Family: Asteraceae
Onopordum acaulon
Citation:
L., Sp. Pl. edn 2:1159 (1763).
Synonymy: Not Applicable Common name: Stemless thistle, stemless onopordum, horse thistle.
Description:
Biennial herb, rosette-forming, with a large tap root; stem absent; leaves oblanceolate to elliptic, to 50 cm long, to 12 cm wide, pinnatifid to pinnatipartite with triangular lobes, with numerous yellowish spines to 1 cm long, densely grey-white-woolly on both surfaces.
Capitula solitary or clustered, sessile or on peduncles to 3 cm long in the centre of the rosette, 4-6 cm diam.; involucral bracts lanceolate, 2-3 cm long, acuminately tapered into a straight spine, glabrous, green, all erect or the outer series recurved; corolla 22-25 mm long, white.
Achenes compressed-obovoid, 4-ribbed, faintly wrinkled, 4-5 mm long; pappus bristles 2-3 cm long, buff, barbellate.
Published illustration:
Cunningham et al. (1982) Plants of western New South Wales, p. 726.
Distribution:
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Locally abundant weed of pastures, arable land and roadsides, chiefly on heavy soils.
S.Aust.: FR, EA, EP, NL, MU, YP, SL, KI, SE. W.Aust.; N.S.W.; Vic. Native to Spain and southern France.
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Conservation status:
naturalised
Flowering time: Oct. — Dec.
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SA Distribution Map based
on current data relating to
specimens held in the
State Herbarium of South Australia
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Biology:
Two subspecies of O. acaulon are recognised in Europe; however, S.Aust. populations are not clearly refertable to either subspecies and may have been derived from both.
Author:
Not yet available
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