Cirsium engelmannii |
Cirsium undulatum |
|
---|---|---|
blackland thistle, Engelmann's thistle |
gray thistle, wavy-leaf thistle, wavyleaf or gray or pasture thistle |
|
Habit | Biennials or monocarpic perennials, 40–200 cm; taproots and clusters of coarse fibrous roots that often have tuberlike thickenings. | Perennials, 20–230 cm; deeply seated runner roots that produce adventitious buds. |
Stems | single, erect, often branched above middle, thinly arachnoid-tomentose, ± glabrate; branches few, ascending. |
1–several, erect or ascending, densely gray-tomentose; branches 0–few, usually above middle, ascending. |
Leaves | 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. |
blades elliptic to oblong or ovate, 10–40 × 1–10 cm, margins strongly undulate, coarsely dentate or shallowly to deeply lobed, lobes ascending to spreading, ± triangular, well separated to closely spaced, spinulose and coarsely dentate or usually cleft into 2–3 lanceolate to triangular, often entire-margined, spine-tipped divisions, main spines (yellowish), 2–12+ mm, abaxial densely gray-tomentose, adaxial faces thinly tomentose; basal sometimes present at flowering, winged-petiolate; principal cauline becoming sessile and progressively reduced distally, widest at base, bases ± auriculate-clasping to short-decurrent; distal reduced, spinier. |
Peduncles | 2–20+ cm, essentially naked with much reduced bracts. |
0–25+ cm. |
Involucres | ovoid to broadly cylindric or campanulate, 2.5–3.5 × 2–3 cm, thinly arachnoid. |
ovoid to hemispheric or broadly campanulate, 2.5–4.5 × 1.5–4.5 cm, loosely arachnoid on phyllary margins or glabrate. |
Corollas | pink to purple (white), 32–38 mm, tubes 15–20 mm, throats 6–9 mm, lobes 8–11 mm; style tips 5–6 mm. |
lavender to pink, purple, or white, 24–50 mm, tubes 12–28 mm, throats 6–14 mm, lobes 6.5–13 mm; style tips 5–7.5 mm. |
Phyllaries | 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. |
in 8–12 series, imbricate, ovate to lanceolate (outer) to linear-lanceolate (inner), abaxial faces with prominent glutinous ridge; outer and middle appressed, spines spreading, 1.5–5 mm; apices of inner narrow, often flexuous, flat, ± entire, spineless or weakly spiny. |
Heads | 1–10+, borne at tips of main stem and branches. |
1–10+, terminal on branches, in leafy, ± corymbiform arrays. |
Cypselae | brown, 5–6 mm, apical collars yellow, ca. 1 mm; pappi 25–30 mm. |
light to dark brown, 6–7 mm, bodies and apical collars concolorous, narrow; pappi 20–38 mm (usually scabridulous). |
2n | = 18 (as C. terrae-nigrae), 20 + 1B. |
= 26. |
Cirsium engelmannii |
Cirsium undulatum |
|
Phenology | Flowering spring–summer (May–Jul). | Flowering spring–autumn (May–Oct). |
Habitat | Tallgrass prairies, old fields, roadsides, oak savannas, forest edges, in calcareous clay or rarely sandy soils | Mixedgrass prairie, shortgrass prairie, Palouse prairie, sagebrush deserts, pinyon-juniper woodlands, openings in montane coniferous forests, often in disturbed areas |
Elevation | 50–200 m (200–700 ft) | 100–2800 m (300–9200 ft) |
Distribution |
LA; OK; TX |
AZ; CA; CO; GA; IA; ID; IL; IN; KS; MI; MN; MO; MT; ND; NE; NM; OK; OR; PA; SD; TX; UT; WA; WI; WY; AB; BC; MB; SK; Mexico (Chihuahua, Coahuila, Durango, Sonora)
|
Discussion | 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.) |
Cirsium undulatum is widely distributed in the wstern half of North America from the dry plains and plateaus of the Pacific Northwest eastward across the Great Plains to Manitoba and the Dakotas and south to Texas, New Mexico, and northwestern Mexico. It occurs in scattered localities in the Rocky Mountains and northeastern Great Basin region. At least some of the few widely scattered records from the eastern United States are probably introductions. Cirsium undulatum is both widespread and variable. Plants of the Great Plains region tend to be low-growing with a few large heads and elongate corollas. Plants of the Pacific Northwest are usually taller and produce smaller, more numerous heads with shorter corollas. A detailed study of this species might reveal races worthy of recognition as infraspecific taxa. Wavyleaf thistle is listed by California as a noxious weed. However, most reports of Cirsium undulatum in California are based upon misidentifications of C. canescens. Cirsium undulatum is known to hybridize with C. flodmanii, C. hookerianum, and C. scariosum var. coloradense. J. T. Howell (1960b) reported that C. undulatum was suspected to hybridize with C. brevifolium in the Pacific Northwest. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 19, p. 117. | FNA vol. 19, p. 120. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | C. virginianum var. filipendulum, C. terrae-nigrae | Carduus undulatus, C. megacephalum, C. undulatum var. megacephalum |
Name authority | Rydberg: Fl. Rocky Mts., 1069. (1917) | (Nuttall) Sprengel: Syst. Veg. 3: 374. (1826) |
Web links |
|