Cirsium altissimum
Cirsium drummondii
roadside thistle, tall thistle
Drummond's or dwarf or short-stem thistle, Drummond's thistle, dwarf thistle, short-stem thistle
single, erect, villous with septate trichomes, sometimes ± glabrate, sometimes distally thinly tomentose;
branches few–many, ascending.
erect, stout, fleshy, leafy, simple or distally branched, villous or tomentose with long, septate trichomes;
branches usually short, stout, ascending.
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-elliptic to oblanceolate, 15–30+ × 3–7 cm, usually shallowly to deeply pinnatifid, lobes ovate to broadly triangular, spreading, usually separated by broad U-shaped sinuses, spinose-dentate or coarsely lobed, main spines 2–5(–8) mm, slender, abaxial faces villous with septate trichomes, at least along veins, sometimes thinly arachnoid, adaxial villous with septate trichomes;
basal often present at flowering, spiny winged-petiolate;
principal cauline winged-petiolate or sessile, not much reduced distally;
distal reduced, similar to proximal, crowded around heads.
0–5 cm (leafy-bracted).
0–5(–10) cm, leafy-bracted.
ovoid to broadly cylindric or campanulate, (2–)2.5–3.5(–4) × (1.5–)2–3(–4) cm, thinly arachnoid.
broadly ovoid to hemispheric, 3.5–5 × 3.5–5 cm (appearing much wider and ± campanulate in pressed specimens), loosely arachnoid on phyllary margins or glabrate.
tips 4–6 mm.
pink to purple (white), 20–35 mm, tubes 10–16 mm, throats 5–12 mm, lobes 5–9 mm.
purple (white), 30–48 mm, tubes 17–30 mm, throats 6.5–11 mm, lobes 5–7 mm;
style tips 5–7 mm.
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 4–6 series, strongly imbricate, ovate or broadly lanceolate (outer) to lance-linear (inner), abaxial faces with ± narrow glutinous ridge;
outer and mid appressed, spines erect to ascending, 2–3 mm;
apices of mid and inner narrowed and scabrid-denticulate, innermost spineless, with expanded, flexuous, erose-denticulate tips.
1–many, in corymbiform or paniculiform arrays, (± elevated above principal cauline leaves), not subtended by ring of spiny bracts.
1–5(–9), borne singly or crowded in corymbiform arrays at tips of main stems, often closely subtended and overtopped by 1–several distal leaves.
tan to dark brown, 4–5.5 mm, apical collars stramineous, 0.5–1 mm;
pappi 12–24 mm.
stramineous to light brown, 3.5–5.5 mm, apical collar yellow, narrow;
pappi 30–42 mm.
= 18.
Cirsium altissimum
Cirsium drummondii
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.)
Cirsium drummondii is widely distributed across Canada from the Northwest Territories to British Columbia and Ontario. The name C. drummondii has been misapplied to a wide range of plants across the western United States that are now treated as one or another variety of the polymorphic C. scariosum. The only documented modern occurrences of C. drummondii in the United States are in the Black Hills of South Dakota and adjacent Wyoming. Specimens collected by Hall and Harbour (342) are the only ones of C. drummondii known from Colorado. Somewhat similar plants from northern Nevada are treated here as C. scariosum var. toiyabense. During Pleistocene glaciations the ancestors of C. drummondii undoubtedly occupied a more southerly distribution and very likely came into direct contact with populations of C. scariosum. The observed similarities between C. drummondii and C. scariosum var. toiyabense are probably a relict of that ancient contact.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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