Flora of North America species comparison

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Carduus pycnocephalus

Carduus crispus

compact-head thistle, Italian plumeless thistle, Italian thistle

chardon crépu, curled thistle, curly plumeless-thistle, welted thistle
Habit Annuals or biennials, 30–150 cm.
Stems

openly branching, villous with curled, septate hairs to nearly glabrous, spiny wings to 1.5 cm wide, wing spines to 3 mm.
Leaves

basal tapering to winged petioles, blades 10–20 cm, margins spiny-toothed to ± shallowly pinnately lobed;

cauline sessile, gradually smaller, margins often more deeply divided, marginal spines to 3 mm;

abaxial leaf faces ± tomentose with long, one-celled hairs and/or long, curled, septate hairs along veins or glabrate;

adaxial faces sparsely hairy or glabrate.
Peduncles

spiny-winged to near apex or throughout, to 4 cm.
Involucres

± spheric, 12–17 × 12–17 mm.
Corollas

purple or ± white, 11–16 mm, lobes ca. 3.5 times length of throat.
Phyllaries

narrowly lanceolate, outer and middle with appressed bases ca. 1 mm wide and appressed to spreading appendages 0.5–1 mm wide, spine tips 1–1.5 mm, inner with unarmed, straight tips.
Heads

borne singly or in groups of 2–5, 15–18 mm.
Cypselae

light brown to gray-brown, 2.5–3.8 mm;

pappus bristles 11–13 mm.
2n

= 16 (Sweden).

Carduus pycnocephalus

Carduus crispus
Phenology Flowering summer–fall (Jul–Sep).
Habitat Weed of waste ground, pastures, roadsides, fields
Elevation 0–500 m [0–1600 ft]
Distribution
from FNA
AL; AR; CA; ID; MS; NY; OR; PA; SC; TX; Eurasia (Mediterranean region)
[WildflowerSearch map]
[BONAP county map]
from FNA
NJ; PA; BC; NB; NS; ON; QC; Eurasia [Introduced in North America]
[BONAP county map]
Discussion

Subspecies 2 (1 in the flora).

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

Canadian distributions above follow R. J. Moore and C. Frankton (1974); I have not seen those specimens. Carduus crispus has been reported also from Arkansas, Connecticut, Iowa, Illinois, Maine, Maryland, Massachusetts, Missouri, New York, North Dakota, Ohio, Rhode Island, Vermont, Virginia, and West Virginia; I have not seen specimens from those states.

Two subspecies of Carduus crispus have been recognized (S. M. A. Kazmi 1964); those are not differentiated here.

Carduus crispus closely resembles the much more common C. acanthoides. Some published records of C. crispus are probably C. acanthoides. Although the degree of spininess and tough versus brittle stems were used as key characters (A. Cronquist 1980; H. A. Gleason and A. Cronquist 1991) to differentiate the two taxa, both characters are subjective, and the second is impractical with dry material.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 19, p. 93. FNA vol. 19, p. 92.
Parent taxa Asteraceae > tribe Cardueae > Carduus Asteraceae > tribe Cardueae > Carduus
Sibling taxa
C. acanthoides, C. crispus, C. nutans, C. tenuiflorus
C. acanthoides, C. nutans, C. pycnocephalus, C. tenuiflorus
Subordinate taxa
C. pycnocephalus subsp. pycnocephalus
Name authority Linnaeus: Sp. Pl. ed. 2, 2: 1151. (1763) Linnaeus: Sp. Pl. 2: 821. (1753)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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