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bristly or horrid or yellow or bull thistle, bristly thistle, bull thistle, horrid thistle, yellow thistle

graygreen thistle, peregrine thistle

Habit Biennials or perennials, (± fleshy), 15–250 cm; stout taproots and a fascicle of fleshy lateral roots, often perennating by root sprouts. Biennials or perennials, 25–120 cm, pubescence a mixture of fine, non-septate arachnoid trichomes and coarser, septate trichomes, especially along stems and on midveins on abaxial leaf faces, usually ± loose and irregularly deciduous from leaves in age; taprooted.
Stems

1–several, usually erect, often stout, glabrous to densely tomentose;

branches 0–many, spreading to ascending, short, stout.

usually 1, erect, ± gray-tomentose, sometimes villous with septate trichomes;

branches 0–10+, usually arising in distal 1/2, ascending, usually reaching a ± common height.

Leaves

blades linear to oblanceolate or oblong-elliptic, 10–40 × 2–10 cm, unlobed and spiny-dentate to deeply pinnatifid, lobes spiny-dentate or coarsely lobed, main spines stout, 5–30 mm, abaxial faces subglabrous to loosely tomentose, adaxial glabrous to ± densely villous with septate trichomes;

basal present at flowering, spiny winged-petiolate, bases often tapered;

principal cauline sessile, well distributed, often not much reduced distally, bases often ± auriculate-clasping;

distal cauline often spinier than the proximal.

blades linear-oblong to oblanceolate or elliptic, 10–30 × 3–7 cm, shallowly to deeply pinnatifid with 3–8 pairs of lobes, longer than 2 cm, lobes well separated, linear to triangular-ovate, dentate to lobed proximally, main spines slender, 2–7 mm, faces green to gray, thinly to densely arachnoid-tomentose with fine, non-septate trichomes, sometimes villous with septate trichomes along veins, usually ± loose and irregularly deciduous from leaves in age;

basal often present at flowering, sessile or winged-petiolate;

principal cauline mostly in proximal 1/2, winged-petiolate or sessile, bases narrowed, auriculate, veins often prominently raised on abaxial faces;

distal sessile, auriculate-clasping or short-decurrent 1–10 mm, progressively reduced becoming bractlike, often unlobed or less deeply divided and sometimes spinier than proximal.

Peduncles

0–5 cm.

(0–)2–15 cm.

Involucres

hemispheric to campanulate, 3–5 × 3–8 cm.

ovoid to hemispheric or campanulate, 2–3 × 1.5–3.5 cm, ± arachnoid-floccose, often glabrate.

Corollas

white to yellow, pink, purple, or red, 30–47 mm, tubes 11–30 mm, throats 6–10 mm, lobes 7–10 mm;

style tips 3–5 mm.

creamy white to purplish, 20–31 mm, tubes 8–14 mm, throats 5.5–10 mm, lobes 6–7 mm;

style tips 4–6 mm.

Phyllaries

in 5–9 series, subequal to imbricate, light green to stramineous, lanceolate to linear, distally often with reddish margins, abaxial faces without glutinous ridge, often ± thinly tomentose, often scabridulous in submarginal bands;

outer and middle appressed-ascending, bodies usually reddish-tinged, margins setulose-ciliolate, apices acuminate, spines 1–2 mm, weak;

apices of inner straight, flat.

in 8–10 series, subequal to strongly imbricate, green, linear to lanceolate (outer) to linear (inner), entire, abaxial faces with inconspicuous to prominent glutinous ridge;

outer and mid bodies loosely spreading to ascending or appressed, apices subappressed to ascending or spreading, flat, spines ascending to spreading, fine, 2–4 mm;

apices of inner commonly flexuous or reflexed, narrow, flat, scarious.

Heads

1–20 in subcapitate to corymbiform arrays (each closely subtended by an involucre-like ring of spiny-margined bracts).

borne singly, terminal on main stem and branches, sometimes also in distal axils, erect, not subtended by well-developed leaves, collectively forming corymbiform or racemiform arrays.

Cypselae

straw-colored to tan, 4–6 mm, apical collars weakly differentiated;

pappi 25–35 mm.

tan to dark brown, 5–7.5 mm, apical collars not differentiated;

pappi 16–25 mm.

2n

= 32, 33, 34, 35.

Cirsium horridulum

Cirsium cymosum

Distribution
from FNA
AL; AR; CT; DE; FL; GA; LA; MA; MD; ME; MS; NC; NH; NJ; NY; OK; PA; RI; SC; TN; TX; VA; Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; ID; MT; NV; OR; WY
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 4 (3 in the flora).

Although several variants have been given taxonomic recognition as species, these seem at most races. Flower color varies greatly, sometimes within populations and sometimes on a populational or regional basis. Herbarium specimens are sometimes difficult to assign to variety.

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

Varieties 2 (2 in the flora).

Past floras have treated Cirsium cymosum and C. canovirens as separate species. In my examination of these plants across their combined ranges I realized that they are connected by numerous intermediates and that I could find no characters that consistently distinguish them.

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

Key
1. Stems densely tomentose; involucres ± densely tomentose
var. horridulum
1. Stems glabrous or sparsely tomentose; involucres glabrous
→ 2
2. Leaves shallowly to deeply pinnatifid, main spines 10–30 mm
var. megacanthum
2. Leaves spinose-dentate to shallowly pinnatifid, main spines mostly 5–10 mm
var. vittatum
1. Larger heads 20–35 mm diam.; outer phyllaries elongate, often nearly as long as inner; glutinous ridge narrow, weakly developed
var. cymosum
1. Larger heads 15–25 mm diam.; outer phyllaries usually much shorter than inner phyllaries; glutinous ridge prominent, well developed, appearing dark brown on dry specimens
var. canovirens
Source FNA vol. 19, p. 114. FNA vol. 19, p. 136.
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. engelmannii, C. flodmanii, C. foliosum, C. fontinale, C. grahamii, C. helenioides, C. hookerianum, 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. 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. 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
Subordinate taxa
C. horridulum var. horridulum, C. horridulum var. megacanthum, C. horridulum var. vittatum
C. cymosum var. canovirens, C. cymosum var. cymosum
Synonyms Carduus cymosus, C. botrys, C. triacanthum
Name authority Michaux: Fl. Bor.-Amer. 2: 90. (1803) (Greene) J. T. Howell: Amer. Midl. Naturalist 30: 37. (1943)
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