Cirsium carolinianum
Cirsium arizonicum
Carolina or purple or soft or smallhead thistle, Carolina thistle, soft thistle
Arizona thistle
usually single, erect, glabrous to ± tomentose, sometimes sparsely villous with septate trichomes;
branches few, usually distal, ascending.
1–several, erect or ascending, glabrous to thinly arachnoid-tomentose with fine non-septate trichomes and/or villous with septate trichomes, sometimes ± glabrate;
branches 0–many, ascending.
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 oblong-elliptic, 3–40 × 1–13 cm, unlobed and spinulose to shallowly lobed or divided nearly to midvein, lobes few–many, ovate to linear-acuminate, often again lobed or divided, main spines 2–30 mm, abaxial faces green, glabrous to densely gray tomentose, sometimes midveins villous with septate trichomes, adaxial green, glabrous to gray-tomentose, sometimes glabrate;
basal sometimes present at flowering, unlobed to deeply spiny-lobed, winged-petiolate or sessile;
principal cauline sessile, well distributed, gradually diminished distally, bases sometimes decurrent as spiny wings to 2.5 cm or clasping;
distalmost sometimes ± bractlike.
slender, 1–15 cm (not overtopped by distal leaves).
0–15 cm.
narrowly ovoid to campanulate, 1.2–2 × 1.2–2 cm, thinly arachnoid-ciliate.
cylindric or ovoid to campanulate, 1.5–4 × 1–2.5 cm (body), loosely arachnoid or ± glabrous.
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.
pink to red, lavender, or purple (white), 25–31 mm, tubes 7–12.5 mm, throats 1.5–8.5 mm, lobes 10–17 mm;
style tips 1–4 mm.
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 7–9 series, imbricate, green or the inner reddish to rich reddish purple, ovate or lanceolate (outer) to linear (inner), margins of outer entire, abaxial faces often with narrow, inconspicuous glutinous ridge;
outer and mid bodies appressed, short, entire, apices spreading to ascending, inconspicuous to long, narrow, entire or minutely ciliolate, spines erect to reflexed (outer) to ascending (inner), slender to stout, cylindric or basally flattened, 1–30 mm;
apices of inner unarmed or with straight or flexuous spines, short, flat.
(1–)2–9(–many), in paniculiform arrays.
1–100+, erect, in corymbiform or paniculiform arrays.
light brown, 3–4 mm, apical collars yellowish, 0.5–1 mm;
pappi 12–14 mm.
brown, 3.5–7 mm, apical collars stramineous, 0.2–0.3 mm;
pappi 17–28 mm.
= 20, 22.
= 30, 32, 34.
Cirsium carolinianum
Cirsium arizonicum
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.)
Varieties 5 (5 in the flora).
The Cirsium arizonicum complex is widely distributed from the Sierra Nevada, White Mountains, and New York Mountains of eastern California across the mountains of the southern Great Basin and Colorado Plateau to the mountains of eastern Colorado, Arizona, and New Mexico. This group of plants comprises a series of intergrading races with intricately overlapping patterns of variation. For plants that I am treating as C. arizonicum (in the broad sense), F. Petrak (1917) recognized three species, one with a variety and two subspecies plus his unstated type subspecies and variety. R. J. Moore and C. Frankton (1974b) revised the complex, recognizing six species, three of them newly described, for the plants I treat as C. arizonicum plus C. turneri, which I do not include in C. arizonicum. P. L. Barlow-Irick (2002), in a work focused on statistical analyses of variation patterns, recognized six species also, but circumscribed very differently from those of Moore and Frankton. Two of the species proposed by Barlow-Irick have not been formally described.
I have wrestled with how to treat these plants since beginning my research for this treatment. After careful consideration of the complex patterns of variation among members of the C. arizonicum complex, I acknowledged the futility of trying to distinguish more than one species. Any character combinations that I or others have attempted to use to distinguish species break down hopelessly when enough specimens are examined. Instead I have chosen to recognize that in this complex, as in several others, the plants in question are a work of evolution in progress. Cirsium arizonicum is a rapidly evolving, only partially differentiated assemblage of races that have not reached the level of stability that is usually associated with the concept of species. Certainly there is much variation within the group that deserves a level of taxonomic recognition, or at least should be mentioned, but I think it much more prudent to recognize varieties–entities that may be expected to freely intergrade–rather than species. The geographic area where these plants occur, the highlands of the American Southwest, has had a turbulent history in the Quaternary with major shifts in climate, vegetation, and elevational zonation accompanying the vicissitudes of glacial and interglacial episodes. The complicated patterns of variation in C. arizonicum reflect both that history and the geographic and topographic complexity of the region.
Heads of Cirsium arizonicum are visited by hummingbirds as well as a variety of insects (P. L. Barlow-Irick 2002). Hummingbirds are the most common visitors, but hummingbirds and bees are both apparently effective pollinators in C. arizonicum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Corollas bright red or reddish pink | → 2 |
1. Corollas lavender to reddish purple | → 3 |
2. Leaves glabrous on both faces | var. rothrockii |
2. Leaves ± tomentose, at least on the abaxial faces | var. arizonicum |
3. Stems and abaxial leaf midveins villous to tomentose with septate trichomes; leaves conspicuously decurrent; leaves deeply divided, lobes many, narrow, closely spaced, each tipped by a very slender spine 5–12 mm; northeastern Arizona and northwestern New Mexico | var. chellyense |
3. Stems and abaxial leaf midveins glabrous to tomentose with fine, non-septate trichomes; septate trichomes usually absent; leaf divisions various | → 4 |
4. Principal marginal leaf spines 3–10 mm; New Mexico, northeastern Arizona, southeastern Utah, and southwestern Colorado | var. bipinnatum |
4. Principal marginal leaf spines 5–30 mm; southeastern California and southwestern Nevada | var. tenuisectum |
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