Jepson Flora Project: Jepson Interchange    

 
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Jepson Interchange (more information)
©Copyright 1993 by the Regents of the University of California

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  • Up-to-date information about California vascular plants is available from the Jepson eFlora.

ASTERACEAE

SUNFLOWER FAMILY

David J. Keil, Family Editor and author, except as specified

Annual to tree
Leaves basal or cauline, alternate to whorled, simple to compound
Inflorescence: 1° inflorescence a head, each resembling a flower, 1–many, generally arrayed in cymes, generally subtended by ± calyx-like involucre; flowers 1–many per head
Flowers bisexual, unisexual, or sterile, ± small, of several types; calyx 0 or modified into pappus of bristles, scales, or awns, which is generally persistent in fruit; corolla radial or bilateral (rarely 0), lobes generally (0)4–5; stamens 4–5, anthers generally fused into cylinder around style, often appendaged at tips, bases, or both, filaments generally free, generally attached to corolla near throat; pistil 1, ovary inferior, 1-chambered, 1-seeded, style 1, branches 2, generally hair-tufted at tip, stigmas 2, generally on inside of style branches
Fruit: achene, cylindric to ovoid, generally deciduous with pappus attached
Genera in family: ± 1300 genera, 21,000 species (largest family of dicots): worldwide. Largest family in CA. Also see tribal key to CA genera: Strother 1997 Madroño 44(1):1–28. See glossary p. 25 for illustrations of general family characteristics.

CIRSIUM

THISTLE

David J. Keil and Charles E. Turner

Annual to perennial herb (sometimes short-lived, dying after flowering once)
Stem generally erect
Leaves: lower generally tapered or petioled, often wavy-margined, generally pinnately lobed, ± dentate, lobes and teeth spine-tipped, margin generally spiny-ciliate, glabrous to tomentose; upper generally sessile, ± reduced
Inflorescence: heads discoid, 1–many; involucre cylindric to spheric; phyllaries many, graduated in several series, outer spine-tipped; receptacle flat, long-bristly
Flowers generally many; corollas ± bilateral, white to red or purple, tube long, slender, lobes linear; anther bases sharply sagittate, tips oblong; style tip with slightly swollen node, appendage (above node) long, cylindric, branches very short
Fruit ovoid, glabrous; scar slightly angled; pappus bristles many, plumose, ± persistent or falling in ring
Species in genus: ± 200 species: North America, Eurasia
Etymology: (Greek: thistle)
Taxa difficult, incompletely differentiated, hybridize.

Native

C. occidentale (Nutt.) Jeps.

Biennial 1–30 dm, erect or low, mound-like
Stem generally 1, branched above (near base in dwarf plants), ± tomentose
Leaves ± densely gray- or whitish tomentose, especially below; lower 1–4 dm, petioles spiny-winged, blade oblanceolate, lobed 1/2+ to midvein, lobes widely triangular, dentate or further lobed, main spines 1–10 mm; upper gradually reduced, sessile, ± clasping or short-decurrent, linear or oblong, often entire, often spinier than lower, uppermost bract-like
Inflorescence: heads 1–several in loose to tight cluster (barely raised above rosette in dwarf plants); peduncles 1–30 cm; involucres 1.5–5 cm, 1.5–8 cm diam, ovoid to spheric; phyllaries ± equal to strongly graduated, linear or linear-lanceolate, straight, ascending and appressed to widely radiating, often connected side-to-side by conspicuous cobwebby hairs, spines 3–10+ mm, inner with tips flat, straight
Flowers: corollas 18–40 mm, white to purple or red, tube 8–18 mm, throat 5–7 mm, lobes 5–10 mm
Fruit 5–6 mm, shiny, ± brown; pappus 15–30 mm
Chromosomes: 2n=30
Ecology: Many habitats
Elevation: < 3600 m.
Bioregional distribution: California Floristic Province (except San Joaquin Valley), Modoc Plateau, White and Inyo Mountains, w Mojave Desert
Distribution outside California: to s Oregon, sw Idaho, w Nevada
Variable; ± distinctive, intergrading races often treated as sp.

Native

var. compactum Hoover

COMPACT COBWEBBY THISTLE

Plants generally 0.5–3 dm, low, mound-like
Inflorescence: heads short-peduncled, closely subtended by basal and large cauline leaves; involucre 5–8 cm diam, densely cobwebby; middle phyllary tips generally 1–2 cm, generally 1–2 mm wide, straight, ± spreading
Flowers: corollas 25–30 mm, dark rose-purple
Chromosomes: 2n=30
Ecology: Bluffs
Elevation: < 50 m.
Bioregional distribution: Central Coast (n San Luis Obispo, Monterey cos., formerly San Francisco).Some inland plants suggest weak separation from var. occidentale
Horticultural information: In cultivation.
See the CNPS Inventory for information about endangerment and rarity.
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bioregional map for CIRSIUM%20occidentale%20var.%20compactum being generated
 


Retrieve Jepson Interchange Index to Plant Names entry for Cirsium occidentale var. compactum
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