Aquatic and Wetland Vascular Plants of the Northern Great Plains
49. Asteraceae, the Aster Family
14. Senecio L. -- Ragwort1. Senecio congestus (R.Br.) DC. -- Swamp ragwort
Fibrous-rooted annual or biennial 1.5-10 dm tall; stems hollow, especially toward the base, sparsely to densely villous. Leaves basically all similar in shape, oblong-linear to oblong-lanceolate or the lower ones often spatulate, 4-20 cm long, 0.5-6 cm wide, or the basal leaves occasionally larger, glabrous or villous in patches, blunt to rounded at the apex, entire to coarsely toothed or sinuate-toothed, sometimes crisped, the basal and lower leaves usually petiolate, often deciduous, the middle and upper cauline leaves sessile, with winged to auriculate-clasping bases. Heads several to many, in one or more congested clusters, 1-1.5 cm across; involucre 4-8 mm high, the bracts pale and scarious toward the tip, darker at the base; rays pale yellow, 4-9 mm long. Achenes 1.5-2.5 mm long, glabrous; pappus bristles very fine and numerous, strongly accrescent. Late May--early Aug. Shores and mud flats; frequent across n ND and w MN, less common s to se SD; (Circumpolar, s in Am. to Que., n IA, e SD and Alta.).
Senecio hydrophilus Nutt. rarely occurs in the w part of our region, with records from Pennington Co., SD and Albany Co., WY. The plant is hollow-stemmed like S. congestus, but is a glaucous perennial with glabrous stems and leaves and with the cauline leaves greatly reduced upward on the stem. S. hydrophilus favors marshy, alkaline sites and can tolerate standing water.
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