Musk Thistle - Carduus nutans
Nodding Plumeless-thistle, Nodding Thistle, Nodding Thistle
Stems 30–150 cm. Herbage glabrate to villous. Leaves: basal wing-petiolate; blades oblanceolate, pinnately lobed, 6–20 cm long; cauline sessile, reduced upward. Inflorescence of solitary, sometimes nodding heads on spiny peduncles 2–30 cm long. Involucres 2–4 cm high; phyllaries lanceolate, outer reflexed; inner unarmed. Disk corollas 15–25 mm long. Achenes 4–5 mm long (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)
Size and shape of the imbricate, spine-tipped involucral bracts is used to distinguish members of the group from closely related species and from each other.
Members of the genus Carduus are distinguished by their simple pappus hairs from members of the genus Cirsium, which have feathery, plumose pappus hairs. Within the genus Carduus, members of the nutans group are distinguished by their large nodding heads from closely related, small- flowered plumeless and Italian thistles (C. acanthoides, C. crispus, C. pycnocephalus, and C. tenuiflorus) (McCarty 1984, Mulligan and Frankton 1954, Trumble and Kok 1982).
Carduus thoermeri is distinguished from other members of the nutans group by the broad (4-8 mm) fairly short blade of the involucral bract, which converges to a short awn tip. Carduus macrocephalus is distinguished from other North American members of the nutans group by the raised mid-vein of the long, broad, uniformly tapering involucral bract. Carduus nutans conforms to the illustration in the 3rd edition of Britton and Brown's illustrated flora (Gleason 1957). The involucral appendage is much narrower than in other members of the group. The involucral blade is narrow (1.5-3 mm), more or less hairy, and tapers gradually to an awn. Carduus sp. from British Columbia is characterized by a broad, fairly short involucral bract, converging slowly but not uniformly to the tip (McCarty 1985, Tutin et al. 1976).
In addition to these morphologically distinct species, hybrids of intermediate appearance have been reported between Carduus sp X C. thoermeri, C. thoermeri X C. macrocephalus and Carduus nutans (sensu lato) X C. acanthoides (McCarty 1985, Moore and Mulligan 1956, 1964, Mulligan and Moore 1961).
Members of the genus Carduus are native to Europe and Asia. The first records of Carduus nutans (sensu latu) in North America are from Harrisburg, Pennsylvania, between 1853 and 1866 (Stuckey and Forsythe 1971), and from Chatham, New Brunswick in 1878 (Mulligan and Frankton 1954). The musk thistle complex has been found in at least 3068 counties in 40 of the mainland states, with 12% of those countries rating their infestation as "economic" (Dunn 1976). The present North American distribution extends from the east to west coast in the deciduous forest and prairie biomes, from Canada southward through the central states. In the east, in the Great Valley of the Appalachians, Ohio, Kentucky, and Tennessee, musk thistle is most commonly associated with soils derived from limestone (Stuckey and Forsythe 1971, Batra 1978). In the Great Plains and the West this relationship does not necessarily hold true (Batra 1978). The near-absence of members of the C. nutans group from the Great Basin and the Nebraska sandhills is probably attributable to its moisture requirements for germination. Within the Nebraska sandhills, musk thistle is found in pockets of finer-textured soil (Steuter pers. comm.).
Nursery studies of plants from throughout the United States suggest that Carduus thoermeri is the most widespread species of the group in both the United States and Canada. Carduus macrocephalus is the dominant species in Montana and the intermountain region and Carduus sp. (unnamed) is restricted to British Columbia (McCarty 1985).
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Fields, roadsides, disturbed grasslands, riparian meadows; valleys, montane (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)
- Additional ReferencesLegend: View Online Publication
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- Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.