Sonchus oleraceus

      
Annual Sow-Thistle

G. F. Ledingham Herbarium
University of Regina

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Oleraceus:  Answers to key questions in Budd's Flora and Flora of Alberta leading to this species.  
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annuals growing from deep taproots; NOT perennials from creeping rootstocks

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basal auricles of clasping leaves acutely pointed; NOT rounded

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flowering heads 1.5-2.5 cm across; NOT 3-5 cm across

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fruiting involucre 9-13 mm high; NOT 14-24 mm high

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fruiting involucre glabrous

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achenes striate and transversely wrinkled; NOT [3-ribbed on each side, smooth]

 
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Sonchus: Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus. 
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juice milky; NOT watery

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stem NOT diffusely branched

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plants with at least some cauline leaves; NOT scapose

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plants with normal stem leaves; leaves NOT [all basal or with a few reduced leaves on the stem]

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leaves broader and leaf-like; leaves NOT [few, cauline, mostly linear or reduced to scales]

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heads few to many, rarely solitary

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involucre of 2 or more series; NOT uniseriate

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none of the florets tubular, heads all ligulate

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flowers all perfect

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flowers yellow

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stamens united to form a tube around the pistil

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achenes flattened, at least twice as wide as thick

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achenes beakless

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pappus well developed, at least in part of capillary bristles; pappus NOT of minute scales, NOT absent

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pappus simple, consisting of bristles only; NOT [pappus double, the outer ring consisting of 5 small scale-like appendages, the inner ring bristles]

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pappus bristles simple; NOT plumose

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pappus white; NOT brownish