Symphyotrichum ×amethystinum

(Nuttall) G. L. Nesom
Phytologia 77: 294. 1995.
Common names: Amethyst aster
Basionym: Aster amethystinus Nuttall Trans. Amer. Philos. Soc., n. s. 7: 294. 1840
Synonyms: Virgulus ×amethystinus (Nuttall) Reveal & Keener
Treatment appears in FNA Volume 20. Treatment on page 497. Mentioned on page 471, 472, 483, 487, 488, 498.

Perennials, cespitose, 30–120 cm; with thick, woody, short-branched caudices at ends of fleshy rhizomes. Stems 1–5+, erect (light brown to grayish brown), densely hispidulo-hirsute. Leaves light green, thin to firm; basal withering by flowering, sessile, blades oblanceolate, 10–40 × 3–10 mm, attenuate, margins usually entire, rarely remotely serrate, piloso-ciliate, apices obtuse, rounded to mucronulate, faces sparsely to moderately strigose; proximal cauline sometimes persistent by flowering, sessile, blades linear or oblong to elliptic-oblanceolate, 40–60 × 3–10 mm, bases rounded or slightly clasping, margins entire, scabrous, apices acute to obtuse, faces ± copiously hirsute; distal sessile, blades oblanceolate, 15–45 × 2–3(–4.5) mm, progressively reduced distally, bases cuneate, margins entire, apices acute, white-spine-tipped, faces sparsely strigose. Heads in ample, leafy, paniculiform arrays, branches ascending, sometimes secund (heads often crowded). Peduncles hispid, bracts 1–3+, oblong-lanceolate, 3–5 mm, not grading into phyllaries. Involucres campanulate to hemispheric, 4–6 mm. Phyllaries in 3–5 series, linear-lanceolate, ± unequal to subequal, bases ± indurate, margins hyaline proximally, outer distally hispido-scabrous, green zones diamond-shaped, restricted to distal 1/2–1/4, apices (outer) spreading to reflexed, acute, subspinulose, (inner) acuminate, purplish, faces (outer) scabroso-puberulent or strigose, eglandular, inner distally stipitate-glandular. Ray florets 20–35; corollas azure blue to violet or lavender, laminae 5–10 × 0.6–1.2 mm. Disc florets 20–30+; corollas light yellow turning pinkish to purple, 3–4 mm, tubes ca. 1/2 narrowly funnelform throats, lobes triangular, 0.5–0.7 mm, glabrous. Cypselae dull purple or brown, obovoid, not compressed, 1.5–2 mm, 7–9-nerved, faces densely sericeous; pappi tan to tawny, sometimes rose to violet-tinged, 3.5–5.5 mm. 2n = 10.


Phenology: Flowering Aug–Oct.
Habitat: Fields, prairies, disturbed grounds
Elevation: 200–400 m

Distribution

V20-1116-distribution-map.gif

Ont., Colo., Conn., Ill., Ind., Iowa, Ky., Md., Mass., Minn., Mo., Nebr., N.J., N.Y., N.Dak., Pa., R.I., Vt., Wash., Wis.

Discussion

Symphyotrichum ×amethystinum is the F1 hybrid between S. ericoides and S. novae-angliae, encountered sometimes throughout the area where the two parental species co-occur. It is morphologically intermediate; it has non-spiny, sparsely stipitate-glandular phyllaries and rose-violet rays in mid-sized heads. Forma leucerythros Bemis and forma leucos Bemis have been described within this hybrid and may represent recombinants or normal population color variants.

Selected References

None.

Lower Taxa

None.

Luc Brouillet +, John C. Semple +, Geraldine A. Allen +, Kenton L. Chambers +  and Scott D. Sundberg† +
(Nuttall) G. L. Nesom +
Aster amethystinus +
Amethyst aster +
Ont. +, Colo. +, Conn. +, Ill. +, Ind. +, Iowa +, Ky. +, Md. +, Mass. +, Minn. +, Mo. +, Nebr. +, N.J. +, N.Y. +, N.Dak. +, Pa. +, R.I. +, Vt. +, Wash. +  and Wis. +
200–400 m +
Fields, prairies, disturbed grounds +
Flowering Aug–Oct. +
Virgulus ×amethystinus +
Symphyotrichum ×amethystinum +
Symphyotrichum subg. Virgulus +
species +