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blackland thistle, Engelmann's thistle

Beaumont thistle, yellowspine thistle

Habit Biennials or monocarpic perennials, 40–200 cm; taproots and clusters of coarse fibrous roots that often have tuberlike thickenings. Perennials, 30–90 cm; crown sprouts or runner roots producing adventitious buds.
Stems

single, erect, often branched above middle, thinly arachnoid-tomentose, ± glabrate;

branches few, ascending.

1–20+, erect or ascending, densely gray-tomentose with non-septate trichomes;

branches 0 or few, usually in distal 1/2, 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 oblong to narrowly elliptic, 10–30 × 2–8 cm, strongly undulate, margins coarsely dentate or shallowly to deeply pinnatifid with 8–15 pairs of lobes 0.5–2 cm, often revolute, lobes ± triangular, closely spaced, spreading, spinose-dentate and cleft into 2–5 spine-tipped divisions, main spines 5–20 mm, yellowish, abaxial faces densely white-tomentose, adaxial thinly gray-tomentose;

basal usually present at flowering, winged-petiolate;

principal cauline sessile, progressively reduced distally, bases ± auriculate to long-decurrent as spiny wings;

distal cauline usually much reduced, less lobed.

Peduncles

2–20+ cm, essentially naked with much reduced bracts.

0–4 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 × 2.5–4.5 cm in first-formed heads, often smaller in later ones, 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.

white or pale lavender to purple, pink, or red, 25–45 mm, tubes 8–25 mm, throats 6–17 mm, lobes 6–15 mm;

style tips 2–8 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 5–10 series, imbricate, ovate (outer) to linear-lanceolate (inner), margins entire, abaxial faces with narrow glutinous ridge;

outer and middle appressed, spines spreading, 3–12 mm;

apices of inner often flexuous, expanded and flat, scabrid-margined, sometimes erose, spineless.

Heads

1–10+, borne at tips of main stem and branches.

1–few, in leafy, ± corymbiform arrays.

Cypselae

brown, 5–6 mm, apical collars yellow, ca. 1 mm;

pappi 25–30 mm.

light brown, sometimes with lighter or darker streaks, 6–9 mm, apical collars colored like the body, narrow;

pappi (white or tawny), 20–40 mm, usually noticeably shorter than corolla.

2n

= 18 (as C. terrae-nigrae), 20 + 1B.

= 30, 31, 32, 34.

Cirsium engelmannii

Cirsium ochrocentrum

Phenology Flowering spring–summer (May–Jul).
Habitat Tallgrass prairies, old fields, roadsides, oak savannas, forest edges, in calcareous clay or rarely sandy soils
Elevation 50–200 m (200–700 ft)
Distribution
from FNA
LA; OK; TX
[BONAP county map]
from FNA
AZ; CA; CO; KS; NE; NM; OK; SD; TX; UT; WY; n Mexico
[WildflowerSearch map]
[BONAP county map]
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.)

Varieties 2 (2 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Stems densely leafy, nodes crowded; leaves often long- decurrent; corollas white or pale lavender to purple
var. ochrocentrum
1. Stems leafy, nodes usually well separated; distal cauline leaves clasping, or if decurrent spiny wing usually less than 1 cm; corollas red, pink, or reddish purple (rarely white)
var. martinii
Source FNA vol. 19, p. 117. FNA vol. 19, p. 123.
Parent taxa Asteraceae > tribe Cardueae > Cirsium Asteraceae > tribe Cardueae > Cirsium
Sibling taxa
C. altissimum, C. andersonii, C. andrewsii, C. arizonicum, C. arvense, C. barnebyi, C. brevifolium, C. brevistylum, C. canescens, C. carolinianum, C. ciliolatum, C. clavatum, C. crassicaule, C. cymosum, C. discolor, C. douglasii, C. drummondii, C. eatonii, C. edule, C. flodmanii, C. foliosum, C. fontinale, C. grahamii, C. helenioides, C. hookerianum, C. horridulum, C. hydrophilum, C. inamoenum, C. joannae, C. kamtschaticum, C. lecontei, C. longistylum, C. mohavense, C. muticum, C. neomexicanum, C. nuttallii, C. occidentale, C. ochrocentrum, C. ownbeyi, C. palustre, C. parryi, C. perplexans, C. pitcheri, C. praeteriens, C. pulcherrimum, C. pumilum, C. quercetorum, C. remotifolium, C. repandum, C. rhothophilum, C. rydbergii, C. scariosum, C. texanum, C. tracyi, C. turneri, C. undulatum, C. vinaceum, C. virginianum, C. vulgare, C. wheeleri, C. wrightii
C. altissimum, C. andersonii, C. andrewsii, C. arizonicum, C. arvense, C. barnebyi, C. brevifolium, C. brevistylum, C. canescens, C. carolinianum, C. ciliolatum, C. clavatum, C. crassicaule, C. cymosum, C. discolor, C. douglasii, C. drummondii, C. eatonii, C. edule, C. engelmannii, C. flodmanii, C. foliosum, C. fontinale, C. grahamii, C. helenioides, C. hookerianum, C. horridulum, C. hydrophilum, C. inamoenum, C. joannae, C. kamtschaticum, C. lecontei, C. longistylum, C. mohavense, C. muticum, C. neomexicanum, C. nuttallii, C. occidentale, C. ownbeyi, C. palustre, C. parryi, C. perplexans, C. pitcheri, C. praeteriens, C. pulcherrimum, C. pumilum, C. quercetorum, C. remotifolium, C. repandum, C. rhothophilum, C. rydbergii, C. scariosum, C. texanum, C. tracyi, C. turneri, C. undulatum, C. vinaceum, C. virginianum, C. vulgare, C. wheeleri, C. wrightii
Subordinate taxa
C. ochrocentrum var. martinii, C. ochrocentrum var. ochrocentrum
Synonyms C. virginianum var. filipendulum, C. terrae-nigrae
Name authority Rydberg: Fl. Rocky Mts., 1069. (1917) A. Gray: Mem. Amer. Acad. Arts, n. s. 4: 110. (1849)
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