plumeless thistles

genus Carduus

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

There are no other wild species of this genus in the bay area.

Key features:

number of heads per cluster
width of involucre
width and hairiness of phyllary bases

italian thistle
Carduus pycnocephalus

italian thistle
Carduus pycnocephalus

generally 2–5 heads per cluster
involucre 1–2 cm diameter
phyllaries generally ≤ 2 mm wide
phyllary bases ± persistently loosely tomentose
very common throughout the bay area

slender thistle
Carduus tenuiflorus

slender thistle
Carduus tenuiflorus

5–20 heads per cluster
involucre 1–2 cm diameter
phyllaries generally ≤ 2 mm wide
phyllary bases glabrous to sparsely tomentose
common throughout the bay area

musk thistle
Carduus nutans

heads generally solitary, conspicuously peduncled
involucre 2–7 cm diameter
phyllaries generally > 2 mm wide
La Honda Creek

2 observed taxons / 1 unobserved taxon / 1 key

Chris’s observations: 29 (16 are research grade)

Locations:

Calero CP: 4
Russian Ridge OSP: 4
Coyote Hills RP: 3
Henry Coe SP: 2
Monte Bello OSP: 2
San Pedro Valley CP: 2
Almaden Quicksilver CP
Coyote Lake / Harvey Bear Ranch CP
Edgewood Park & Natural Preserve
El Corte de Madera OSP
Joseph D. Grant CP
Mt. Diablo SP
Pleasanton Ridge RP
Santa Teresa CP
Sibley Volcanic RP
Sierra Azul; OSP
Stevens Creek CP
Wilder Ranch SP

Months:

Apr.: 7
May: 16
Jun.: 5
Jul.: 0
Aug.: 0
Sep.: 0
Oct.: 0
Nov.: 1

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Taxon info: iNaturalist – Calflora – Jepson eFlora – FNA

Bay Area species: iNaturalist – Calflora