plume thistles

genus Cirsium

Member of thistles
sunflower family (family Asteraceae)
dicots (class Magnoliopsida)
flowering plants (subphylum Angiospermae)

Except for old historical records and extremely rare examples that I don't expect to encounter, there are no other wild species of this genus in the bay area.

Potential key features:

corolla color
head shape
phyllary details, e.g. length, abaxial features, spine tipped or not
leaf details

Purple

bull thistle
Cirsium vulgare

adaxial leaf face with slender appressed bristle-like prickles
[all other species have no prickles on the adaxial leaf face, although they may have hairs]
common

short-styled thistle
Cirsium brevistylum

heads generally closely subtended by ± well-developed distal leaves or clustered bract-like leaves
phyllary tips needle-like, ascending to radially spreading, connected side-to-side by network of cobwebby or multicellular hairs
outer and middle phyllaries with short-appressed bases and lanceolate to linear or needle-like, ascending to stiffly spreading tips; tip-spines generally 1–35 mm
abaxial face of outer and middle phyllaries without sticky-resinous ridge
margins of outer phyllaries may be irregularly toothed to spiny-ciliate or ± entire
corolla lobes thread-like, tips knob-like; style included or exserted 1–2 mm; stem ± hairy, hairs coarse, jointed, generally also cobwebby to densely tomentose with long, fine hairs
scattered

photo

creeping thistle
Cirsium arvense

dioecious
[all other species have both bisexual flowers]
scattered

photo

franciscan thistle
Cirsium andrewsii

abaxial face of outer and middle phyllaries without sticky-resinous ridge
margins of outer phyllaries irregularly toothed to spiny-ciliate
corolla lobes linear, tips not knob-like; style conspicuously exserted; stem cobwebby, ± glabrous in age, coarser, multicellular hairs 0
Marin

photo

swamp thistle
Cirsium douglasii var. douglasii

abaxial face of outer and middle phyllaries with long, sticky-resinous ridge (milky when fresh, dark when dry, occasionally very narrow)
margins of phyllaries entire
stem with few or 0 coarse, multicellular hairs, thinly to densely cobwebby or tomentose with long fine hairs
cauline leaves generally not clasping with expanded basal lobes
leaf veins generally not prominently raised abaxially
Mt. Diablo

photo

mount tamalpais thistle
Cirsium hydrophilum var. vaseyi

abaxial face of outer and middle phyllaries with long, sticky-resinous ridge (milky when fresh, dark when dry, occasionally very narrow)
margins of phyllaries minutely spiny-fringed
Mt. Tam

Red (usually)

cobwebby thistle
Cirsium occidentale

abaxial face of outer and middle phyllaries without sticky-resinous ridge
margins of outer phyllaries ± entire
corolla lobes linear, tips not knob-like; style conspicuously exserted; stem cobwebby to densely tomentose, hairs long, fine
common

Whitish

fountain thistle
Cirsium fontinale

flower heads often drooping
scattered

photo

peregrine thistle
Cirsium cymosum var. cymosum

abaxial face of outer and middle phyllaries may have long, sticky-resinous ridge (milky when fresh, dark when dry, occasionally very narrow) or not
margins of phyllaries entire
outer and middle phyllaries with short-appressed bases and lanceolate to linear or needle-like, ascending to stiffly spreading tips; tip-spines generally 1–35 mm
phyllary tips glabrous or hairy to densely tomentose but generally not conspicuously connected side-to-side by network of cobwebby or multicellular hairs
stem evidently coarse-hairy with multicellular hairs, also cobwebby to densely tomentose with long, fine hairs
cauline leaves generally ± clasping, with expanded basal lobes
leaf veins generally prominently raised abaxially
Henry Coe, Sunol

photo

alameda thistle
Cirsium quercetorum

abaxial face of outer and middle phyllaries without sticky-resinous ridge
margins of outer phyllaries ± entire
outer and middle phyllaries lance-linear to ovate, appressed; tip-spines 1–12 mm, generally ascending to erect
scattered very near the pacific coast

photo

pacific fringed thistle
Cirsium remotifolium var. odontolepis

abaxial face of outer and middle phyllaries without sticky-resinous ridge
margins of outer phyllaries irregularly toothed to spiny-ciliate
heads generally not closely subtended by well-developed distal leaves or clustered leafy bracts
phyllary tips flattened, generally ascending, connected side-to-side by cobwebby hairs or not
Mt. Tam, Briones

4 observed taxons / 11 unobserved taxons / 3 keys

Chris’s observations: 64 (60 are research grade)

Locations:

Henry Coe SP: 4
Sam McDonald CP: 4
Sanborn CP: 4
Máyyan 'Ooyákma Coyote Ridge OSP: 3
Santa Teresa CP: 3
Bear Creek Redwoods OSP: 2
Butano SP: 2
Dr. Aurelia Reinhardt Redwood RP: 2
El Corte de Madera OSP: 2
Monte Bello OSP: 2
Nisene Marks SP: 2
Pescadero Creek CP: 2
Purisima Creek Redwoods OSP: 2
Russian Ridge OSP: 2
San Bruno Mountain State & County Park: 2
Sibley Volcanic RP: 2
Sierra Vista OSP: 2
Wilder Ranch SP: 2
Alpine Rd.
Andrew Molera SP
Castle Rock SP
Coyote Hills RP
Ed R. Levin CP
La Honda Creek OSP
Lake Chabot RP
Long Ridge OSP
McNee Ranch / Montara Mountain SP
Mt. Tamalpais Watershed
Murray Ranch SP
Point Lobos SP
Portola Redwoods SP
San Pedro Valley CP
Sierra Azul OSP
Skyline Ridge OSP
Stevens Creek CP
Sunol Wilderness RP
Sweeney Ridge National Recreation Area
Wunderlich CP

Months:

Mar.: 1
Apr.: 4
May: 6
Jun.: 5
Jul.: 15
Aug.: 19
Sep.: 9
Oct.: 2
Nov.: 2
Dec.: 1

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Taxon info: iNaturalist – Calflora – Jepson eFlora – FNA

Bay Area species: iNaturalist – Calflora