Cirsium vulgare |
Cirsium canescens |
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bull or common or spear thistle, bull thistle, chardon vulgaire ou lancéolé, common thistle, gros chardon, piqueux, spear thistle |
Platte thistle, prairie thistle |
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Habit | Biennials, 30–200(–300) cm; taproots. | Biennials or monocarpic perennials, 20–100 cm; taproots long. |
Stems | 1–many, erect or ascending, branches few–many, ascending, villous with septate trichomes. |
usually 1, erect, ± densely gray-tomentose with fine, non-septate trichomes; branches 0 or few, usually above middle in distal 1/2, ascending. |
Leaves | blades oblong-lanceolate to obovate, 15–40 × 6–15 cm, margins plane or revolute, coarsely 1–2-pinnatifid with rigidly divergent lobes, sometimes merely spinose-dentate, lobes triangular to lanceolate, entire to spiny-dentate, main spines 2–10 mm, abaxial faces gray-tomentose, villous with septate trichomes along veins, adaxial green, covered with short appressed bristlelike spines, sometimes tomentose when young; basal present or absent at flowering, petioles winged, bases tapered; principal cauline winged-petiolate, mid and distal becoming sessile, well distributed or not, progressively reduced distally, at least distal decurrent as long spiny wings; distal cauline often more deeply lobed than proximal, main lobes rigidly spiny, margins spinulose, otherwise entire. |
blades oblong to elliptic or obovate, 10–25(–40) × 2–6(–12) cm, coarsely dentate or shallowly lobed to deeply pinnatifid, lobes well separated, triangular to linear or oblong, often revolute-margined, ascending to spreading, spinulose to spinose-dentate, main spines 2–3(–10) mm, faces gray-tomentose, more densely abaxially, sometimes glabrate adaxially; basal usually present at flowering, winged-petiolate; principal cauline progressively reduced distally, bases decurrent as spiny wings 1–5 cm, sometimes with expanded auricles; distal cauline usually much reduced, less lobed. |
Peduncles | 1–6 cm. |
0–10 cm. |
Involucres | hemispheric to campanulate, 3–4 × 2–4 cm, loosely arachnoid-tomentose. |
hemispheric to broadly campanulate, usually truncate or indented at base, 3–4 × 2.5–4 cm in first-formed heads, often smaller (1.5–2 cm) in later ones, loosely arachnoid on phyllary margins or glabrate. |
Corollas | purple (rarely white), 25–35 mm, tubes 18–25 mm, throats 5–6 mm, lobes 5–7 mm; style tips 3.5–6 mm. |
dull white or lavender-tinged, 20–35 mm, tubes 10–17 mm, throats 6–11 mm, lobes 4–9 mm; style tips 5–8 mm. |
Phyllaries | in 10–12 series, strongly imbricate, linear-lanceolate (outer) to linear (inner), outer and middle appressed, (bases stramineous), margins entire, abaxial faces without glutinous ridge, apices radiating, greenish, spines 2–5 mm; apices of inner phyllaries flat, serrulate to minutely erose. |
in 6–9 series, imbricate, ovate-lanceolate (outer) to linear-lanceolate (inner), abaxial faces with prominent glutinous ridge; bodies of outer and middle appressed, acute, spines ascending to spreading, 2–4(–8) mm; apices of inner expanded and flat, often twisted, scabrid-margined, and erose, spineless. |
Heads | few–many in corymbiform or paniculiform arrays. |
1–10+, terminal on branches or in distal axils, in openly corymbiform to racemiform arrays. |
Cypselae | light brown with darker streaks, 3–4.5 mm, apical collar not differentiated; pappi 20–30 mm. |
light brown, 5–7 mm, sometimes with darker streaks, apical collar very narrow, lighter colored; pappi 18–30 mm, usually noticeably shorter than corolla. |
2n | = 68. |
= 34, 36. |
Cirsium vulgare |
Cirsium canescens |
|
Phenology | Flowering mostly summer (Jun–Sep), year round in areas with mild climates. | Flowering spring–summer (May–Aug). |
Habitat | Invasive weed of disturbed sites, pastures, meadows, forest openings, roadsides | Sandy or gravelly soils in short-grass prairie, often in disturbed areas, mountain meadows, grassy slopes in montane coniferous forests |
Elevation | 0–2200 m (0–7200 ft) | 1100–3800 m (3600–12500 ft) |
Distribution |
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NF; NS; ON; PE; QC; SK; SPM; Eurasia [Introduced in North America]
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CA; CO; MO; MT; NE; NV; SD; WY
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Discussion | Native to Eurasia, Cirsium vulgare is the only thistle in North America with bristlelike spines borne on the adaxial leaf faces. These structures are variously described in the literature as trichomes (“spreading hirsute,” “scabrous-hispid,” “coarsely hispid,” “rigid, rather pungent setae,” “prickly-hairy”), prickles, or spines (“setose-spinulose,” “appressed and dense spines”). My examination of cleared leaves of C. vulgare indicated that these structures are not epidermal outgrowths (trichomes or prickles) but emerge from fine veinlets within the tissues of the leaf. As such, they are properly treated as spines. Bull thistle is a noxious weed that has invaded disturbed habitats across the continent. Distasteful to livestock, it can increase in heavily grazed pastures. It occurs in a wide variety of habitats. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Cirsium canescens grows in the northern Great Plains from eastern Montana and Wyoming to eastern Colorado and Nebraska; an upland race occurs in the Rocky Mountains of eastern Colorado. It has been reported from Iowa, North Dakota, and Ohio; I have not seen specimens from those states. It is adventive in northeastern California. Cirsium canescens hybridizes locally with C. scariosum and C. parryi. Further investigations may reveal that high-elevation forms of C. canescens from the mountains of Colorado are worthy of taxonomic recognition. These plants flower later than the low elevation forms of the Great Plains and occur in rather different ecologic conditions, but I have found no features that readily distinguish them. Populations of C. canescens have been particularly affected by the seedhead weevil Rhinocyllus conicus, introduced to North America to control weedy species of Carduus (S. M. Louda et al. 1997; Louda 1998). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 19, p. 109. | FNA vol. 19, p. 122. |
Parent taxa | Asteraceae > tribe Cardueae > Cirsium | Asteraceae > tribe Cardueae > Cirsium |
Sibling taxa | ||
Synonyms | Carduus vulgaris, Carduus lanceolatus | C. nebraskense, C. plattense, C. nelsonii |
Name authority | (Savi) Tenore: Fl. Napol. 5: 209. (1835) | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 420. (1841) |
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