Cirsium palustre
Cirsium praeteriens
cirse ou chardon des marais, European Marsh thistle, European swamp or marsh thistle, European swamp thistle, marsh thistle
lost or Palo Alto thistle, lost thistle, Palo Alto thistle
single, erect, villous to tomentose with jointed trichomes, distally tomentose with fine, unbranched trichomes;
branches 0–few, ascending, (short).
stout, erect, loosely arachnoid with fine trichomes and villous with jointed trichomes; branching unknown.
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 elliptic to oblanceolate, 15–30+ × 6–8+ cm, divided halfway or more to midveins, lobes linear-lanceolate, rigidly spreading, entire or trifid, acuminate, main spines stout, 5–15 mm, abaxial faces tomentose with fine, non-septate trichomes, villous along major veins with septate trichomes, adaxial glabrescent or sparsely tomentose, villous along veins;
basal not observed;
cauline well distributed, distally not much reduced, sessile, bases clasping, not decurrent.
0–1 cm.
0–1 cm.
ovoid to campanulate, 1–1.5 × 0.8–1.3 cm, thinly cobwebby tomentose with fine unbranched trichomes.
hemispheric to broadly campanulate, 3–4 × 4–5+ cm, arachnoid.
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.
white, 30–33 mm, tubes 16 mm, throats 9–12 mm, lobes 5.5–9 mm;
style tips 6 mm.
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 6–8 series, narrowly lanceolate to linear, outer subequal, rigidly spreading, spines 5–10 mm, inner ± imbricate, bodies appressed, glutinous ridge absent, apices spreading, margins spinulose or scabrid, apices of mid and inner flattened, spineless, scabrid.
few–many in dense clusters at branch tips.
1–5, terminal and in distal axils in spiciform arrays.
tan to stramineous, 2.5–3.5 mm, apical collars 0.1–0.2 mm, shiny;
pappi 9–11 mm.
light brown, 6 mm, collars also light brown, ca. 0.75 mm;
pappi 25–33 mm.
= 34.
Cirsium palustre
Cirsium praeteriens
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.)
Of conservation concern.
Cirsium praeteriens is known only from Santa Clara County, where J. W. Congdon collected it in Palo Alto in 1897 and 1901. It is presumed extinct.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
BC
Go Botany
MI Flora
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
CA
