Cirsium altissimum |
Cirsium eatonii |
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roadside thistle, tall thistle |
Eaton's thistle, mountaintop thistle, Peck's thistle, Steens Mountain thistle |
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Habit | Biennials or short-lived monocarpic perennials, (50–)100–300(–400) cm; taproots and often a cluster of coarse fibrous roots, roots without tuberlike enlargements. | Perennials, 10–150 cm; taprooted caudices. | ||||||||||||||||||||||||||||
Stems | single, erect, villous with septate trichomes, sometimes ± glabrate, sometimes distally thinly tomentose; branches few–many, ascending. |
1–several, (fleshy), erect or ascending, simple to sparingly branched in distal 1/2, sometimes openly branched, glabrous to villous or tomentose with septate trichomes, sometimes ± glabrate; branches on distal stems 0–many, ascending. |
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Leaves | blades oblanceolate to elliptic or ovate, 10–40 × 1–13 cm, margins flat, finely spiny-toothed and otherwise undivided to coarsely toothed or shallowly pinnatifid, lobes broadly triangular, main spines 1–5 mm, abaxial faces white-tomentose, adaxial faces green, glabrate to villous with septate trichomes; basal usually absent at flowering, winged-petiolate, bases tapered; principal cauline well distributed, gradually reduced, bases narrowed, sometimes weakly clasping; distal cauline well developed. |
blades oblong, 10–30 × 1–5 cm, margins usually strongly undulate, unlobed and spiny-dentate or shallowly to deeply pinnatifid with 10–20 pairs of lobes, teeth or lobes closely spaced, often overlapping, lance-oblong to broadly triangular, deeply 3-lobed, ± spiny-dentate, main spines 2–12 mm, abaxial faces glabrous or villous with septate trichomes along midveins to densely arachnoid-tomentose, adaxial glabrous or villous with septate trichomes along midveins; basal often present at flowering, spiny winged-petiolate or sessile; principal cauline many, well distributed, proximally ± winged-petiolate, distally sessile, gradually reduced; distal not much reduced, often closely subtending heads. |
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Peduncles | 0–5 cm (leafy-bracted). |
0–14+ cm. |
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Involucres | ovoid to broadly cylindric or campanulate, (2–)2.5–3.5(–4) × (1.5–)2–3(–4) cm, thinly arachnoid. |
green or suffused with dark purple, broadly ovoid to campanulate, 2–5 × 1.5–5 cm (appearing wider when pressed), loosely to densely villous or tomentose with septate trichomes and/or arachnoid-tomentose with finer, non-septate trichomes. |
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Style | tips 4–6 mm. |
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Corollas | pink to purple (white), 20–35 mm, tubes 10–16 mm, throats 5–12 mm, lobes 5–9 mm. |
ochroleucous or yellow to lavender, pink, or purple, 15–35 mm, tubes 3.5–10 mm, throats 5–14 mm, lobes (linear), 4–12.5 mm; style tips 3–6 mm, conspicuously exserted beyond corolla lobes. |
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Phyllaries | in 10–20 series, strongly imbricate, greenish with subapical darker central zone, ovate (outer) to lanceolate (inner), abaxial faces with a narrow glutinous ridge (milky when fresh, dark when dry), outer and middle entire, bodies appressed, spines slender, abruptly spreading, 3–4 mm; apices of inner phyllaries spreading, narrow, flattened, entire, spines spreading, slender, 3–4 mm; apices of inner phyllaries spreading, narrow, flattened, ± dilated, ± erose or finely serrulate. |
in 4–5 series, subequal, bases short-appressed, abaxial faces without or with very narrow glutinous ridge, apices usually stiffly ascending to spreading, linear-acicular, tapering to spines 7–35 mm; outer usually pinnately spiny, sometimes entire; apices of inner straight, plane or spine-tipped. |
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Heads | 1–many, in corymbiform or paniculiform arrays, (± elevated above principal cauline leaves), not subtended by ring of spiny bracts. |
1–many, erect or nodding, closely subtended by spiny-fringed bracts, usually sessile or short-pedunculate and crowded in subcapitate, spiciform, or racemiform (less commonly in openly branched) arrays. |
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Cypselae | tan to dark brown, 4–5.5 mm, apical collars stramineous, 0.5–1 mm; pappi 12–24 mm. |
dark brown, 5.5–7 mm, apical collars stramineous or not differentiated; pappi 12–25 mm. |
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2n | = 18. |
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Cirsium altissimum |
Cirsium eatonii |
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Phenology | Flowering summer–fall (Jun–Oct). | |||||||||||||||||||||||||||||
Habitat | Prairies, woodlands, disturbed sites, often in damp soil | |||||||||||||||||||||||||||||
Elevation | 50–700 m (200–2300 ft) | |||||||||||||||||||||||||||||
Distribution |
AL; AR; DC; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; MI; MN; MO; MS; NC; ND; NE; NY; OH; OK; PA; SC; SD; TN; TX; WI; WV
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CO; ID; MT; NM; NV; OR; UT; WY; Rocky Mountains and high peaks of Great Basin desert region
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Discussion | Plants of Cirsium altissimum ranging from southern Minnesota to Texas often have more deeply divided leaves than do populations in other portions of the species’ range. Some botanists (e.g., R. J. Moore and C. Frankton 1969; D. S. Correll and M. C. Johnston 1970) have treated those plants as C. iowense. Others (e.g., R. E. Brooks 1986; H. A. Gleason and A. Cronquist 1991; G. B. Ownbey and T. Morley 1991) have treated them as C. altissimum. Still others considered them to be derivatives of hybridization between C. altissimum and C. discolor (J. T. Kartesz and C. A. Meacham 1999) and treated them as C. ×iowense. Indeed the existence of these plants blurs the distinction between C. altissimum and C. discolor, and herbarium specimens are often difficult to assign. Natural hybrids between Cirsium altissimum and C. discolor are well documented (R. A. Davidson 1963; G. B. Ownbey and Hsi Y.-T. 1963; Ownbey 1964; S. Dabydeen 1997). Ownbey and Dabydeen both reported that apparent F1 hybrids between the two species have low seed set in comparison with the parental taxa. W. L. Bloom (1977) reported that the chromosomes of the two species differ by several rearareaments. Dabydeen reported a count of 2n = 19 with multiple meiotic irregularities for an apparent F1 hybrid. However, the presence of numerous individuals and populations seemingly intermediate between C. altissimum and C. discolor indicates that although F1 hybrids have low fertility, long-term processes may have stabilized hybrid derivatives of higher fertility. Ownbey and Hsi reported mitotic counts of 2n = 18 and 20 from a population that they treated as C. altissimum. In their discussion they noted that their plants represented “the segregate called C. iowense” and had been collected a short distance from that taxon’s type locality. R. J. Moore and C. Frankton (1969) reported a chromosome number of 2n = 18 for a plant from Texas that they considered to be C. iowense. Further investigation of morphologic variation, chromosome number, meiotic behavior, and fertility is needed of populations named as C. iowense to determine how those plants should be treated. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Varieties 7 (7 in the flora). Cirsium eatonii is a polymorphic species widely distributed in a high elevation archipelago across the central Rocky Mountains and the Intermountain Region. During Pleistocene glacial episodes, the progenitors of this species complex undoubtedly occupied lower elevation sites and likely had more contiguous populations. Post-glacial isolation of these populations in allopatric high elevation sites has allowed them to differentiate to a greater or lesser extent. Prehistoric or recent introgressive hybridization with other thistle species probably has contributed to the diversification of the complex (R. J. Moore and C. Frankton 1965). Several of the races recognized here as varieties have been treated in the past as species (e.g., C. clokeyi, C. peckii). Their current geographic isolation and more or less distinctive features might support such recognition, but application of this approach across the complex would result in a proliferation of microspecies. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 19, p. 111. | FNA vol. 19. | ||||||||||||||||||||||||||||
Parent taxa | Asteraceae > tribe Cardueae > Cirsium | Asteraceae > tribe Cardueae > Cirsium | ||||||||||||||||||||||||||||
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Subordinate taxa | ||||||||||||||||||||||||||||||
Synonyms | Carduus altissimus, C. altissimum var. biltmoreanum, C. iowense | Cnicus eatonii | ||||||||||||||||||||||||||||
Name authority | (Linnaeus) Sprengel: Syst. Veg. 3: 373. (1826) | (A. Gray) B. L. Robinson: Rhodora 13: 240. (1911) | ||||||||||||||||||||||||||||
Web links |