Erigeron 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 : 116-117

8. Erigeron L. 1

(incl.

Stenactis Cass. )

Annual, biennial or perennial herbs. Flowering stems usually with long eglandular hairs, the pubescence increasing progressively from below upwards. Leaves usually entire, the basal obovate-spathulate, somewhat petiolate, the cauline lanceolate to linear-lanceolate. Flowering stems with 1 to several capitula in a lax, corymbiform or elongate panicle. Ligulate florets female, usually exceeding the involucre; tubular florets yellow, either all similar, hermaphrodite or the outer florets female, filiform, the inner hermaphrodite. Achenes pubescent, sometimes dimorphic; pappus of hairs, or of short scales in ligulate florets and an outer row of scales and an inner row of long hairs in tubular florets.

Most of the montane species (5-17) have isolated local variants which do not appear to merit the specific or subspecific status accorded them in the past. Intermediates exist between many of the species recognized here; to what extent this is caused by hybridization is unknown. Much confusion has resulted from lack of attention to the pubescence and shape of the oldest basal leaves, and from a reluctance to search for the filiform female florets in trimorphic species. Considerable importance has been attached to this character, but it is not known whether plants of trimorphic species can occasionally produce dimorphic progeny, or vice versa, nor how the character is inherited. Ligulate florets with the ligules broken off can be mistaken for filiform florets.

Literature: F. Vierhapper, Beih. Bot. Centr. 19 (2): 385-560 (1906). The following three perennial species from North America occasionally escape from cultivation:

E. glaucus Ker-Gawler , Bot. Reg. 1: t. 10 (1815), has basal rosettes of somewhat fleshy, glabrescent leaves and ascending to erect flowering stems with 1-4 large capitula with lilac or white ligules. The flowering stems, cauline leaves and involucre have dense, long eglandular and short glandular hairs.

E. speciosus (Lindley) DC. , Prodr. 5: 284 (1836) ( Stenactis speciosa Lindley ), lacks basal rosettes at anthesis and has tall, slender, glabrous, ridged stems with 1-4 large capitula with violet or blue ligules. The cauline leaves are ciliate, the lower oblanceolate, the upper lanceolate.

E. philadelphicus L. , Sp. Pl. 863 (1753) ( Stenactis philadelphica (L.) Hayek), is similar to E. speciosus but often biennial; the stems and cauline leaves are pubescent, the upper cauline leaves are semi-amplexicaul and there are 4-15 capitula. The ligules are deep purplish, rarely white. 1 Stems procumbent to ascending; lower cauline leaves usually 3-lobed 2. karvinskianus 1 Stems erect; lower cauline leaves entire or serrate, not 3-lobed

2 Lower cauline leaves ovate-lanceolate, often serrate; ligules white or pale blue 1. annuus 2 Lower cauline leaves narrowly spathulate or almost linear, entire; ligules lilac, less commonly white

3 Capitula without filiform female florets between the tubular and ligulate florets (florets dimorphic)

4 Capitulum more than 2 cm wide; ligules 7-13 mm, remaining flat on drying (N. Ural) 17. silenifolius 4 Capitulum less than 2 cm wide; ligules less than 8 mm, becoming involute on drying

5 Flowering stems and involucral bracts with dense, short glandular and longer eglandular hairs (Sierra Nevada)

13. major 5 Indumentum variable but short glandular hairs absent

6 Involucral bracts sparsely pubescent to almost glabrous,

usually green to the apex 12. glabratus 6 Involucral bracts usually densely pubescent; apex lilac

7 Basal rosettes densely caespitose; whole plant densely pubescent; ligules deep lilac 16. frigidus 7 Basal rosettes laxly caespitose; basal leaves glabrous to sparsely pubescent; ligules white or pale lilac

8 Involucral bracts with long white hairs; flowering stems usually well exserted from basal rosettes 14. uniflorus 8 Involucral bracts with purple hairs; flowering stems often scarcely exserted from the basal rosettes

15. humilis 3 Capitula with filiform female florets between the tubular and ligulate florets (florets trimorphic)

9 Flowering stems with conspicuous glandular hairs at least above

10 Flowering stems erect, branched in the upper f; capitula

3-10 5. atticus 10 Flowering stems ascending, branched at or below the middle; capitula 1-5 6. gaudinii

9 Flowering stems without conspicuous glandular hairs

11 Annual or short-lived perennial; basal rosette usually absent at anthesis; cauline leaves usually more than 10;

capitula usually more than 8

12 Ligules 1-11 times as long as the involucral bracts 3. acer 12 Ligules l|-2 times as long as involucral bracts

4. orientalis

11 Perennial; basal rosette present at anthesis; cauline leaves usually fewer than 10; capitula rarely more than 8

13 Basal leaves with usually short, dense, crispate hairs

14 Flowering stems usually more than 10 cm; capitula 1 to several 7. alpinus

14 Flowering stems usually less than 10cm; capitula solitary 8. epiroticus

13 Basal leaves ciliate, otherwise glabrous or very sparsely pubescent

15 Flowering stems not stiffly erect; youngest basal leaves sparsely pubescent 11. borealis

15 Flowering stems stiffly erect; basal leaves ciliate, otherwise glabrous or almost so

16 Basal leaves usually less than 6 mm wide; involucral bracts up to 1 mm wide, moderately pubescent

9. neglectus

16 Basal leaves up to 14 mm wide; involucral bracts usually more than 1 mm wide, densely pubescent

10. nanus