Aster 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 : 112-113

7. Aster L. 2

Herbs, usually perennial. Leaves alternate or basal, simple. Capitula small to medium, solitary or in corymbs or panicles. Involucral bracts in 2 nearly equal rows, or imbricate in 3-several rows with the outer much shorter than the inner. Receptacle flat or convex. Outer florets ligulate, female or sterile, in 1 row; ligules blue, violet, purple, pink or white, sometimes absent. Inner florets tubular, hermaphrodite, yellow, often becoming purple. Achenes oblong, usually compressed, more or less hairy and often glandular. Pappus-hairs scabrid, whitish to yellowish or reddish, often unequal, in 1-2 indistinct rows.

The recognition as a separate genus of Sect. Galatella (20-23), possibly also including Sect. Aegaeaster (24) and Linosyris (25-27), though probably desirable, requires thorough investigation of the whole genus.

Many species have been introduced into cultivation in Europe from North America. From European gardens some of the original introductions and their accidental or deliberately raised hybrids have escaped, and continue to do so. Such escapes have long been established on river-banks or in fens, where they are fully naturalized and may form quite uniform populations, though not necessarily easily matched with North American species. Populations on waste ground, railway-banks etc. are often much more variable and here the delimitation of taxa is necessarily arbitrary and the identification of specimens sometimes impossible.

Literature: I. Novopokrovsky, Not. Syst. (Leningrad) 11: 211-233 (1949). M. Onno, Biblioth. Bot. (Stuttgart) 106: 1-83

(1932). R. von Soó, Bot. Közl. 22: 56-64 (1925). A. Thellung, Allgem. Bot. Zeitschr. 19: 87-89, 101-112, 132-140 (1913). F. N. Williams, Jour. Bot. (London) 43: 78 -89 (1905). 1 Ligules absent

2 Leaves and outer involucral bracts densely grey-tomentose

26. oleifolius 2 Leaves not densely grey-tomentose

3 Leaves glandular-punctate

4 Lower leaves petiolate; plant densely greyish-setulose

16. willkommii 4 All leaves sessile; plant glabrous, scabrid or arachnoid-hairy

5 Inner involucral bracts acuminate 25. linosyris 5 Inner involucral bracts subacute to rounded

6 Involucral bracts glabrous, viscid-shining; leaves distinctly 3-veined at least near the base 20. sedifolius 6 Outer involucral bracts lanate; leaves 1-veined

27. tarbagatensis 3 Leaves eglandular

7 Inner involucral bracts subobtuse to rounded; stem glabrous; leaves ± succulent, the lower long-petiolate

19. tripolium 7 Inner involucral bracts subacute to acuminate; leaves not succulent, all sessile

8 Leaves 1-veined, acicular or linear to linear-lanceolate

9 Capitula solitary or few; stem fioccose 24. creticus 9 Capitula numerous, in dense corymbs; stem weakly scabrid 25. linosyris 8 Leaves conspicuously 3-veined at least near the base, linear-lanceolate to lanceolate

10 Outer and middle involucral bracts abruptly contracted into a long subulate apex, somewhat lanate; leaves arachnoid-hairy 22. kirghisorum 10 Outer and middle involucral bracts subacute; leaves scabrid 20. sedifolius 1 Ligules present

11 Stems leafless 18. bellidiastrum 11 Stems leafy, at least in the lower half

12 Ligules sterile, with undivided styles usually shorter than the corolla-tube

13 Involucral bracts in up to 8 rows; leaves strongly dimorphic, the basal oblanceolate to spathulate, the cauline acicular 23. aragonensis 13 Involucral bracts in 3-5 rows; leaves not strongly dimorphic

14 Leaves glandular-punctate at least above

15 Lower leaves petiolate; outer and middle involucral bracts with a subulate apex 21. albanicus 15 All leaves sessile; involucral bracts all subacute or the inner obtuse 20. sedifolius 14 Leaves eglandular

16 Outer and middle involucral bracts abruptly contracted into a long, subulate apex; leaves arachnoid-hairy

22. kirghisorum 16 Involucral bracts all subacute or the inner obtuse; leaves scabrid to subglabrous 20. sedifolius 12 Ligules female, fertile, with 2 style-branches; styles always exceeding the corolla-tube

17 Involucral bracts in 2(—3) indistinct rows, all nearly equal

18 Basal and lower cauline leaves petiolate, the upper sessile,

entire 17. alpinus 18 All leaves sessile, auriculate at base, remotely and coarsely toothed 14. pyrenaeus 17 Involucral bracts in (2—)3—5 rows, often very unequal

19 Basal and usually some of the cauline leaves petiolate and with the base of the lamina cordate to subcordate

20 Inflorescence glandular-puberulent 1. macrophyllus 20 Inflorescence eglandular

21 Lower leaves 6-14 cm wide; outer involucral bracts more than 1 mm wide 2. schreberi 21 Lower leaves 3—6(—7) cm wide; outer involucral bracts not more than 1 mm wide 3. divaricatus 19 Basal and lower cauline leaves petiolate and with the base of the lamina not cordate, or sometimes sessile 22 Capitula usually 10 or fewer 23 Plant with numerous sessile glands; leaves entire

16. willkommii 23 Plant eglandular, or with a few scattered glands; leaves toothed or entire

24 Outer involucral bracts subobtuse to rounded, subspathulate; middle and upper cauline leaves narrowed at base 15. amellus

24 All involucral bracts acute; cauline leaves somewhat auriculate, semiamplexicaul 13. sibiricus 22 Capitula more than 10 25 Ligules about as long as pappus; annual or biennial

12. squamatus 25 Ligules much longer than pappus; usually perennial

26 Involucral bracts subobtuse to rounded

27 Leaves glabrous and ± succulent 19. tripolium

27 Leaves hairy, not succulent 15. amellus

26 Involucral bracts acute or rarely mucronate

28 Inflorescence glandular

29 Leaves auriculate 4. novae-angliae

29 Leaves not auriculate 16. willkommii

28 Inflorescence eglandular

30 Most cauline leaves not more than 1 cm wide

31 Outer involucral bracts with subulate, green apex

11. pilosus

31 Outer involucral bracts without subulate, green apex 10. lanceolatus

30 Most cauline leaves more than 1 cm wide

32 Leaf-bases not auriculate or semiamplexicaul;

longest involucral bracts 4-5-5 mm; ligules usually white 10. lanceolatus

32 Leaf-bases auriculate or semiamplexicaul; longest involucral bracts 5-12 mm; ligules violet-blue

33 Leaves glaucous above; involucral bracts very unequal, appressed, green only in the middle

6. laevis

33 Leaves not glaucous above; outer involucral bracts about as long as inner, with lax or recurved apex, green throughout

34 Stem uniformly hispid, except sometimes at base

5. puniceus

34 Stem glabrous or with hairs in longitudinal bands (7-9). novi-belgii group