Sonchus arvensis
 
Perennial Sow-Thistle

Upper Leaf Top

Moose Mountain Provincial Park
20-Aug-2005

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

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flowering heads 3-5 cm across; NOT [flowering heads not over 2.5 cm across]

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

 

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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 [juice watery]

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stem not diffusely branched

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plants with at least some cauline leaves; NOT [plants scapose, leaves all basal]

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leaves broader and leaf-like; NOT [leaves narrowly linear or scale-like]

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heads few to many; NOT [heads solitary]

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involucre of 2 or more series; NOT [involucre uniseriate or biseriate] (FOA)

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flowers all ligulate

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flowers all perfect; NOT [flowers pistillate or neuter]

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flowers yellow

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stamens united to form a tube around the pistil (Checked Above)

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achenes flattened, at least twice as wide as thick

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achenes beakless; NOT [achenes beaked, the pappus borne on a disc at the tip]

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pappus well developed, at least in part of capillary bristles; NOT [pappus of minute scales or none]

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pappus not scale-like at the base, entirely of capillary bristles; NOT [pappus scale-like at the base, with plumose terminal bristles]

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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 [pappus bristles plumose]

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pappus white; NOT [pappus brownish]