Family: Asteraceae
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:
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A weed of cultivated land.
Native to Europe.
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Biology:
Recorded from Clare in 1960, and possibly no longer present in this State.
Key to Species:
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1. Achenes rugose between the fibs, with narrow marginal ridges; leaves softly herbaceous |
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2. Rhizome present; achenes elliptic |
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S. arvensis 1. |
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2. Rhizome absent; schenes oblanceolate |
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3. Involucres lacking tomentum; ligules 5-6 mm long, subequal to the corolla tube |
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S. oleraceus 5. |
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3. Involucres tomentose at the base when young; ligules 8-9 mm long, longer than the corolla tube |
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S. tenerrimus 6. |
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1. Achenes not rugose, with broad wing-like marginal ridges; leaves stiffly herbaceous to coriaceous |
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4. Rhizome present; achenes narrowed distally, 5-7 mm long |
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S. megalocarpus 4. |
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4. Rhizome absent; achenes elliptic, 2-4 mm long |
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5. Leaves mostly pinnatipartite to deeply pinnatifld; achene margins wholly scabrous |
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S. asper subsp. glaucescens 2b. |
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5. Leaves denticulate to shallowly pinnatifid; achene margins smooth or scabrous near the ends only |
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6. Stem base less than 1 cm diam., herbaceous; pollen grains 32-42 (m diam |
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S. asper subsp. asper 2a. |
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6. Stem base 1-2 cm diam., more or less woody; pollen grains 45-46 (m diam |
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S. hydrophilus 3. |
Author:
Not yet available
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