cyanus also occurs in field margins on a farm at Cholderton, but here it is thought to have been
introduced.
Dorset
Centaurea cyanus has not been a common species in Dorset since the mid-19 th century. There are only
six records in Mansell-Pleydell (1895), and Ronald Good recorded it in only a single arable stand in the
1930s (Good, 1938). It was recorded in 12 localities between 1987 and 2005, but at only three of these
was it thought to be possibly of natural occurrence, and in only two was it present in arable land. Both
of these sites were on chalk to the west of Blandford, and one of these at Milborne St Andrew was
where Good saw it in the 1930s.
Isle of Wight
The declines of Centuarea cyanus on the Isle of Wight parallel those in other counties. It
was recorded as common on the Isle of Wight in the mid-19 th century (Bromfield 1856), and individual
records were not listed. By 1904, only four localities were known, and Bevis et al (1978) describe
“only isolated single records”, although at one of these at East Medina it was abundant in 1963.
Cridmore Farm near Godshill has been a well-known site for C. cyanus since the early 1990s (Wilson,
200. In some years it occurs abundantly in several fields here with other species including Valerianella
rimosa, Silene gallica and abundant Chrysanthemum segetum. Field margins are managed under the
Countryside Stewardship Scheme. Four other small populations have been recorded in recent years
from the south-west of the island.
Sussex
“Formerly frequent and locally plentiful, now becoming rare” (Wolley-Dod, 1937). At the beginning
of the 20 th century there were few recorded sites. In recent years Centaurea cyanus was recorded in
small numbers in five localities in the west of the county. In 1999 C. cyanus was first recorded from
field margins managed under the Countryside Stewardship Scheme in the Game Conservancy Trust’s
study area on the South Downs, and had become common on one farm by 2005. It was considered
possible that the plants had originated in imported linseed seed.
Surrey
Never considered as common in Surrey as elsewhere, it was very rare by the 1970s (Lousley, 1976).
Several sites were recorded between 1946 and 2005, but it was considered to be naturally occurring in
very few of these, and was persistent in even fewer. It was present in abundance in three arable fields
near Egham between 1965 and 1972, but could not be refound in the 1990s. In recent years it has been
found in three sites between Farnham and Guildford.
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DRAFT
Essex
There are very few recent records for Centaurea cyanus from Essex. Small populations were recorded
near Margaretting and Dunmow.
Hertfordshire
Centaurea cyanus has been recorded from several sites in Hertfordshire in recent years. The majority
of these have been known or suspected introductions. There are however some that are thought to be
of natural origin, and there is a cluster of these between Berkhamsted, Potters Bar and Baldock. These
include a field managed under the Countryside Stewardship Scheme near London Colney, where it can
be seen from the adjacent M25, and seed from here has been sown on an adjacent reserve owned by the
Hertfordshire and Middlesex Wildlife Trust. Centaurea cyanus is also regularly seen in the margin of a
field used as one of the classic experiments at the Rothamsted Experimental Station.
Oxfordshire
The only sites at which Centaurea cyanus has been recorded as of possible natural occurrence in
Oxfordshire are at Tubney Manor Farm and Pishill. These sites were discovered by The Northmoor
Trust during their field by field surveys of parts of the county (Kay & Gregory, 1999). The first is on
the Jurassic sand to the west of Abingdon, in a species-rich field that also had Apera interrupta,
Scandix pecten-veneris and Chrysanthemum segetum. The two fields at Pishill are on the chalk of the
Chilterns near Henley on Thames. There are several known introductions in Oxfordshire, including
Radcot Farm where industrial quantities of arable plant seed have been sown.
Buckinghamshire
Several suspected introductions of Centaurea cyanus have been recorded from Buckinghamshire, but
only a single population at Emberton Island Field was thought to be naturally occurring, where a single
plant was recorded in 1987.
Suffolk
Centaurea cyanus has been recorded from 35 sites in Suffolk since 1987. As might be expected, the
majority of these are known or suspected introductions, however Suffolk appears to have more possibly
naturally occurring sites than any other British county. Eleven possibly natural sites have been
recorded since 1987, largely from the eastern part of the county. These include the Haughley site,
which for some years was thought to be one of very few localities in the country. This margins of this
field are managed under the Countryside Stewardship Scheme. In 1987 Centaurea cyanus and several
other rare arable species were introduced deliberately to several fields in the county by the Suffolk
Wildlife Trust, but it did not persist at any of these.
15

Cambridgeshire
DRAFT
Recorded from a number of sites in Cambridgeshire in recent years, but the majority of these are
known or suspected introductions. Five probably natural sites are known, three of which are near
Cambridge itself.
Northamptonshire
There is only a single known site for Centaurea cyanus from Northamptonshire. It appears to be of
natural occurrence there.
Gloucestershire
Centaurea cyanus has been recorded in few sites in Gloucestershire in recent years. These however
include a site in the Cotswolds where it is present in two fields managed under an ESA agreement for
arable plants. It is thought to be of natural occurrence at two other sites.
Worcestershire
There are numerous records for C. cyanus from Worcestershire as a casual or a known introduction
since 1987. The majority of these are on road verges. There are only four records that are thought to
be natural occurences, three of which were of single plants and the fourth was of only 3-4 plants.
Warwickshire
Centaurea cyanus has been recorded from several sites as a casual in recent years, but is also seen
regularly in a single arable field.
Shropshire
Centaurea cyanus is thought to occur naturally at two sites to the north-west of Shrewsbury.
Pembrokeshire
The only possibly natural sites for Centaurea cyanus in Wales are now thought to be in Pembrokeshire.
Although the majority of records are obvious casuals or introductions, there are nevertheless three sites
at which it is likely to occur naturally. At two of these, plants were seen in single years only. At the
third, near Pembroke, it was frequent in an organic wheat crop in 2003.
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Lincolnshire
DRAFT
Centaurea cyanus has been recorded as an introduction or casual from several sites in Lincolnshire.
There are however four sites at which it may be of natural origin. These are scattered across the south
of the county, and in one of these near Gainsborough it was abundant in six acres of a field of wheat in
1999.
Yorkshire
The only recent records for Centaurea cyanus as probably naturally occurring in Yorkshire are from a
small area to the north-east of Beverley.
Berwickshire
The only site known from the Scottish borders in recent years was in 1998 near Duns, in set-aside and
turnips.
Morayshire
Centaurea cyanus is known as a casual and introduction on road verges and waste ground in this area.
It has also however been recorded as possibly natural in two arable fields. At one site near Elgin it is
recorded annually.
East Ross
This county appears to be one of the major strongholds for Centaurea cyanus in Britain. Several sites
are known where it has been recorded in recent years in arable land and where it is thought to be of
natural origin. These are clustered around the head of the Beauly Firth and to the north of the Cromarty
Firth, probably reflecting the limited distribution of arable land in this predominantly upland county.
17