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Wyoming thistle

Nuttall's thistle

Habit Perennials polycarpic, 15–60(–90) cm; deep-seated woody tap-roots and caudices. Biennials, 20–350 cm; taprooted.
Stems

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

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

usually single, erect, glabrous or villous with septate trichomes;

branches few–many, 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.

blades narrowly to broadly elliptic, (10–)15–60 × (2–)5–15 cm, thin, ± flexible, deeply pinnatifid, lobes narrow, spreading, coarsely dentate or lobed, main spines 2–5 mm, abaxial faces thinly tomentose but often wholly glabrate in age, adaxial glabrous or sparsely villous with septate trichomes;

basal often absent at flowering, petioles slender, winged, bases tapered;

principal cauline becoming sessile and gradually reduced distally, bases spiny-lobed, sometimes decurrent;

distal reduced to linear bracts.

Peduncles

0–15 cm.

1–15 cm, essentially naked (not overtopped by crowded distal leaves).

Involucres

ovoid to campanulate, 1.8–2.7 × 1–2 cm, thinly arachnoid-tomentose or glabrate.

hemispheric to campanulate, 1.5–2.5 × 1–2.5 cm, thinly arachnoid or glabrate.

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.

white to pink, lavender, or purple, 17–25 mm, tubes 5–11 mm, throats 4–7 mm (noticeably wider than tubes), lobes 5–7 mm;

style tips 3–4.5 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.

in 6–10 series, strongly imbricate, green or brownish, ovate or elliptic (outer) to linear-lanceolate (inner), abaxial faces with narrow glutinous ridge;

outer and middle appressed, bodies entire, spines abruptly spreading, slender, 1–2(–3) mm;

apices of inner often flexuous, flat, attenuate.

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.

few–many, in open corymbiform or paniculiform arrays.

Cypselae

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

pappi 14–16 mm.

dark brown, 3–4 mm, apical collars stramineous, 0.5 mm;

pappi 17–21 mm (longer bristles shorter than corollas).

2n

= 34.

= 24, 26, 28.

Cirsium pulcherrimum

Cirsium nuttallii

Phenology Flowering summer (Jun–Aug).
Habitat Roadsides, ditches, woodlands, usually in damp soil
Elevation 0–100 m (0–300 ft)
Distribution
from FNA
CO; ID; MT; NE; UT; WY
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; FL; GA; LA; MS; NC; SC; TX; VA
[WildflowerSearch map]
[BONAP county map]
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.)

Cirsium nuttallii occurs on the southern coastal plain from southeastern Virginia to southern Florida and west to eastern Louisiana.

(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
Source FNA vol. 19, p. 125. FNA vol. 19, p. 119.
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. 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
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. 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. pulcherrimum var. aridum, C. pulcherrimum var. pulcherrimum
Synonyms Carduus pulcherrimus Carduus glaber, Carduus nuttallii
Name authority (Rydberg) K. Schumann: Just’s Bot. Jahresber. 29(1): 566. (1903) de Candolle: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 6: 651. (1838)
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