Centaurea alba, L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1976, Flora Europaea. Volume 4. Plantaginaceae to Compositae (and Rubiaceae), Cambridge University Press : 287-288

167. C. alba L. , Sp. Pl. 914 (1753).

Biennial or perennial. Stems 10-80 cm, erect, rarely ascending from the base, branched from the lower half, rarely simple. Leaves arachnoid-lanate to subglabrous, rarely viscid; lower 1- to 2(-3)-pinnatisect to lyrately lobed, rarely undivided, the segments linear to ovate, entire to dentate; middle pinnately divided, rarely undivided, the segments linear, lanceolate to oblong; upper pinnately divided or lobed, the segments linear-filiform to -lanceolate; uppermost linear to lanceolate, undivided to 2- to 3-fid. Capitula usually more than 10, not in clusters. Involucre 8-22 x 6-25 mm, ovoid to globose or ovoid-cylindrical; appendages mostly covering the bracts, orbicular or broadly ovate, concolorous or with a dark or paler centre, the margin entire or denticulate- or lacerate-fimbriate, the apex emarginate, with a soft mucro or arista, or muticous. Florets pink or purple, rarely white. Achenes 2-5^4 mm; pappus absent, or | as long to somewhat longer than the achene. 2л = 18. Dry places. S. Europe. Al Bu Gr He Hs It Ju Lu Rm Si.

This species contains many variants separable only on minute but distinctive characters; whilst these variants have usually been given specific status, they are here regarded as subspecies.

1 Lower leaves undivided or lyrately lobed

2 Involucre 20-25 mm in diameter, ovoid-globose

(e) subsp. tenoreana 2 Involucre 6-10 mm in diameter, ovoid (t) subsp. subciliaris 1 Lower leaves 1- to 3-pinnatisect or -partite

3 Leaves viscid, glandular-punctate; involucre 20-25 mm in diameter (s) subsp. princeps 3 Leaves not viscid; involucre not more than 20 mm in diameter

4 Involucre 7-12 mm in diameter

5 Appendages white, often with green centre

6 Perennial; stem divaricately branched; leaves arachnoidlanate; pappus I as long as achene (o) subsp. formanekii 6 Biennial; stem sparingly branched, the branches erect; leaves subglabrous or greyish-green; pappus as long as achene (q) subsp. euxina 5 Appendages with brown to black centre

7 Involucre 10-12 mm in diameter (p) subsp. vandasii 7 Involucre 6-10 mm in diameter

8 Leaves arachnoid or white-tomentose; involucre ovoid; appendages entire or sometimes somewhat lacerate, with a brown centre

9 Leaves white-tomentose; involucre 10 mm in diameter; appendages entire or sometimes somewhat lacerate,

the apex muticous (g) subsp. diomedea 9 Leaves arachnoid; involucre 7-8 mm in diameter; appendages entire, the apex mucronate

10 Pappus absent (1) subsp. epapposa 10 Pappus present (m) subsp. caliacrae 8 Leaves green or greyish-green; involucre ovoid-globose or ovoid-cylindrical; appendages lacerate- or fimbriatedenticulate, with a blackish- or reddish-brown centre

11 Stem with simple branches; pappus | as long as achene

(a) subsp. costae 11 Stem paniculately or corymbosely branched; pappus absent or | as long as achene

12 Stem paniculately branched with virgate branches; leaves green; involucre ovoid-cylindrical; appendages with reddish-brown centre; pappus j as long as achene (b) subsp. latronum 12 Stem corymbosely branched with erect branches; leaves greyish-green; involucre ovoid-globose; appendages with blackish-brown centre; pappus absent (f) subsp. pestalottii 4 Involucre 10-16 mm in diameter

13 Appendages white, sometimes with yellow or greyishbrown centre

14 Leaves densely lanate or whitish-tomentose

15 Stem corymbosely branched; leaves lanate, the lower with linear-lanceolate segments; involucre 12-15 mm

in diameter, ovoid-globose; appendages entire, covering bracts (c) subsp. alba 15 Stem paniculately branched; leaves white-tomentose,

the lower with few, oblong to lanceolate segments; involucre 10-12 mm in diameter, globose; appendages undulately erose, not covering bracts

(n) subsp. leucomalla 14 Leaves puberulent, or setulose-puberulent and sparsely lanate

16 Leaves puberulent, the lower with lanceolate segments; involucre 11-12 mm in diameter, ovoid; appendages with yellow centre, the apex muticous; pappus ł as long as achene; stem up to 60 cm (d) subsp. splendens

16 Leaves setulose-puberulent and sparsely lanate, the lower with linear-filiform segments; involucre 12-16

mm in diameter, subglobose; appendages with greyish-brown centre, the apex aristate; pappus somewhat longer than achene; stem up to 20 cm

(h) subsp. albanica 13 Appendages with brown or black centre 17 Mature leaves white-tomentose, the lower with linearoblong segments (r) subsp. heldreichii 17 Mature leaves green, glabrescent, the lower with linear or linear-lanceolate segments 18 Leaves puberulent, the lower pinnatisect with linear segments; involucre 17-20 mm in diameter; appendages with a triangular-lanceolate central spot

(i) subsp. ipecensis 18 Leaves tomentose, the lower 2-pinnatifid with lanceolate segments; involucre 12-14 mm in diameter; appen­

dages with a broadly ovate or orbicular central spot

19 Leaves soft, the segments oblong-lanceolate; appendages with black central spot (j) subsp. deusta

19 Leaves coriaceous, the segments linear to lanceolate;

appendages with brown or pale brown central spot

20 Segments of leaves linear-filiform; appendages with pale brown centre, aristate (h) subsp. albanica

20 Segments ofleaves linear-lanceolate; appendages with brown centre (k) subsp. brunnea