Cirsium hookerianum |
Cirsium engelmannii |
|
---|---|---|
Hooker's thistle, white thistle |
blackland thistle, Engelmann's thistle |
|
Habit | Biennials or monocarpic (sometimes polycarpic?) perennials, 20–150 cm; taprooted. | Biennials or monocarpic perennials, 40–200 cm; taproots and clusters of coarse fibrous roots that often have tuberlike thickenings. |
Stems | usually 1 and erect, less commonly several and ascending, simple to sparingly short-branched in distal 1/2, variably villous with jointed trichomes, and/or finely arachnoid, or ± glabrate; branches on distal stems 0–many, short, ascending. |
single, erect, often branched above middle, thinly arachnoid-tomentose, ± glabrate; branches few, ascending. |
Leaves | blades linear-oblong to elliptic, 5–25 × 1–8 cm, subentire to coarsely dentate or deeply pinnatifid, lobes lance-oblong to broadly triangular, spinulose to spiny-dentate or shallowly lobed, main spines 2–10 mm, abaxial faces usually ± densely gray- or white-tomentose with felted arachnoid trichomes, ± villous to tomentose along major veins with septate trichomes, sometimes glabrous or glabrate, adaxial ± green, glabrous to thinly arachnoid, often ± villous or tomentose with septate trichomes; basal often present at flowering, spiny winged-petiolate or sessile; principal cauline well distributed, proximally winged-petiolate, distally sessile, gradually reduced, bases sometimes short-decurrent; distal ± reduced, often narrower than proximal, sometimes with non-pigmented bases, sometimes pectinately spiny. |
blades elliptic or ovate, 5–20 × 1–10 cm, usually deeply pinnatifid, lobes narrowly to broadly triangular, sinuses broad, rounded (basal and distal cauline sometimes less divided, lobes linear-lanceolate), margins revolute, spreading, entire or spinulose to remotely few-toothed or sharply lobed, main spines slender, 1–5 mm, abaxial faces white-tomentose, adaxial green, villous with septate trichomes or glabrate; basal usually absent at flowering, winged-petiolate, bases tapered; principal cauline well distributed, gradually reduced, bases narrowed, sometimes weakly clasping; distal reduced, widely separated, distalmost bractlike. |
Peduncles | 0–8+ cm. |
2–20+ cm, essentially naked with much reduced bracts. |
Involucres | (green or often purplish), broadly ovoid, 2–3.3 × 1.5–4 cm, loosely to densely villous with septate trichomes to tomentose and/or arachnoid. |
ovoid to broadly cylindric or campanulate, 2.5–3.5 × 2–3 cm, thinly arachnoid. |
Corollas | white, ochroleucous, or occasionally pink, 20–28 mm, tubes 10–13 mm, throats 6.5–9 mm, lobes 5–7 mm; style tips 3–5.5 mm. |
pink to purple (white), 32–38 mm, tubes 15–20 mm, throats 6–9 mm, lobes 8–11 mm; style tips 5–6 mm. |
Phyllaries | in 4–8 series, imbricate to subequal, bases short-appressed, entire, abaxial faces with or without narrow glutinous ridge, apices stiffly spreading to ascending, linear, long, plane, spines straight, slender, 3–5 mm; apices of inner flexuous, sometimes expanded and erose. |
in 10–12 series, strongly imbricate, greenish with subapical darker central zone, ovate (outer) to lanceolate (inner), abaxial faces with narrow glutinous ridge; outer and middle entire, bodies appressed, spines abruptly spreading to deflexed, slender, 2–4 mm; apices of inner phyllaries narrow, flexuous, flattened, entire or finely erose. |
Heads | 1–many, borne singly or crowded in spiciform, racemiform, subcapitate, or sometimes more openly branched corymbiform arrays. |
1–10+, borne at tips of main stem and branches. |
Cypselae | dark brown, 5–6.5 mm, apical collars not differentiated; pappi 18–22 mm. |
brown, 5–6 mm, apical collars yellow, ca. 1 mm; pappi 25–30 mm. |
2n | = 34. |
= 18 (as C. terrae-nigrae), 20 + 1B. |
Cirsium hookerianum |
Cirsium engelmannii |
|
Phenology | Flowering summer (Jun–Sep). | Flowering spring–summer (May–Jul). |
Habitat | Moist soil, grasslands, aspen parkland, forest edges and openings, subalpine, alpine meadows | Tallgrass prairies, old fields, roadsides, oak savannas, forest edges, in calcareous clay or rarely sandy soils |
Elevation | 600–2900 m (2000–9500 ft) | 50–200 m (200–700 ft) |
Distribution |
ID; MT; WA; WY; AB; BC
|
LA; OK; TX |
Discussion | Cirsium hookerianum occurs from the Canadian Coast Ranges of British Columbia east to the northern Cascade Range and the northern Rocky Mountains. The relationship between C. hookerianum, C. kelseyi, which I have tentatively included in C. hookerianum, and C. longistylum needs further investigation. A case could be made for including all three in an expanded concept of C. hookerianum, but more investigation of the variation patterns is needed before this is done. Certainly C. kelseyi is better treated within or as a close ally of C. hookerianum than in C. scariosum (var. scariosum), where R. J. Moore and C. Frankton (1974) synonymized it. Cirsium hookerianum is known to hybridize with C. undulatum. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Cirsium engelmannii occurs mostly in the blackland prairies of eastern Texas. It ranges northward into southeastern Oklahoma and eastward to northwestern Arkansas. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 19, p. 148. | FNA vol. 19, p. 117. |
Parent taxa | Asteraceae > tribe Cardueae > Cirsium | Asteraceae > tribe Cardueae > Cirsium |
Sibling taxa | ||
Synonyms | C. kelseyi | C. virginianum var. filipendulum, C. terrae-nigrae |
Name authority | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 418. (1841) | Rydberg: Fl. Rocky Mts., 1069. (1917) |
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