Cirsium occidentale |
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cobwebby thistle, snowy thistle, Venus thistle, western thistle |
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Habit | 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. |
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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. |
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Peduncles | 1–30 cm. |
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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. |
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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. |
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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. |
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Heads | 1–many in loose to tight clusters (barely raised above rosette in dwarf plants). |
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Cypselae | ± brown, 5–6 mm, apical collars not differentiated; pappi 15–30 mm. |
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Cirsium occidentale |
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Distribution |
CA; NV; OR
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Discussion | Varieties 7 (7 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 19, p. 137. | ||||||||||||||||||||||||
Parent taxa | |||||||||||||||||||||||||
Sibling taxa | |||||||||||||||||||||||||
Subordinate taxa | |||||||||||||||||||||||||
Synonyms | Carduus occidentalis | ||||||||||||||||||||||||
Name authority | (Nuttall) Jepson: Fl. W. Calif., 509. (1901) | ||||||||||||||||||||||||
Web links |