Cirsium remotifolium
Cirsium altissimum
few-leaf thistle, mountain thistle, Pacific fringe thistle, remote-leaf thistle, weak thistle
roadside thistle, tall 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.
single, erect, villous with septate trichomes, sometimes ± glabrate, sometimes distally thinly tomentose;
branches few–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 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.
(0–)2–15 cm.
0–5 cm (leafy-bracted).
ovoid to hemispheric or campanulate, 1.5–2.5 × 1.5–3.5 cm, glabrous to arachnoid-floccose.
ovoid to broadly cylindric or campanulate, (2–)2.5–3.5(–4) × (1.5–)2–3(–4) cm, thinly arachnoid.
tips 4–6 mm.
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 purple (white), 20–35 mm, tubes 10–16 mm, throats 5–12 mm, lobes 5–9 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 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.
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–many, in corymbiform or paniculiform arrays, (± elevated above principal cauline leaves), not subtended by ring of spiny bracts.
tan to dark brown, 4.5–5.5 mm, apical collars differentiated or not;
pappi 13–23 mm.
tan to dark brown, 4–5.5 mm, apical collars stramineous, 0.5–1 mm;
pappi 12–24 mm.
= 32.
= 18.
Cirsium remotifolium
Cirsium altissimum
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.)
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.)
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 |
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