Carduus nutans |
Asteraceae tribe Cardueae |
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chardon penché, common harebell, musk thistle, nodding plumeless-thistle, nodding thistle |
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Habit | Annuals or biennials, 40–200+ cm. | 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 | glabrous to tomentose; teeth of wings to 10 mm, wing spines 2–10 mm. |
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Leaves | basal tapering to winged petioles, blades 10–40 cm, margins 1–2x-pinnately lobed; cauline sessile, shorter, margins less divided, glabrous or ± hairy. |
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). |
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Peduncles | 2–30 cm, unwinged distally or throughout, finely tomentose. |
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Involucres | hemispheric, 20–60 mm × 20–70 mm. |
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Receptacles | flat to convex, usually epaleate (often pitted and often bristly-setose or densely hairy). |
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Ray florets | 0 (corollas of peripheral florets in radiant heads often notably enlarged, usually 5-lobed, sometimes zygomorphic and raylike or ± 2-lipped). |
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Peripheral (pistillate) florets | 0 or (in disciform heads) in 1–3+ series; corollas (usually present) usually yellow, sometimes ochroleucous or cyanic. |
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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. |
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Corollas | purple, 15–28 mm, lobes 2.5–3 times longer than throat. |
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Phyllaries | lanceolate to ovate, outer and middle with appressed bases 2–4 mm wide and spreading to reflexed, appendages 2–7 mm wide, proximally glabrous or ± tomentose, distally glabrous to minutely scabridulous, spine tips 1–4 mm, inner phyllaries with unarmed, straight or twisted 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). |
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Calyculi | 0 (involucres sometimes closely subtended by leaflike peduncle bracts). |
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Heads | borne singly or in corymbiform arrays, sometimes a few axillary, at least terminal head usually conspicuously pedunculate, often nodding, 20–40 mm. |
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). |
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Cypselae | golden to brown, 4–5 mm; pappus bristles 13–25 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. |
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2n | = 16. |
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Carduus nutans |
Asteraceae tribe Cardueae |
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Phenology | Flowering late spring–summer (May–Sep). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Habitat | Aggressive weed of waste ground, pastures, roadsides, fields | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Elevation | 0–3000 m (0–9800 ft) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Distribution |
AL; AR; AZ; CA; CO; DC; GA; IA; ID; IL; IN; KS; KY; LA; MD; MO; MS; MT; NC; ND; NE; NJ; NM; NV; NY; OH; OK; OR; PA; SC; SD; TN; TX; UT; VA; WA; WI; WV; WY; AB; BC; MB; NB; NF; NS; ON; QC; SK; Eurasia [Introduced in North America]
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Mostly Old World; especially Mediterranean [Some species widely introduced] |
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Discussion | Although reported from Connecticut, Delaware, Indiana, Massachusetts, Michigan, New Hampshire, Ohio, and Rhode Island, I have seen no specimens of Carduus nutans from those places. Carduus nutans is part of a variable complex that has been treated as one to several species or as a single species with several subspecies or varieties. The New World plants apparently represent multiple introductions, probably representing more than one of these taxa. Various intermediates are evident, and many specimens cannot be reliably assigned. Insufficient evidence exists to reliably apply the names of the various segregate entities to North American material. In a biosystematic study, two subspecies of C. nutans were differentiated in Canada (A. M. Desrochers et al. 1988). Subspecies nutans was characterized as having arachnoid phyllaries with the terminal appendage only slightly wider than the appressed phyllary base, moderately to densely pubescent leaf bases, and a head diameter of 1.5–3.5 cm. Subspecies leiphyllus in contrast has glabrous phyllaries with the terminal appendage definitely wider than the base, glabrous or slightly pubescent bases, and heads 1.8–7 cm in diameter. Subspecies nutans was distributed in eastern Canada from Newfoundland to southern Ontario and subsp. leiocephalus from Ontario to British Columbia. Whether the results of the study (Desrochers et al.) are applicable to all the populations of musk thistles occurring in the United States has not been determined. Hybrids between Carduus acanthoides and C. nutans (C. ×orthocephalus Wallroth) have been documented from Ontario and Wisconsin and probably occur at other sites where the parental taxa co-occur. Nodding thistle is one of the most serious weeds in North America. It is unpalatable to wildlife and livestock and often forms dense, impenetrable stands in pastures and rangelands. It readily colonizes disturbed sites in many different habitats. A single large terminal head can produce as many as 1200 cypselae. Efforts to control musk thistle infestations with Rhinocyllus conicus, a European seed head weevil, have met with some success, but concerns have been raised because this parasite also attacks native Cirsium species. (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.) |
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Key |
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Source | FNA vol. 19, p. 93. | FNA vol. 19, p. 82. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Parent taxa | Asteraceae > tribe Cardueae > Carduus | Asteraceae | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Sibling taxa | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Synonyms | C. macrocephalus, C. macrolepis, C. nutans subsp. leiophyllus, C. nutans subsp. macrocephalus, C. nutans var. macrocephalus, C. nutans subsp. macrolepis, C. nutans var. vestitus, C. thoermeri | family Asteraceae tribe Cynareae | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | Linnaeus: Sp. Pl. 2: 821. (1753) | Cassini | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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