The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

Wyoming thistle

Habit Perennials polycarpic, 15–60(–90) cm; deep-seated woody tap-roots and caudices. 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

1–few, erect or ascending, arachnoid-tomentose or ± glabrate;

branches 0–5+, usually in distal 1/2, ascending.

Leaves

blades linear to oblong, oblanceolate, or elliptic, 5–25 × 0.6–7 cm, unlobed and merely spinulose or spiny-dentate to regularly pinnatifid, lobes 5–8(–many) pairs, well separated, usually with broad, U-shaped sinuses to crowded, linear to triangular-ovate, ascending-spreading to retrorse, merely spinulose to coarsely dentate or few lobed, main spines 2–7 mm, ± slender, abaxial faces gray to white, usually densely arachnoid-tomentose, sometimes ± glabrate, sometimes villous with septate trichomes along veins, adaxial green, glabrous or less commonly thinly to densely gray-tomentose;

basal often present at flowering, spiny winged-petiolate;

principal cauline well distributed, gradually reduced distally, proximal usually winged-petiolate, mid and distal sessile, bases decurrent as spiny wings 1.5–3.5 cm;

distalmost reduced, ± bractlike.

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.

Involucres

ovoid to campanulate, 1.8–2.7 × 1–2 cm, thinly arachnoid-tomentose 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 (creamy white), 18–25 mm, tubes 7–9 mm, throats 5.5–7.5 mm, lobes 4–8 mm;

style tips 3–5.5 mm.

Phyllaries

in 6–7 series, ± imbricate, green or with dark subapical patch or appendage, linear to linear-lanceolate, margins entire, abaxial faces with narrow glutinous ridge;

outer and middle bases appressed, apical appendages spreading to stiffly ascending, linear-lanceolate to acicular, entire, spines spreading or ascending, stout, 2–7 mm, often flattened;

apices of inner stiffly erect or sometimes flexuous, narrow, flat.

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 or in 2–3-headed clusters in ± congested flat-topped or racemiform arrays at tips of main stem and branches, sometimes also in distal axils.

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

tan to dark brown, 5–6 mm, apical collars yellow, narrow;

pappi 14–16 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

= 34.

Cirsium pulcherrimum

Asteraceae tribe Cardueae

Distribution
from FNA
CO; ID; MT; NE; UT; WY
[WildflowerSearch map]
[BONAP county map]
Mostly Old World; especially Mediterranean [Some species widely introduced]
Discussion

Varieties 2 (2 in the flora).

Cirsium pulcherrimum is closely related to C. clavatum. In southeastern Wyoming and northern Colorado some plants combine foliage and involucral characters of C. pulcherrimum var. pulcherrimum and C. clavatum var. americanum. The inheritance of these characters needs to be examined at the population level to determine whether the intermediates are hybrids or the products of past introgression or incomplete differentiation.

(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. Distal leaf face gray- to white-tomentose; cypselae without stramineous apical collar
var. aridum
1. Distal leaf face usually green, glabrous or ± glabrate, but sometimes persistently tomentose; cypselae often with narrow stramineous apical collar
var. pulcherrimum
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. 125. 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. 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. pulcherrimum var. aridum, C. pulcherrimum var. pulcherrimum
Acroptilon, Amberboa, Arctium, Carduus, Carlina, Carthamus, Centaurea, Cirsium, Crupina, Cynara, Echinops, Mantisalca, Onopordum, Plectocephalus, Saussurea, Silybum, Volutaria
Synonyms Carduus pulcherrimus family Asteraceae tribe Cynareae
Name authority (Rydberg) K. Schumann: Just’s Bot. Jahresber. 29(1): 566. (1903) Cassini
Web links