Sunday, January 29, 2017

Cirsium scariosum (Elk Thistle)

7/9/16 Hwy. 108 (Sonora Pass Highway), 
Humboldt-Toiyabe National Forest, Sierra Nevada range, Tuolumne County, CA



5/19/17 William Heise County Park, Laguna Mountains, San Diego County, CA


COMMON NAME: Elk Thistle

SPECIES: Cirsium scariosum

FAMILY: Asteraceae (Sunflower Family)

LIFE LIST DATE: 7/9/2016

LOCATION: Hwy. 108 (Sonora Pass Highway), Humboldt-Toiyabe National Forest, Sierra Nevada range, Tuolumne County, CA


Treatment from Jepson eFlora:

Habit: Biennial or short-lived perennial herb, 0.5--10+ dm. 

Stem: often 0 or short, occasionally erect or bushy-branched, often +- fleshy, glabrous to loosely tomentose, occasionally coarse-hairy. 

Leaf: glabrous to loosely tomentose adaxially, glabrous to densely tomentose abaxially; often all basal, +- petioled, cauline 0 or well distributed, proximal 1--4 dm, tapered or spiny-petioled, oblong to oblanceolate, unlobed to deeply lobed, occasionally with 2° lobes or teeth, main spines 2--10+ mm. 

Inflorescence: heads generally crowded, +- sessile, closely subtended by basal rosette or in +- tight, generally leafy clusters at stem tips; involucre 2--4.5 cm, 2--5 cm diam, ovoid to bell-shaped, glabrous; outer phyllaries lance-linear to ovate, +- entire, tip-spine 1--12 mm, ascending, inner tips narrow and entire or expanded and irregularly toothed or cut, flat or crinkled. 

Flower: corolla 20--40 mm, +- white to purple, tube 7--24 mm, throat 4--12 mm, lobes 4--10 mm; style tip 3.5--8 mm. 

Fruit: 3--6.5 mm; pappus 15--35 mm. 

Note: Variable complex of intergrading races. Extreme forms very different. Stemmed or stemless forms may occur in same population or not. Some plants not readily assignable to variety. Needs study. 

Unabridged Note: Past taxonomic treatments have variably recognized members of this complex as multiple species, some as subspecies and/or varieties or have merged all or most variants into a single polymorphic sp. with extraordinary variability. See Keil 2006 for discussion. Hybrids are known or suspected in many cases where forms of Cirsium scariosum meet other native thistle species. Unusual variants in herbaria may represent unrecognized hybrids or their descendants.

eFlora Treatment Author: David J. Keil

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