Cirsium palustre |
Cirsium clavatum |
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cirse ou chardon des marais, European Marsh thistle, European swamp or marsh thistle, European swamp thistle, marsh thistle |
Fish Lake thistle, fringe thistle |
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Habit | Biennials or monocarpic perennials, 30–200(–300) cm; clusters of fibrous roots. | Biennials or monocarpic or polycarpic perennials, 20–100 cm; taproots sometimes with branched caudices. | ||||||||
Stems | single, erect, villous to tomentose with jointed trichomes, distally tomentose with fine, unbranched trichomes; branches 0–few, ascending, (short). |
1–several, erect or ascending, glabrous or thinly arachnoid-tomentose; branches 0–10+, slender, usually arising in distal 1/2, ascending. |
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Leaves | blades narrowly elliptic to oblanceolate, 15–30+ × 3–10 cm, margins shallowly to very deeply pinnatifid, narrow lobes separated by broad sinuses, spiny-dentate to lobed, main spines 2–6 mm, abaxial villous to tomentose with jointed trichomes, sometimes also thinly tomentose with fine unbranched trichomes, adaxial faces villous with septate trichomes or glabrate; basal often present at flowering, petioles spiny-winged, bases tapered; cauline many, sessile, gradually reduced and becoming widely spaced above, bases long-decurrent with prominently spiny wings; distal cauline deeply pinnatifid with few-toothed spine-tipped lobes. |
blades oblong to oblanceolate or elliptic, 5–40 × 3–11 cm, unlobed and merely spinulose-dentate or more commonly regularly deeply pinnatifid, lobes well separated to crowded, linear to triangular-ovate, ascending-spreading to retrorse, merely spinulose to coarsely dentate or proximally few-lobed, main spines 2–5(–7) mm, slender, abaxial faces green to gray, glabrous or thinly to densely arachnoid-tomentose, sometimes glabrate, often villous with septate trichomes along veins, adaxial green, glabrous; basal usually present at flowering, sessile or petiolate; principal cauline well distributed, proximal usually winged-petiolate, mid sessile, decurrent as spiny wings 1–3 cm; distal cauline ± reduced. |
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Peduncles | 0–1 cm. |
0–30 cm. |
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Involucres | ovoid to campanulate, 1–1.5 × 0.8–1.3 cm, thinly cobwebby tomentose with fine unbranched trichomes. |
ovoid to campanulate, 1.5–3 × 1–3 cm, glabrous to thinly arachnoid-tomentose and/or villous-ciliate, with long septate trichomes connecting adjacent phyllaries. |
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Corollas | lavender to purple (white), 11–13 mm, tubes 5–7 mm, throats 2–3 mm, lobes 3–4.5 mm; style tips 1.5–2 mm. |
creamy white to pale pinkish, 16–20 mm, tubes 6.5–9 mm, throats 4–7.5 mm, lobes 4–6 mm; style tips 3.5–5 mm. |
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Phyllaries | in 5–7 series, strongly imbricate, greenish, or with purplish tinge, lanceolate to ovate (outer) or linear-lanceolate (inner), margins thinly arachnoid-ciliate, abaxial faces with narrow glutinous ridge, outer and middle appressed, entire, apices acute, mucronate or spines erect or spreading, weak, 0.3–1 mm; apices of inner phyllaries purplish, linear-attenuate, scarious, flat. |
in 5–6 series, imbricate or subequal, outer green or with maroon to dark brown subapical patch or appendage, linear to ovate, abaxial faces with narrow glutinous ridge that may be concealed by trichomes; outer and middle with bases appressed, apical appendages erect or ascending, ovate to linear-lanceolate or acicular, entire or spinulose to broadly expanded, scarious, and erose-dentate, apical appendages, spines erect or ascending, 1–5 mm, ± flattened; apices of inner sometimes flexuous or reflexed, narrow, flat, entire or ± expanded, scarious and lacerate-dentate. |
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Heads | few–many in dense clusters at branch tips. |
few–many, borne singly or clustered in corymbiform, paniculiform, or racemiform arrays at tips of main stem and branches, sometimes also in distal axils not closely subtended by clustered leafy bracts. |
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Cypselae | tan to stramineous, 2.5–3.5 mm, apical collars 0.1–0.2 mm, shiny; pappi 9–11 mm. |
tan to dark brown, 5–6 mm, apical collars not or scarcely differentiated; pappi 14–16 mm. |
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2n | = 34. |
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Cirsium palustre |
Cirsium clavatum |
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Phenology | Flowering summer (Jul–Aug). | |||||||||
Habitat | Marshes, wet forests | |||||||||
Elevation | 10–800 m (0–2600 ft) | |||||||||
Distribution |
MA; MI; NH; NY; WI; BC; NF; NS; ON; QC; SPM; Europe [Introduced in North America]
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CO; UT; WY; Central Rocky Mountains
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Discussion | Cirsium palustre is a noxious weed, native to Europe, that invasively spreads through wetland communities, forming impenetrable spiny stands as it displaces native species. The range of this pernicious weed in North America is rapidly expanding. It has the potential to spread into boreal forest areas across the continent; in Europe it grows nearly to the Arctic Circle. The rapid spread of C. palustre in Michigan (E. G. Voss 1972–1996, vol. 3) is indicative of its invasiveness. Spontaneous hybrids between C. palustre and C. arvense have been reported from England and other European countries (W. A. Sledge 1975) and can be expected wherever these species grow together in North America. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Varieties 3 (3 in the flora). Cirsium clavatum is a polymorphic and variable species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 19, p. 110. | FNA vol. 19, p. 126. | ||||||||
Parent taxa | Asteraceae > tribe Cardueae > Cirsium | Asteraceae > tribe Cardueae > Cirsium | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Synonyms | Carduus palustris | Cnicus clavatus | ||||||||
Name authority | (Linnaeus) Scopoli: Fl. Carniol. ed. 2, 2: 128. (1772) | (M. E. Jones) Petrak: Beih. Bot. Centralbl. 35(2): 310. (1917) | ||||||||
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