Cirsium altissimum |
Cirsium cymosum |
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roadside thistle, tall thistle |
graygreen thistle, peregrine 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. | Biennials or perennials, 25–120 cm, pubescence a mixture of fine, non-septate arachnoid trichomes and coarser, septate trichomes, especially along stems and on midveins on abaxial leaf faces, usually ± loose and irregularly deciduous from leaves in age; taprooted. | ||||
Stems | single, erect, villous with septate trichomes, sometimes ± glabrate, sometimes distally thinly tomentose; branches few–many, ascending. |
usually 1, erect, ± gray-tomentose, sometimes villous with septate trichomes; branches 0–10+, usually arising in distal 1/2, ascending, usually reaching a ± common height. |
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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 linear-oblong to oblanceolate or elliptic, 10–30 × 3–7 cm, shallowly to deeply pinnatifid with 3–8 pairs of lobes, longer than 2 cm, lobes well separated, linear to triangular-ovate, dentate to lobed proximally, main spines slender, 2–7 mm, faces green to gray, thinly to densely arachnoid-tomentose with fine, non-septate trichomes, sometimes villous with septate trichomes along veins, usually ± loose and irregularly deciduous from leaves in age; basal often present at flowering, sessile or winged-petiolate; principal cauline mostly in proximal 1/2, winged-petiolate or sessile, bases narrowed, auriculate, veins often prominently raised on abaxial faces; distal sessile, auriculate-clasping or short-decurrent 1–10 mm, progressively reduced becoming bractlike, often unlobed or less deeply divided and sometimes spinier than proximal. |
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Peduncles | 0–5 cm (leafy-bracted). |
(0–)2–15 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. |
ovoid to hemispheric or campanulate, 2–3 × 1.5–3.5 cm, ± arachnoid-floccose, often glabrate. |
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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. |
creamy white to purplish, 20–31 mm, tubes 8–14 mm, throats 5.5–10 mm, lobes 6–7 mm; style tips 4–6 mm. |
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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 8–10 series, subequal to strongly imbricate, green, linear to lanceolate (outer) to linear (inner), entire, abaxial faces with inconspicuous to prominent glutinous ridge; outer and mid bodies loosely spreading to ascending or appressed, apices subappressed to ascending or spreading, flat, spines ascending to spreading, fine, 2–4 mm; apices of inner commonly flexuous or reflexed, narrow, flat, scarious. |
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Heads | 1–many, in corymbiform or paniculiform arrays, (± elevated above principal cauline leaves), not subtended by ring of spiny bracts. |
borne singly, terminal on main stem and branches, sometimes also in distal axils, erect, not subtended by well-developed leaves, collectively forming corymbiform or racemiform 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. |
tan to dark brown, 5–7.5 mm, apical collars not differentiated; pappi 16–25 mm. |
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2n | = 18. |
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Cirsium altissimum |
Cirsium cymosum |
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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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CA; ID; MT; NV; OR; WY
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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 2 (2 in the flora). Past floras have treated Cirsium cymosum and C. canovirens as separate species. In my examination of these plants across their combined ranges I realized that they are connected by numerous intermediates and that I could find no characters that consistently distinguish them. (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, p. 136. | ||||
Parent taxa | Asteraceae > tribe Cardueae > Cirsium | Asteraceae > tribe Cardueae > Cirsium | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Carduus altissimus, C. altissimum var. biltmoreanum, C. iowense | Carduus cymosus, C. botrys, C. triacanthum | ||||
Name authority | (Linnaeus) Sprengel: Syst. Veg. 3: 373. (1826) | (Greene) J. T. Howell: Amer. Midl. Naturalist 30: 37. (1943) | ||||
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