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Electronic Flora of South Australia genus Fact Sheet

Family: Compositae
Sonchus

Citation: L., L., Sp. Pl. 793 (1753).

Derivation: Greek sonchos, Latin sonchus; applied in classical times to S. asper and S. oleraceus.

Synonymy: Actites Lander, Telopea 1:130 (1976).

Common name: Perennial sow-thistle, corn sow-thistle.

Description:
Perennial 30-150 cm high, with creeping rhizomes; stems erect, unbranched, glabrous; basal leaves narrowly oblanceolate, pinnatifid, denticulate, 4-15 cm long, glabrous; cauline leaves oblanceolate to lanceolate, acute, with rounded basal auricles, runcinately or sinuately pinnatifid to pinnatipartite with triangular lobes, minutely spiny on the margins, 5-25 cm long, 2-8 cm wide, stiffly herbaceous, glabrous.

Peduncles 1-5 cm long with glandular hairs; capitula in a corymbose panicle; involucres 10-15 mm long; bracts glandular-pubescent, ciliate at the apex; florets 15-230; ligules c. 10 mm long.

Achenes moderately compressed, ellipsoid, 2.5-3.5 mm long, rugulose all over, with very narrow margins, dark-brown; pappus c. l cm long, persistent.

Published illustration: Ross-Craig (1963) Drawings Brit. Pl. 18:t. 37.

Distribution:  A weed of cultivated land.

  Native to Europe.

Biology: Recorded from Clare in 1960, and possibly no longer present in this State.

Key to Species:
1. Achenes rugose between the fibs, with narrow marginal ridges; leaves softly herbaceous
 
2. Rhizome present; achenes elliptic
S. arvensis 1.
2. Rhizome absent; schenes oblanceolate
 
3. Involucres lacking tomentum; ligules 5-6 mm long, subequal to the corolla tube
S. oleraceus 5.
3. Involucres tomentose at the base when young; ligules 8-9 mm long, longer than the corolla tube
S. tenerrimus 6.
1. Achenes not rugose, with broad wing-like marginal ridges; leaves stiffly herbaceous to coriaceous
 
4. Rhizome present; achenes narrowed distally, 5-7 mm long
S. megalocarpus 4.
4. Rhizome absent; achenes elliptic, 2-4 mm long
 
5. Leaves mostly pinnatipartite to deeply pinnatifld; achene margins wholly scabrous
S. asper subsp. glaucescens 2b.
5. Leaves denticulate to shallowly pinnatifid; achene margins smooth or scabrous near the ends only
 
6. Stem base less than 1 cm diam., herbaceous; pollen grains 32-42 (m diam
S. asper subsp. asper 2a.
6. Stem base 1-2 cm diam., more or less woody; pollen grains 45-46 (m diam
S. hydrophilus 3.

Author: Not yet available


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