Cirsium carolinianum |
Cirsium palustre |
|
---|---|---|
Carolina or purple or soft or smallhead thistle, Carolina thistle, soft thistle |
cirse ou chardon des marais, European Marsh thistle, European swamp or marsh thistle, European swamp thistle, marsh thistle |
|
Habit | Biennials, 50–180 cm; taproots short with many slender, fibrous lateral roots. | Biennials or monocarpic perennials, 30–200(–300) cm; clusters of fibrous roots. |
Stems | usually single, erect, glabrous to ± tomentose, sometimes sparsely villous with septate trichomes; branches few, usually distal, ascending. |
single, erect, villous to tomentose with jointed trichomes, distally tomentose with fine, unbranched trichomes; branches 0–few, ascending, (short). |
Leaves | blades linear to oblanceolate or elliptic, 10–30 × 1–5 cm, unlobed and spinulose to irregularly dentate or pinnatifid, lobes narrowly to broadly triangular, sometimes coarsely toothed or lobed toward base, acuminate, main spines slender, 1–5 mm, abaxial faces gray-tomentose, adaxial glabrous or sparsely villous with septate trichomes; basal often present at flowering, petioles slender, winged, bases long-tapered; principal cauline relatively few (10–25), petiolate or distal sessile, mostly restricted to proximal 1/2 of stems, progressively reduced distally, bases tapered, not decurrent; distal cauline widely separated, linear to narrowly elliptic, reduced, becoming ± bractlike, merely spinulose to irregularly dentate or shallowly lobed. |
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. |
Peduncles | slender, 1–15 cm (not overtopped by distal leaves). |
0–1 cm. |
Involucres | narrowly ovoid to campanulate, 1.2–2 × 1.2–2 cm, thinly arachnoid-ciliate. |
ovoid to campanulate, 1–1.5 × 0.8–1.3 cm, thinly cobwebby tomentose with fine unbranched trichomes. |
Corollas | pink-purple (white), 15–20 mm, tubes 5–9 mm, throats 5–7 mm (noticeably wider than tubes), lobes 4–5 mm; style tips 4 mm. |
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. |
Phyllaries | in 7–10 series, imbricate, green, linear to lanceolate (outer) or linear to linear-lanceolate (inner), abaxial faces with narrow, glutinous ridge; outer and middle ascending to appressed, bodies entire, apices widely spreading (at least the outer), spines ascending to spreading (at least the outer), slender, 1–4 mm; apices of inner phyllaries flat, often twisted, acuminate. |
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. |
Heads | (1–)2–9(–many), in paniculiform arrays. |
few–many in dense clusters at branch tips. |
Cypselae | light brown, 3–4 mm, apical collars yellowish, 0.5–1 mm; pappi 12–14 mm. |
tan to stramineous, 2.5–3.5 mm, apical collars 0.1–0.2 mm, shiny; pappi 9–11 mm. |
2n | = 20, 22. |
= 34. |
Cirsium carolinianum |
Cirsium palustre |
|
Phenology | Flowering spring–summer (Apr–Jul). | Flowering summer (Jul–Aug). |
Habitat | Wooded areas, openings, fields, roadsides | Marshes, wet forests |
Elevation | 50–300 m (200–1000 ft) | 10–800 m (0–2600 ft) |
Distribution |
AL; AR; GA; IL; IN; KY; LA; MO; MS; NC; OH; OK; SC; TN; TX
|
MA; MI; NH; NY; WI; BC; NF; NS; ON; QC; SPM; Europe [Introduced in North America]
|
Discussion | Cirsium carolinianum is widely distributed in the southeastern United States: on the Gulf coastal plain from Texas to Alabama north through the Ouachita and Ozark highlands to southeastern Missouri; in the Ohio River Valley from southernmost Illinois to southern Ohio and northern Kentucky; and in the southern Appalachians and Piedmont from Alabama and Tennessee to southern Virginia. Cirsium carolinianum, though widespread, is a taxon of conservation concern over part of its range. The replacement of open woods by dense forests brought about by fire suppression has greatly reduced available habitat. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 19, p. 118. | FNA vol. 19, p. 110. |
Parent taxa | Asteraceae > tribe Cardueae > Cirsium | Asteraceae > tribe Cardueae > Cirsium |
Sibling taxa | ||
Synonyms | Carduus carolinianus, C. flaccidum | Carduus palustris |
Name authority | (Walter) Fernald & B. G. Schubert: Rhodora 50: 229. (1948) | (Linnaeus) Scopoli: Fl. Carniol. ed. 2, 2: 128. (1772) |
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