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Cirsium occidentale (Nutt.) Jeps.  
Go To Encyclopedia of Life...
Family: Asteraceae
Cobwebby Thistle
Cirsium occidentale image
Gerald and Buff Corsi  
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David J. Keil in Flora of North America (vol. 19, 20 and 21)
Biennials, 5-400 cm; taproots. Stems usually 1, thinly to densely gray- or white-tomentose, sometimes ± glabrate; branches few-many, usually from above mid or near base in compact, moundlike dwarf plants, ascending to spreading. Leaves: blades oblong-elliptic to oblanceolate, 6-40 × 1.5-10+ cm, shallowly to deeply pinnatifid, lobes usually rigidly spreading, undivided or with 1-2 pairs of coarse teeth or lobes, main spines 5-15 mm, both faces gray- to white-tomentose, sometimes ± glabrate or adaxial faces green, thinly arachnoid-tomentose; basal sometimes present at flowering, petiolate or sessile and bases tapered. spiny-winged; principal cauline much reduced distally, sessile, bases decurrent or not, as spiny wings; distal much reduced, linear, ± bractlike. Heads 1-many in loose to tight clusters (barely raised above rosette in dwarf plants). Peduncles 1-30 cm. Involucres ovoid to spheric, 1.5-5 × 1.5-8 cm, arachnoid to ± loosely tomentose, often adjacent phyllaries connected by conspicuous arachnoid trichomes, sometimes glabrous or glabrate. Phyllaries in 7-10 series, subequal to strongly imbricate, green or stramineous to purple-tinged, linear to narrowly lanceolate, abaxial faces without glutinous ridge; outer and mid bodies appressed, entire, apices deflexed to spreading or ascending, short-triangular to elongate, linear-acicular, spines spreading to reflexed, 1-10+ mm; apices of inner erect, often flexuous, flat. Corollas white to lavender, pink, rose-purple, or red, 18-40 mm, tubes 8-18 mm, throats 5-7 mm, lobes 5-10 mm; style tips 4-5 mm. Cypselae ± brown, 5-6 mm, apical collars not differentiated; pappi 15-30 mm.
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Cirsium occidentale
Open Interactive Map
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Gladys Lucille Smith  
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Charles Webber  
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Beatrice F. Howitt  
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Gladys Lucille Smith  
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Gerald and Buff Corsi  
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Gerald and Buff Corsi  
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George G. Hawxhurst  
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Beatrice F. Howitt  
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Beatrice F. Howitt  
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The National Science Foundation
Developments of SEINet, Symbiota, and associated specimen databases have been supported by National Science Foundation Grants (DBI 9983132, BRC 0237418, DBI 0743827, DBI 0847966)