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pasture thistle

Habit Biennials or monocarpic perennials, 25–100 cm; sometimes perennating by root sprouts. Annuals or perennials (sometimes coarse and/or robust, often prickly-spiny and thistlelike [subshrubs, shrubs, or trees]; rarely dioecious, e.g., some Cirsium spp.).
Stems

erect, villous with septate trichomes and sometimes thinly arachnoid tomentose;

branches 0–few, distal, ascending.

Leaves

blades oblong-elliptic, 5–30+ × 2–10 cm, ± undulate, shallowly to deeply pinnatifid, lobes ovate to broadly triangular, usually separated by broad sinuses, spinose-dentate or lobed, main spines 1.5–7 mm, slender to stout, abaxial faces villous with septate trichomes, at least along veins, sometimes thinly arachnoid, adaxial faces villous with septate trichomes and thinly arachnoid tomentose or subglabrous;

basal often present at flowering, bases tapered;

principal cauline sessile, moderately reduced distally, bases often auriculate-clasping;

distal reduced, similar to proximal.

basal and/or cauline; alternate; ± petiolate or sessile; (leaf bases often decurrent on stems) margins usually lobed to dissected, sometimes dentate or entire (usually spiny).

Peduncles

0–15+ cm (above distal leaves), leafy-bracted.

Involucres

broadly cylindric to ovoid, 3.5–5 cm, 2.5–3 cm diam. (appearing much wider and hemispheric to campanulate in pressed specimens), loosely arachnoid on phyllary margins or glabrate.

Receptacles

flat to convex, usually epaleate (often pitted and often bristly-setose or densely hairy).

Ray florets

0 (corollas of peripheral florets in radiant heads often notably enlarged, usually 5-lobed, sometimes zygomorphic and raylike or ± 2-lipped).

Peripheral (pistillate) florets

0 or (in disciform heads) in 1–3+ series;

corollas (usually present) usually yellow, sometimes ochroleucous or cyanic.

Disc florets

bisexual and fertile (rarely functionally staminate);

corollas yellow, cyanic, or white, usually actinomorphic, lobes 5, usually narrowly triangular to ± linear, seldom deltate (sometimes unequal, corollas then ± zygomorphic);

anther bases ± tailed, apical appendages usually oblong (filaments sometimes papillate to pilose; connate in Silybum);

styles (bisexual, fertile florets) distally enlarged or swollen, usually dilated and/or with rings of hairs at or near point of bifurcation, abaxially smooth or papillate to hairy (at least distally, sometimes ± throughout), “branches” often connate, adaxially continuously stigmatic ± to tips, apices rounded to acute, appendages essentially none.

Corollas

pink to purple (white), 40–60 mm, tubes 20–35 mm, throats 11–15 mm, lobes 7–10 mm;

style tips 3–7 mm.

Phyllaries

in 8–10 series, imbricate, ovate or lanceolate (outer) to lance-linear (inner), abaxial faces with ± prominent glutinous ridge, outer and middle appressed, apices ascending to spreading, spines 1.5–6 mm;

apices of middle and inner narrowed and scabrid-denticulate, innermost spineless, tapered and entire or with expanded, erose-denticulate, flexuous tips.

usually persistent [readily falling], in (1–)3–5+ series, usually distinct, usually unequal, usually herbaceous (sometimes fleshy), margins (entire or denticulate to pectinate, sometimes spiny) and apices seldom notably scarious (apices often spinose or ± expanded into distinct, often fimbriate-fringed, pectinate, and/or spiny appendages).

Calyculi

0 (involucres sometimes closely subtended by leaflike peduncle bracts).

Heads

1–few, borne singly at tips of main stem and branches, often closely subtended by 1–several bracts.

mostly homogamous (usually discoid, sometimes disciform or radiant, then peripheral florets usually pistillate or neuter, sometimes bisexual or with staminodes), borne singly or in corymbiform, paniculiform, or racemiform arrays (heads with 1 floret each aggregated into second-order heads in Echinops).

Cypselae

stramineous to brown, 3.5–5 mm, apical collars yellow or colored like body;

pappi 35–45 mm.

usually monomorphic within heads (often thick-walled, hard, nutlike, receptacular attachments basal or lateral, bases sometimes each with an elaiosome), usually ellipsoid, obovoid, or ovoid, sometimes rounded-prismatic, terete, 4–5-angled, or ± compressed, rarely beaked, bodies usually smooth, sometimes rugose or 10- or 20-nerved (glabrous or puberulent to villous; often with apical umbo and/or crown in addition to pappus);

pappi (rarely 0) readily falling or persistent, usually of fine to coarse, barbellate to plumose bristles, sometimes of scales, sometimes both bristles and scales.

2n

= 30.

Cirsium pumilum

Asteraceae tribe Cardueae

Distribution
from FNA
CT; DE; IA; IL; IN; MA; MD; ME; MI; MN; NC; NH; NJ; NY; OH; PA; RI; SC; VA; VT; WI; WV; ON; United States
[WildflowerSearch map]
[BONAP county map]
Mostly Old World; especially Mediterranean [Some species widely introduced]
Discussion

Varieties 2 (2 in the flora).

Flowers of Cirsium pumilum are reportedly sweetly scented.

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

Genera 83, species 2500 (17 genera, 116 species in the flora).

The circumscription for Cynareae adopted here is the traditional one and includes the three elements (Cynareae in the narrow sense, Carlineae, and Echinopeae) recognized as tribally distinct by M. Dittrich (1977[1978]). Work by K. Bremer (1987) supported the Dittrich scheme. A traditional circumscription of Cynareae was maintained by J. L. Panero and V. A. Funk (2002).

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

Key
1. Spines of outer phyllaries stout, 3–6 mm; plants usually with several long branches; leaves usually lobed nearly to the midvein; roots rarely and only slightly tuberous-thickened; cypselae usually 3.5– 4 mm
var. pumilum
1. Spines of outer phyllaries slender, 1.5–3 mm; plants simple or distally with a few short branches; leaves usually shallowly lobed; roots often tuberous-thickened; cypselae usually 4.5–5 mm
var. hillii
1. Leaf margins spiny
→ 2
1. Leaf margins not spiny (tips sometimes ± spinose-apiculate)
→ 10
2. Florets 1 per head (heads in globose, second-order heads)
Echinops
2. Florets 3–250+ per head (heads borne singly or in ± open arrays, not in globose second-order heads)
→ 3
3. Stems winged
→ 4
3. Stems not or rarely winged (some Cirsium spp.)
→ 5
4. Receptacles bearing setiform scales ("flattened bristles"), (not pitted); cypselar attachments slightly lateral; pappus bristles usually distinct, sometimes basally connate
Carduus
4. Receptacles not bristly (deeply pitted); cypselar attachments basal; pappus bristles basally connate
Onopordum
5. Leaves variegated (stamen filaments connate)
Silybum
5. Leaves not variegated (stamen filaments distinct)
→ 6
6. Corollas yellow to orange, red, or ± purple; cypsela attachments lateral; pappi 0 or of distinct, minutely barbed (not plumose) setiform scales ("flattened bristles") or subulate scales
→ 7
6. Corollas white or purplish to red; cypsela attachments basal or oblique-basal; pappi of basally connate, plumose setiform scales ("flattened bristles")
→ 8
7. Heads discoid (all florets fertile); receptacles bearing subulate scales; cypselae 4-angled
Carthamus
7. Heads disciform (peripheral florets sterile); receptacles bristly ("flat- tened bristles"), cypselae terete, 20-ribbed
Centaurea
8. Receptacles scaly (sometimes bristly); cypsela attachments oblique- basal
Carlina
8. Receptacles densely bristly-setose; cypselar attachments basal
→ 9
9. Involucres 35–100+ mm diam. (largest leaves 60–150 cm; recep- tacles becoming fleshy)
Cynara
9. Involucres 10–50 mm diam. (largest leaves 20–50(–110) cm; receptacles usually not notably fleshy)
Cirsium
10. Heads discoid (all florets bisexual and fertile)
→ 11
10. Heads radiant or disciform (peripheral florets usually neuter)
→ 15
11. Cypselar attachments ± lateral
→ 12
11. Cypselar attachments basal
→ 13
12. Phyllary appendages entire or lacerate, not fringed; pappi of ± caducous, dis- tally plumose bristles
Acroptilon
12. Phyllary appendages dentate or fringed; pappi 0 or if persistent, then non- plumose bristles or scales
Centaurea
13. Phyllary apices spiny, hooked; bristles of pappus distinct, not plumose
Arctium
13. Phyllary apices spiny or not, not hooked; setiform scales ("flattened bristles") of pappus basally connate, plumose
→ 14
14. Receptacles densely long-bristly ("flattened bristles") (becoming fleshy); florets 100–250+
Cynara
14. Receptacles usually subulate-scaly, sometimes bristly or naked (not fleshy); florets 10–20
Saussurea
15. Heads disciform
→ 16
15. Heads radiant
→ 17
16. Phyllary appendages dentate or fringed, spiny or not; receptacles bristly ("flat- tened bristles")
Centaurea
16. Phyllary appendages 0 (apices acute, entire); receptacles bearing subulate scales
Crupina
17. Phyllary appendages 0
→ 18
17. Phyllary appendages present
→ 19
18. Biennials or perennials; spines on phyllary apices caducous; cypsela apices not coronate
Mantisalca
18. Annuals; spines on phyllary apices persistent; cypsela apices coronate.
Volutaria
19. Cypselae compressed (oblong; attachment scars rimmed, rims whitish, swollen), apices denticulate
Amberboa
19. Cypselae ± terete (barrel-shaped; attachment scars not rimmed), apices entire
→ 20
20. Annuals; leaf margins mostly entire or denticulate to serrulate; cypsela attachment oblique-basal; involucres 20–40 mm diam.; phyllary bodies linear, margins entire, appendages fimbriate; corollas of peripheral florets 30–70 mm
Plectocephalus
20. Annuals, biennials, or perennials; leaf margins entire or toothed to pinnately lobed; involucres 10–25(–40) mm diam.; cypsela attachment lateral; phyllary bodies oblong to ovate or obovate, margins fimbriate, appendages fimbriate; corollas of peripheral florets 15–30(–45) mm
Centaurea
Source FNA vol. 19, p. 116. FNA vol. 19, p. 82.
Parent taxa Asteraceae > tribe Cardueae > Cirsium Asteraceae
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. 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. 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. pumilum var. hillii, C. pumilum var. pumilum
Acroptilon, Amberboa, Arctium, Carduus, Carlina, Carthamus, Centaurea, Cirsium, Crupina, Cynara, Echinops, Mantisalca, Onopordum, Plectocephalus, Saussurea, Silybum, Volutaria
Synonyms Carduus pumilus family Asteraceae tribe Cynareae
Name authority (Nuttall) Sprengel: Syst. Veg. 3: 375. (1826) Cassini
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