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Plant Family: Asteraceae | Genus: Aster Family index | Genus index | Search Page
rayless alkali aster, rayless aster

Synonyms: Brachyactis angusta (Lindl.) Britt. ; Brachyactis ciliata (Ledeb.) Ledeb. ssp. angusta (Lindl.) A.G. Jones ; Brachyactis ciliata (Ledeb.) Ledeb. ; Symphyotrichum ciliatum (Ledeb.) Nesom ; Tripolium angustum Lindl.

Description: Annual herb with a short taproot, 10 - 70 cm tall. Stems erect, branching near the base, yellowish green often red-tinged, and smooth or sparsely hairy near leaf axils. Lower stem leaves unstalked, bluish green, widest past the middle, base tapered, margins entire, surface hairy, usually dying back before flowering. Upper stem leaves unstalked, 3 - 10 cm long, 1 - 9 mm wide (branch leaves smaller), bluish green, linear to lance-shaped, margins entire with short hairs, surface smooth. Inflorescence wide-spreading with few to many heads. Peduncles smooth and short. Involucres 6 - 10 mm long, cup-shaped. Phyllaries in 3 - 4 nearly equal rows, 4 - 8 mm long, linear to narrow elliptic, with rough margins. Heads consist of 40 - 80 ray and disc florets, though appearing rayless. Ray florets 2 mm long, slender, tube-shaped, lacking a showy petal (strap). The ray florets only contain female parts, and the style is long and pink. Disc florets yellow, 3.5 - 5 mm long, tubular to funnel-shaped, with both male and female reproductive parts present. Pappus of hairs in two or three whorls, white or faintly pink, considerably longer than disc corolla tube. Achenes 1.5 - 2.5 mm long, gray to whitish, often purple-streaked, oblong, slightly compressed.

Similar Species: Aster brachyactis, which appears to have no rays in the flower heads, can be confused with A. subulatus, but that species has very short, white to purple rays, a succulent stem, and is completely hairless.
Aster subulatus

Flowering: Late August to October.

Habitat and Ecology: Common in disturbed ground, especially along highways where road salt accumulates. The species occasionally grows in industrial and waste areas and along railroad tracks.

Notes: Unlike most asters, this species appears to be lacking ray florets. This trait gives it the common name, rayless aster. However, ray florets are present, but the petals are absent or greatly reduced.

Etymology: Aster comes from the Greek word for star, referring to the flower head. Brachyactis comes from the Greek word for short rays.

Regional Status: Non-native.

References:
- Jones, A. G. 1989. Aster and Brachyactis in Illinois. Illinois Natural History Survey Bulletin. 34(2): 139-194.
- Semple, J.C., S.B. Heard and L. Brouillet. 2002. Cultivated and native asters of Ontario (Compositae: Astereae): Aster L. (including Asteromoea Blume, Diplactis Raf. and Kalimeris (Cass.) Cass.), Callistephus Cass., Galatella Cass., Doellingeria Nees, Oclemena E.L. Greene, Eurybia (Cass.) S.F. Gray, Canadanthus Nesom, and Symphyotrichum Nees (including Virgulus Raf.). U. Waterloo. Biol. Series No. 41: 1-134.

Aster brachyactis
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Aster brachyactis
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