71.) ECHINOPS to CARTHAMUS

ASTERACEAE - Daisy family

Subfamily CARDUOIDEAE

Tribe CYNAREAE

ECHINOPS L.

Echinops sphaerocephalus L. (ssp. sphaerocephalus) (Glandular Globe-thistle) / General

CARLINA L.

Carlina vulgaris L. (ssp. vulgaris) (Carline Thistle) /- Grassland Scarce Restricted to skeletal limestone slopes with short open turf and scree. It has declined, likely due to loss of its required open habitat to scrub encroachment.

ARCTIUM L.

Arctium lappa L. (ssp. lappa) (Greater Burdock) / General Found along river banks, roadsides.
Arctium lappa x A. minus = A. x *nothum* (Ruhmer) J. Weiss (Greater x Lesser Burdock) - 1 record General
Arctium tomentosum Mill. (Woolly Burdock) - 1 record General
Arctium minus (Hill) Bernh. (Lesser Burdock) / General Found in a wide array of habitats but has a strong preference for woodland borders and the edges of fields under trees.
ssp. minus General The nominate plant with the same range and distribution as the species.
ssp. pubens (Bab.) P. Fourn. (Lesser Burdock) General Scarce Widely scattered over the region but greatly overlooked. It differs from the nominate plant in having slightly larger more rounded and pubescent cobweb-like capitula.
Arctium nemorosum Lej. (Wood Burdock) General

[All records are probably errors.]

CARDUUS L.

Carduus tenuiflorus Curtis (ssp. tenuiflorus) (Slender Thistle) - Coasts
Carduus pycnocephalus L. (ssp. pycnocephalus) (Plymouth Thistle) General Extinct A native of southern Europe; recorded at Bedminster in 1930 and Avonmouth Docks in 1931 by C.I. Sandwith; there again in 1935 by ?; and at Ashton Gate in 1937 by ?.
Carduus crispus L. ssp. multiflorus (Gaudin) Gremli (Welted Thistle) / General
Carduus crispus x C. nutans = C. x *stangii H. Buek ex Nyman (nothossp. stangii*) (Welted x Musk Thistle) Grassland
Carduus nigrescens Vill. ssp. vivariensis (Jord.) Bonnier & Layens (Blackening Thistle - NATURESCENE - Flowers of the Cévennes) - waste ground by Mangotsfield Station in 1896 - tracked down by Mr. S. T. Dunn after detecting it at Bath Flower Show in 1896. - Brist. Fl. General
Carduus acanthoides L. (ssp. acanthoides) (Broad-winged Thistle) - 2 BSBI records (also on NBN) General
Carduus acanthoides x C. nutans = C. x *orthocephalus* Wallr. (Broad-winged x Musk Thistle) - Sandwith (1932) General Extinct Recorded at Avonmouth Docks in 1932 by C.I. Sandwith. This appears to be the only record of its kind in the British Isles.
Carduus nutans L. (ssp. nutans) (Musk Thistle) / Grassland A white form was found near Corston, Bath in 2026 by R. Messer.

[Carline Thistle - white form found near Corston, Bath in 2026 by Robert Messer Facebook]

Carduus macrocephalus Desf. (Giant Thistle) - (Sandwith, 1932 [as C. nutans var. macrocephalus]) General Extinct A native of the Mediterranean; recorded at St Philip's Marsh in 1916 by M. Cobbe and G.C. Druce; and at Avonmouth Docks in 1931 and 1932 by C.I. Sandwith; and there again in 1938 by ? [BMAG].

CIRSIUM Mill.

Cirsium eriophorum (L.) Scop. (Woolly Thistle) / Grassland Found in limestone grassland.
Cirsium vulgare (Savi) Ten. (ssp. vulgare) (Spear Thistle) / General Very Common Abundant in a range of grassy and disturbed places though only ever plentiful following recent soil disturbance.
Cirsium dissectum (L.) Hill (Meadow Thistle) / Wetland Restricted to wet meadows. Formerly more widespread.
Cirsium erisithales (Jacq.) Scop. (Yellow Thistle) General Found as an escape in Nightingale Valley, Leigh Woods in the 1980s, first detected by C.M. Lovatt.
Cirsium acaule Scop. (ssp. acaulon) (Dwarf Thistle) /- Grassland - [bizarrely Kew has it as C. acaulon] A component of short species-rich calcareous grassland. It has declined.
Cirsium acaule x C. palustre = C. x *kirschlegeri* Sch. Bip. (Stace, NBN) (Dwarf x Marsh Thistle) 1914 Grassland
Cirsium palustre (L.) Scop. (Marsh Thistle) / Wetland Found in wet grassland, heaths and damp woodland rides.
Cirsium arvense (L.) Scop. (Creeping Thistle) / General
var. arvense General
var. incanum (Fisch.) Ledeb. - Brist. Fl., Glos. Fl. General

NOTOBASIS (Cass.) Cass.

Notobasis syriaca (Syrian Thistle) - Glos. Fl. General Extinct A native of the Mediterranean; recorded at Ashton Gate in 1937 by C.I. Sandwith.

ONOPORDUM L.

Onopordum acanthium L. (ssp. acanthium) (Cotton Thistle) /- General Very Rare var. viride was recorded on waste ground near the deserted Avonside brick-works at St Philip's, 1903-9; Portishead Station-yard, 1905, Miss Livett in White Fl. but is no longer recognised today.

"The specimens found on city rubbish at St. Philip's, and on the mill refuse at Portishead, are obviously introductions. They differ...in some respects; being taller, less branched, greener, and less cottony." (White, 1912).

Onopordum illyricum L. (ssp. illyricum) (Illyrian Thistle) - Sandwith (1932) General Extinct A native of the Mediterranean; recorded at St Philip's Marsh in 1921 by I.M. Roper - a first and only record for the British Isles.

CYNARA L.

Cynara cardunculus L. (ssp. cardunculus) (Globe Artichoke) / General Widely cultivated both for food and ornamental statement. Sometimes escapes.
var. cardunculus (Cardoon) General Found at the base of a wall on Filton Ave in 2023 by D. Peters.
var. scolymus (L.) Fiori) (Globe Artichoke) General Grown for eating.

SILYBUM Adans.

Silybum marianum (L.) Gaertn. (Milk Thistle) General Very Rare A rare introduction of roadsides and other disturbed places. First recorded in our region at Horfield in 1878 by W.E. Green.

SERRATULA L.

Serratula tinctoria L. (ssp. tinctoria) (Saw-wort) /- General Scarce A localised species of species-rich grassland, usually on damp soils.

MANTISALCA Cass.

Mantisalca salmantica (L.) Briq. & Cavill. (Dagger Flower) 1922 General Extinct A native of the Mediterranean; recorded at Baptist Mills in 1911 by I.M. Roper; St Philip's Marsh and Eastville in 1916 by M. Cobbe; Ashton Gate in 1918 and Bedminster in 1922 by C.I. Sandwith (as C. salmantica) [BMAG].

CENTAUREA L.

Centaurea scabiosa L. (ssp. scabiosa) (Greater Knapweed) / Grassland Uncommon Found in species-rish calcareous grassland, cliff tops, rock faces, railway sidings and roadsides. A white form has long been known on St Vincent's Rocks. Most concentrated along the eastern edge of the region.
var. scabiosa Grassland The nominate plant with the same range and distribution as the species.
var. succisifolia E.S. Marshall Grassland With almost entire leaves.

[Record was sent to BRERC but I can't find it.]

Centaurea stoebe L. ssp. stoebe (Spotted Knapweed) - [Sandwith, 1932 (as C. maculosa)] - 2 records (on DB as C. maculosa) General Extinct - place before C. cineraria? A native of continental Europe; recorded at Avonmouth Docks in 1930 by C.I. Sandwith (as C. maculosa).
Centaurea cineraria L. (which sspp.? - ssp. cineraria?) (Silver Knapweed - Stace, Ragwort Knapweed - NBN, Dusty Miller - RHS, Velvet Centaurea - Wikipedia) 1984 / General - [for some reason it is classed as native by Kew.]
Centaurea montana L. (Perennial Cornflower) / General Scarce An infrequent introduction which sometimes escapes and becomes established on disturbed marginal ground close to habitation such as roadsides, urban lanes, spoil heaps and brownfield sites.
Centaurea graminifolia (Lam.) Muñoz Rodr. & Devesa (Grass-leaved Cornflower?) - Brist. Fl. (as C. seuseana), in Glos. Fl. as C. triumfettii var. seusana (Large flowers of a darker blue and the leaves are more entire) General Extinct "A rare Continental species allied to...[C. cyanus], but the large flowers are of a darker blue and the leaves more entire. Abundant on rubbish in St. Philip's Marsh for several seasons, 1904-7. Now gone. Apparently the sole instance of its occurrence in this country." (White, 1912 [as C. seuseana]).
Centaurea cyanus L. (Cornflower) / General Scarce Extinct as an arable plant but remains as an infrequent casual. It is widely used in ornamental flower mixes, often with additional pink, white and burgundy colour forms and readily escapes from planted sources. A persistent established population was found on cobbles near the Lower Guinea Street Footbridge at Bathurst Basin in 2024 by D. Peters.
Centaurea diffusa Lam. (Small-flowered Star-thistle) - Sandwith (1932) General Extinct [not sure if best placed here] A native of eastern Europe and the Mediterranean; recorded at Baptist Mills in 1922 and Avonmouth Docks in 1929 by C.I. Sandwith.
Centaurea calcitrapa L. (ssp. calcitrapa) (Red Star-thistle) 1926 /- General Extinct Formerly a rare casual of working yards. "Three or four tall, much branched plants at St. Philip's, Bristol, 1904; and several there every year since. In the Station-yard, Portishead, on mill refuse, every year since 1905. On the old quarry ground near Twerton,...1903; Miss Martin and Miss Peck" (White, 1912); Bedminster in 1926 by C.I. Sandwith; and last seen at Avonmouth Docks in 1927 by H.J. Gibbons.
Centaurea iberica Trevir. ex Spreng. (ssp. iberica) (Iberian Star-thistle) 1958 General Extinct A native of eastern Europe and the Middle East; recorded at Baptist Mills in 1927 and 1931 by C.I. Sandwith; St Anne's, Brislington in 1928 by H.J. Gibbons; Ashton Gate in 1939 by ? [BMAG].

[Where's the 1958 record?]

Centaurea pallescens Delile (ssp. pallescens) (Pale Star-thistle?, Pale Centaury, Pale Knapweed - Flora of Israel and adjacent areas) - Sandwith (1932) General Extinct A native of the Middle East; recorded at St Philip's Marsh in 1916 by M. Cobbe and G.C. Druce - thought to be a first and only record for the British Isles.
Centaurea hyalolepis Boiss. (ssp. hyalolepis) (Eastern Star-thistle) - Sandwith (1932) General Extinct recorded at Baptist Mills in 1918 by C.I. Sandwith (as C. pallescens var. hyalolepis); at Ashton Gate in 1937 by ? [BMAG]; and at Avonmouth Docks in 1938 by ? [BMAG].
Centaurea solstitialis L. (ssp. solstitialis) (Yellow Star-thistle) 1925 General Extinct A native of southern Europe; formerly a rare casual of disturbed and cultivated places. "Several plants in St. Philip's Marsh near the Avon in 1898; J. C. Waterfall. Abundant on the Feeder Canal side of the Marsh in 1904. Still there in 1906 and 1908. Casual at Twerton-on-Avon in 1897; S. T. Dunn. In good quantity with sown grasses on Hampton Down, Bath, 1896; D. Fry...Portishead Station-yard, every year since 1905" (White, 1912); Kingswood in 1912? by C.I. Sandwith; railway siding between Shirehampton and Avonmouth in 1917 by C.I. Sandwith; "Near Northwards Asylum [, Frampton Cotterell], J. Bot., 1918, 44" (Riddelsdell, 1948); Avonmouth Docks in 1932? by C.I. Sandwith; Rockhampton, South Gloucestershire in 1956 by ?; and ST47 in 1990s by ? [BSBI record].

[Where's the 1925 record? Need to check Kingswood and Avonmouth Docks records as date not specifically given.]

Centaurea melitensis L. (Maltese Star-thistle) 1932 General Extinct A native of the Mediterranean. "Alien or Casual; on much the same footing as the last species, and perhaps as well worthy of a number, for it seems to be always with us. It is a common weed in South-East Europe, and a frequent occurrence in this country on mill-refuse and tips of city rubbish...On a colliery heap near Kingswood with C. paniculata, but it lasted at the spot a few years longer. On dredgings from the Avon and Floating Harbour deposited in the Black Rock Quarry, 1883-4. A dozen or more plants in St. Philip's Marsh for many years past, and distinctly more plentiful there of late. A patch by the Avon near the Bath Gas Works, Oct. 1895; A. E. Burr. Two plants in an old lias quarry near Twerton, 1904. This quarry is the one described by Mr. S. T. Dunn in Journ. Bot. 1897 as a remarkable site for barley-sifting aliens. It is not so prolific now. Sparingly on a rubbish-tip at St. Anne's, Brislington, 1907. Portishead Station-yard, 1908-9. 'There are specimens of this plant in the Nat. Hist. Mus. Herbarium, South Kensington, gathered on the banks of the Severn, Gloucestershire, in 1869.' - E. G. Baker." (White, 1912). Sandwith (1932) adds no further records, simply stating it as "Common now".
Centaurea diluta Aiton (ssp. diluta) (Lesser Star-thistle) 1982 General Extinct A native of the Iberian Peninsula; recorded at Baptist Mills in 1925-6 by C.I. Sandwith; St Anne's, Brislington in 1928 by H.J. Gibbons; Wapping Wharf in 1928 by I.W. Evans; and at Bath in 1970 by ? [BSBI record].
Centaurea paniculata (ssp. paniculata) (Jersey Knapweed) General Extinct A native of southern Europe; "On a small heap of colliery shale at 'Holly Gess' near Kingswood, from 1881 to 1884. It was not observed afterwards, and the heap has since been carted away." (White, 1912). Also found at Avonmouth Docks in 1934 by ? [BMAG].
Centaurea jacea L. (ssp. jacea) (Brown Knapweed) - Glos. Fl. General Extinct Recorded at "Bristol, towards Horfield" (Riddelsdell, 1948) in 1842 by L.H. Grindon [in The Phytologist I, p. 564] though it seems more likely that this would have been C. nigra.
Centaurea jacea × C. nigra = C. x *gerstlaueri* Erdner (Hybrid Knapweed) - BSBI record [also C. jacea x nigra s.l.] General
Centaurea jacea x C. debeauxii = C. x *moncktonii* C.E. Britton (Brown x Slender Knapweed) - 2 BSBI records + one more on DB General
Centaurea nigra L. (ssp. nigra (non-radiate) and ssp. rivularis (Brot.) Cout. (pseudo-radiate) (both occur) are not worth recognition - Stace) (Common Knapweed) / Grassland Common in a wide range of grassy places including hay meadows, pastures, road verges, railway sidings, field margins, brownfield sites, hedgebanks and sometimes open woodland rides. Very variable in appearance. Plants with pseudo rays were formerly named ssp. rivularis but are no longer recognised as worthy of distinction. It is said to be rare but it is the dominant form in some places such as on the Downs.
Centaurea nigra x *C. debeauxii* (Common x Slender Knapweed) - 1 BSBI record (also on NBN) Grassland Only recorded at in by ? [BSBI record] but intermediates between the two species are frequent and could probably be attributed to this.
Centaurea debeauxii Gren. &. Godr. (ssp. nemoralis (Jord.) Dostál (C. nemoralis Jord. - Kew) (non-radiate) and ssp. thuillieri Dostál (C. thuillieri J. Duvign. & Lambinon - Kew) (pseudo-radiate) not worth recognition - Stace) (Chalk Knapweed - Stace, Slender Knapweed - NBN) Grassland Scarce Appears to be widespread but poorly recorded. Usually found in drier situations on more calcareous soils than C. nigra but not always. Differs from C. nigra in being much more slender in appearance with narrower, more deeply divided stem leaves and diagnostically having narrow cyathia (the black portion), leaving the green portion of the phyllaries clearly exposed (much broader and mostly covering in C. nigra). Clear-cut plants are very distinctive but plants with leaf features closer to C. nigra and slightly less exposed green portions of the phyllaries are common and may be evidence of introgression between the two species. It also generally flowers later than C. nigra, beginning to do so from around mid July.
Centaurea benedicta (L.) L. (var. benedicta) (Cnicus benedictus L.) (Blessed Thistle, Blessed Knapweed Go Botany, Bitter Thistle, St. Benedict's Thistle, Sweet Sultan, Friar's-crown, Lady's Thistle, St. Benedict's Herb - RHS) 1897 General

CARTHAMUS L.

Carthamus tinctorius L. (Safflower) 1978 / General Very Rare recently recorded at ST75H in 2000s by ? (may just be outside region); at ST55P in 2010s by ? [BSBI records]; and two plants were found along with a myriad of other aliens on disturbed ground at Blaise Castle Estate, Bristol in 2023 by D. Peters. Historically recorded at Horfield, Bristol in 1915 by I.W. Evans; St Philip's Marsh and Eastville in 1916 by M. Cobbe and G.C. Druce; Cranbrook Road, Redland in 1917 by Ald. Gardner; Bishops Road in 1929 by H.J. Gibbons; St Anne's, Brislington in 1917 by C.I. Sandwith
Carthamus lanatus L. (ssp. lanatus) (Downy Safflower) 1926 General Extinct A native of southern Europe; recorded at Bedminster and Avonmouth Docks in 1922-6 by C.I. Sandwith; at the latter location again in 1931 by I.W. Evans; and Ashton Gate in 1937 by ? [BMAG].

A form of Carthamus lanatus L., with pure white instead of yellow flowers, was found by C. Sandwith on the N. Somerset side of Bristol in 1937. This matches Sintenis 1957, from the Transcaspian region, in the Kew Herbarium, but appears to have no varietal name [Bristol Botany in 1938, p. 393.].

[Need to check first Avonmouth Docks record as date not specifically stated.]

Carthamus oxyacanthus M. Bieb. (Wild Safflower - Flowers of India, Sharp-spined Safflower? Jeweled Distaff Thistle - GBIF) - 1 record, Glos. Fl. General Extinct A native of the Middle East; recorded at Avonmouth Docks in 1938 by C.I. Sandwith [B.E.C., 1938, p. 46] (Riddelsdell, 1948) [BMAG].

List:

Echinops sphaerocephalus L. (ssp. sphaerocephalus - Kew, GBIF) (Glandular Globe-thistle) / General
Carlina vulgaris L. (ssp. vulgaris - Kew, GBIF) (Carline Thistle) /- Grassland
Arctium lappa L. (ssp. lappa - Kew, GBIF) (Greater Burdock) / General
Arctium lappa x A. minus = A. x nothum (Ruhmer) J. Weiss (Greater x Lesser Burdock) - 1 record General
Arctium tomentosum Mill. (Woolly Burdock) - 1 record General
Arctium minus (Hill) Bernh. (ssp. minus and ssp. pubens (Bab.) P. Fourn. - Stace) (Lesser Burdock) / General
Arctium minus (Hill) Bernh. ssp. pubens (Bab.) P. Fourn. (Lesser Burdock) General
Arctium nemorosum Lej. (Wood Burdock) - all records are probably errors General
Carduus tenuiflorus Curtis (ssp. tenuiflorus - Kew, GBIF) (Slender Thistle) - Coasts
Carduus pycnocephalus L. (ssp. pycnocephalus - Kew, GBIF) (Plymouth Thistle) General
Carduus crispus L. ssp. multiflorus (Gaudin) Gremli (Welted Thistle) / General
Carduus crispus x C. nutans = C. x stangii H. Buek ex Nyman (nothossp. stangii - Kew, GBIF) (Welted x Musk Thistle) Grassland
Carduus nigrescens Vill. ssp. vivariensis (Jord.) Bonnier & Layens (Blackening Thistle - NATURESCENE - Flowers of the Cévennes) - waste ground by Mangotsfield Station in 1896 - tracked down by Mr. S. T. Dunn after detecting it at Bath Flower Show in 1896. - Brist. Fl. General
Carduus acanthoides L. (ssp. acanthoides - Kew, GBIF) (Broad-winged Thistle) - 2 BSBI records (also on NBN) General
Carduus acanthoides x C. nutans = C. x orthocephalus Wallr. (Broad-winged x Musk Thistle) - Sandwith (1932) General
Carduus nutans L. (ssp. nutans - Kew, GBIF) (Musk Thistle) / Grassland
Carduus macrocephalus Desf. (Giant Thistle) - (Sandwith, 1932 [as C. nutans var. macrocephalus]) General
Cirsium eriophorum (L.) Scop. (Woolly Thistle) / Grassland
Cirsium vulgare (Savi) Ten. (ssp. vulgare - Kew, GBIF) (Spear Thistle) / General
Cirsium dissectum (L.) Hill (Meadow Thistle) / Wetland
Cirsium erisithales (Jacq.) Scop. (Yellow Thistle) General
Cirsium acaule Scop. (ssp. acaulon - Kew, GBIF) (Dwarf Thistle) /- Grassland - [bizarrely Kew has it as C. acaulon]
Cirsium acaule x C. palustre = C. x kirschlegeri Sch. Bip. (Stace, NBN) (Dwarf x Marsh Thistle) 1914 Grassland
Cirsium palustre (L.) Scop. (Marsh Thistle) / Wetland
Cirsium arvense (L.) Scop. (var. arvense - Stace, NBN, Kew, GBIF) (Creeping Thistle) / General
Cirsium arvense L. var. incanum (Fisch.) Ledeb. (Creeping Thistle) - Brist. Fl., Glos. Fl. General
Notobasis syriaca (Syrian Thistle) - Glos. Fl. General
Onopordum acanthium L. (ssp. acanthium - Kew, GBIF) (Cotton Thistle) /- General
Onopordum illyricum L. (ssp. illyricum - Kew, GBIF) (Illyrian Thistle) - Sandwith (1932) General
Cynara cardunculus L. (ssp. cardunculus - Kew, GBIF) (var. cardunculus (Cardoon) and var. scolymus (L.) Fiori) (Globe Artichoke) / General
Silybum marianum (L.) Gaertn. (Milk Thistle) General
Serratula tinctoria L. (ssp. tinctoria - Kew, GBIF) (Saw-wort) /- General
Mantisalca salmantica (L.) Briq. & Cavill. (Dagger Flower - GBIF, Flora of North America) 1922 General
Centaurea scabiosa L. (ssp. scabiosa - Kew, GBIF) (var. scabiosa - Stace, NBN) (Greater Knapweed) / Grassland
Centaurea scabiosa L. var. succisifolia E.S. Marshall (Greater Knapweed) - record was sent to BRERC but I can't find it. Grassland
Centaurea stoebe L. ssp. stoebe (Kew, GBIF) (Spotted Knapweed) - [Sandwith, 1932 (as C. maculosa)] - 2 records (on DB as C. maculosa) General - place before C. cineraria?
Centaurea cineraria L. (which sspp.? - ssp. cineraria? - Kew, GBIF) (Silver Knapweed - Stace, Ragwort Knapweed - NBN, Dusty Miller - RHS, Velvet Centaurea - Wikipedia) 1984 / General - [for some reason it is classed as native by Kew.]
Centaurea montana L. (Perennial Cornflower) / General
Centaurea graminifolia (Lam.) Muñoz Rodr. & Devesa (Kew, GBIF) (Grass-leaved Cornflower?) - Brist. Fl. (as C. seuseana), in Glos. Fl. as C. triumfettii var. seusana (Large flowers of a darker blue and the leaves are more entire) General
Centaurea cyanus L. (Cornflower) / General
Centaurea diffusa Lam. (Small-flowered Star-thistle) - Sandwith (1932) General [not sure if best placed here]
Centaurea calcitrapa L. (ssp. calcitrapa - Kew, GBIF) (Red Star-thistle) 1926 /- General
Centaurea iberica Trevir. ex Spreng. (ssp. iberica - Kew, GBIF) (Iberian Star-thistle) 1958 General
Centaurea pallescens Delile (ssp. pallescens - Kew) (Pale Star-thistle?, Pale Centaury, Pale Knapweed - Flora of Israel and adjacent areas) - Sandwith (1932) General
Centaurea hyalolepis Boiss. (ssp. hyalolepis - Kew, GBIF) (Eastern Star-thistle) - Sandwith (1932) General
Centaurea solstitialis L. (ssp. solstitialis - Kew, GBIF) (Yellow Star-thistle) 1925 General
Centaurea melitensis L. (Maltese Star-thistle) 1932 General
Centaurea diluta Aiton (ssp. diluta - Kew, GBIF) (Lesser Star-thistle) 1982 General
Centaurea paniculata (ssp. paniculata - Kew, GBIF) (Jersey Knapweed) - 1 record according to NBN 'small heap of colliery shale at "Holly Gess" near Kingswood, from 1881-1884' - Brist. Fl. General
Centaurea jacea L. (ssp. jacea - Kew, GBIF) (Brown Knapweed) - Glos. Fl. General
Centaurea jacea × C. nigra = C. x gerstlaueri Erdner (Hybrid Knapweed) - BSBI record [also C. jacea x nigra s.l.] General
Centaurea jacea x C. debeauxii = C. x moncktonii C.E. Britton (Brown x Slender Knapweed) - 2 BSBI records + one more on DB General
Centaurea nigra L. (ssp. nigra (non-radiate) and ssp. rivularis (Brot.) Cout. (pseudo-radiate) (both occur) are not worth recognition - Stace) (Common Knapweed) / Grassland
Centaurea nigra x C. debeauxii (Common x Slender Knapweed) - 1 BSBI record (also on NBN) Grassland
Centaurea debeauxii Gren. &. Godr. (ssp. nemoralis (Jord.) Dostál (C. nemoralis Jord. - Kew) (non-radiate) and ssp. thuillieri Dostál (C. thuillieri J. Duvign. & Lambinon - Kew) (pseudo-radiate) not worth recognition - Stace) (Chalk Knapweed - Stace, Slender Knapweed - NBN) Grassland
Centaurea benedicta (L.) L. var. benedicta (Kew, GBIF) Cnicus benedictus L. (NBN) (Blessed Thistle, Blessed Knapweed Go Botany, Bitter Thistle, St. Benedict's Thistle, Sweet Sultan, Friar's-crown, Lady's Thistle, St. Benedict's Herb - RHS) 1897 General
Carthamus tinctorius L. (Safflower) 1978 / General
Carthamus lanatus L. (ssp. lanatus - Kew, GBIF) (Downy Safflower) 1926 General
Carthamus oxyacanthus M. Bieb. (Wild Safflower - Flowers of India, Sharp-spined Safflower? Jeweled Distaff Thistle - GBIF) - 1 record, Glos. Fl. General

Species to add:

Arctium lappa x A. minus = A. x nothum (Ruhmer) J. Weiss (Greater x Lesser Burdock) - 1 record /
Arctium tomentosum Mill. (Woolly Burdock) - 1 record /
Arctium minus L. ssp. pubens (Bab.) P. Fourn. (Lesser Burdock) /
Arctium nemorosum Lej. (Wood Burdock) - all records are probably errors /
Carduus pycnocephalus L. (ssp. pycnocephalus - Kew, GBIF) (Plymouth Thistle) /
Carduus nigrescens Vill. ssp. vivariensis (Jord.) Bonnier & Layens (Blackening Thistle - NATURESCENE - Flowers of the Cévennes) - waste ground by Mangotsfield Station in 1896 - tracked down by Mr. S. T. Dunn after detecting it at Bath Flower Show in 1896. - Brist. Fl. /
Carduus acanthoides L. (ssp. acanthoides - Kew, GBIF) (Broad-winged Thistle) - 2 BSBI records (also on NBN) /
Carduus acanthoides x C. nutans = C. x orthocephalus Wallr. (Broad-winged x Musk Thistle) - Sandwith (1932) General /
Carduus macrocephalus Desf. (Giant Thistle) - (Sandwith, 1932 [as C. nutans var. macrocephalus]) /
Cirsium arvense L. var. incanum (Fisch.) Ledeb. (Creeping Thistle) - Brist. Fl., Glos. Fl. /
Notobasis syriaca (Syrian Thistle) - Glos. Fl. /
Onopordum illyricum L. (ssp. illyricum - Kew, GBIF) (Illyrian Thistle) - Sandwith (1932) /
Centaurea scabiosa L. var. succisifolia E.S. Marshall (Greater Knapweed) - record was sent to BRERC but I can't find it. /
Centaurea stoebe L. ssp. stoebe (Kew, GBIF) (Spotted Knapweed) - [Sandwith, 1932 (as C. maculosa)] - 2 records (on DB as C. maculosa) /
Centaurea graminifolia (Lam.) Muñoz Rodr. & Devesa (Kew, GBIF) (Grass-leaved Cornflower?) - Brist. Fl. (as C. seuseana), in Glos. Fl. as C. triumfettii var. seusana (Large flowers of a darker blue and the leaves are more entire) /
Centaurea diffusa Lam. (Small-flowered Star-thistle) - Sandwith (1932) /
Centaurea pallescens Delile (ssp. pallescens - Kew) (Pale Star-thistle?, Pale Centaury, Pale Knapweed - Flora of Israel and adjacent areas) - Sandwith (1932) /
Centaurea hyalolepis Boiss. (ssp. hyalolepis - Kew, GBIF) (Eastern Star-thistle) - Sandwith (1932) /
Centaurea paniculata (ssp. paniculata - Kew, GBIF) (Jersey Knapweed) - 1 record according to NBN 'small heap of colliery shale at "Holly Gess" near Kingswood, from 1881-1884' - Brist. Fl. /
Centaurea jacea L. (ssp. jacea - Kew, GBIF) (Brown Knapweed) - Glos. Fl. /
Centaurea jacea × C. nigra = C. x gerstlaueri Erdner (Hybrid Knapweed) - BSBI record /
Centaurea jacea x C. debeauxii = C. x moncktonii C.E. Britton (Brown x Slender Knapweed) - 2 BSBI records + one more on DB /
Centaurea nigra x C. debeauxii (Common x Slender Knapweed) - 1 BSBI record (also on NBN) /
Centaurea debeauxii Gren. &. Godr. (ssp. nemoralis (Jord.) Dostál (C. nemoralis Jord. - Kew) (non-radiate) and ssp. thuillieri Dostál (C. thuillieri J. Duvign. & Lambinon - Kew) (pseudo-radiate) not worth recognition - Stace) (Chalk Knapweed - Stace, Slender Knapweed - NBN) /
Carthamus oxyacanthus M. Bieb. (Wild Safflower - Flowers of India, Sharp-spined Safflower? Jeweled Distaff Thistle - GBIF) - 1 record, Glos. Fl. /

Serratula tinctoria L. var. integrifolia Wallr. (Saw-wort) - Brist. Fl. and Glos. Fl. (as var. lanceifolia) needs investigating - no longer recognised