Cirsium remotifolium
Cirsium arizonicum
few-leaf thistle, mountain thistle, Pacific fringe thistle, remote-leaf thistle, weak thistle
Arizona thistle
usually 1, erect, finely arachnoid-tomentose, sometimes villous with septate trichomes below nodes;
branches 0–10+, slender, usually arising in distal 1/2, 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-oblong to oblanceolate or elliptic, 7–30 × 1–15 cm, unlobed and spinulose to dentate or shallowly to deeply pinnatifid, lobes well separated, linear to triangular-ovate, dentate to deeply lobed, main spines 2–5 mm, slender, abaxial faces green to gray, thinly to densely arachnoid-tomentose, sometimes glabrate, sometimes villous with septate trichomes along veins, adaxial green, glabrous;
basal sometimes present at flowering, sessile or winged-petiolate;
principal cauline mostly in proximal 1/2, winged-petiolate or sessile, bases narrowed, sometimes auriculate;
distal well separated, progressively reduced, becoming bractlike, often unlobed or less deeply divided than the proximal, sometimes spinier than proximal, bases often distally expanded and auriculate-clasping.
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.
(0–)2–15 cm.
0–15 cm.
ovoid to hemispheric or campanulate, 1.5–2.5 × 1.5–3.5 cm, glabrous to arachnoid-floccose.
cylindric or ovoid to campanulate, 1.5–4 × 1–2.5 cm (body), loosely arachnoid or ± glabrous.
creamy white to purple, 18–28 mm, tubes 7–12 mm, throats 5–12 mm, lobes 3.5–7 mm, style tips 4–6 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 6–8 series, subequal to strongly imbricate, green, linear to obovate (outer) to linear (inner), abaxial faces with inconspicuous glutinous ridge;
outer and middle bases appressed, margins entire to spinulose-dentate or broad, scarious, lacerate-dentate, spines absent or ascending to spreading, 1–2 mm;
apices of inner sometimes flexuous or reflexed, narrow, flat, entire or expanded, scarious, and lacerate-dentate.
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.
few–many, borne singly or in openly branched in corymbiform, racemiform, or paniculiform arrays on main stem and branches, sometimes also in distal axils, not closely subtended by clustered leaf bracts.
1–100+, erect, in corymbiform or paniculiform arrays.
tan to dark brown, 4.5–5.5 mm, apical collars differentiated or not;
pappi 13–23 mm.
brown, 3.5–7 mm, apical collars stramineous, 0.2–0.3 mm;
pappi 17–28 mm.
= 32.
= 30, 32, 34.
Cirsium remotifolium
Cirsium arizonicum
Varieties 3 (3 in the flora).
Cirsium remotifolium occurs from the Coast Ranges and valleys of the Pacific Northwest to the western slopes of the Cascade and Klamath ranges, south in the California North Coast Ranges to the San Francisco Bay region. It is closely related to the C. clavatum complex of the Rocky Mountains region. Both have a similar growth habit and some forms variably express the character of broadly scarious, lacerate-toothed phyllary margins. Gray, in naming Cnicus carlinoides var. americanus, included as syntypes both California and Colorado specimens. F. Petrak (1917) treated both the West Coast plants and those of the Rocky Mountains as Cirsium subsect. Americana, recognizing C. remotifolium with several infraspecific taxa plus two other species, C. callilepis and C. amblylepis from the West Coast, and four additional species from the Rocky Mountains. A. Cronquist (1955) rejected Petrak’s subspecies, treating C. remotifolium in a restricted sense, limited to plants of Washington and Oregon without dilated phyllary tips, and circumscribed C. centaureae broadly to include the Rocky Mountains and West Coast plants with dilated phyllary tips. Because of the frequent presence of dilated phyllary tips in C. remotifolium in the restricted sense, Cronquist acknowledged the likelihood of past introgression with C. centaureae in the broad sense.
J. T. Howell (1960b) recognized three species: Cirsium remotifolium, C. acanthodontum, and C. callilepis, the latter with four varieties collectively corresponding to the West Coast representatives of C. centaureae (in the sense of Cronquist). Because of the great similarity of the various West Coast plants and their intergradation, I see no value in recognizing two or more species.
The West Coast and Rocky Mountains plants are clearly related, but are separated by the Great Basin region and there is little chance of current genetic interchange. As is often the case with American Cirsium, genetic enrichment from past hybridization with other nearby species within their respective areas has likely been fertile ground for evolutionary diversification. Different species have contributed genes in the Pacific states and in the Rockies. I have chosen to recognize two geographically-based species complexes, each with intergrading races here treated as varieties. I treat the West Coast plants as C. remotifolium and the Rocky Mountains plants as C. clavatum.
(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. Phyllary margins ciliate with tiny spreading to recurved spines | var. rivulare |
1. Phyllary margins unappendaged or dilated, scarious, and ± lacerate-toothed | → 2 |
2. Phyllaries narrowly oblong or linear, often ± subequal, all or most without scarious-dilated margins | var. remotifolium |
2. Phyllaries oblong to obovate, often strongly graduated, most or all with dilated, scarious, erose to lacerate-dentate margins | var. odontolepis |
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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