Carduus tenuiflorus

Curtis

Fl. Londin. 2(6,61): plate 55. 1789.

Common names: Slender-flowered thistle
Introduced
Synonyms: Carduus pycnocephalus var. tenuiflorus (Curtis) Fiori
Treatment appears in FNA Volume 19. Treatment on page 94. Mentioned on page 91.

Annuals, 20–200 cm. Stems simple or openly branched, loosely tomentose with fine single-celled hairs and villous with curled, septate hairs; teeth of wings to 25 mm, wing spines to 15 mm. Leaves: basal tapered to winged petioles, blades 10–25 cm, margins pinnately 6–10-lobed, abaxial faces tomentose, adaxial faces loosely tomentose and villous or ± glabrate; cauline sessile, shorter, less divided. Heads clustered in ± tight arrays of 5–20+ at ends of stems, usually sessile, 15–22 mm × 7–12 mm. Involucres cylindric to ellipsoid (appearing campanulate when pressed), 15–20 × 7–12 mm. Phyllaries linear-lanceolate, bases appressed, 2–2.5 mm wide, ± glabrate, and ascending, appendages 0.5–1.5 mm wide, narrowly scarious-margined, distally glabrous or minutely ciliolate, spine tips 1–2 mm, inner phyllaries with erect, straight, unarmed tips. Corollas pinkish, 10–14 mm; lobes 1.5–2.5 times longer than throat. Cypselae brown, 4–5 mm, finely 10–13-nerved; pappus bristles 10–15 mm. 2n = 54.


Phenology: Flowering spring–early summer (Apr–Jul).
Habitat: Aggressive weed of waste ground, pastures, roadsides, fields
Elevation: 0–1000 m

Distribution

V19-50-distribution-map.gif

Introduced; Calif., Oreg., Pa., s Europe (Mediterranean region)

Discussion

Carduus tenuiflorus has been reported from New Jersey, Texas, and Washington; I have not seen specimens from those states.

Carduus pycnocephalus and C. tenuiflorus are similar annuals with small, usually tightly clustered heads. The number of heads per capitulescence is usually ultimately greater in C. tenuiflorus, but early season plants of this species often have only a few heads. At the end of the growing season the fruiting heads of C. tenuiflorus are aggregated in dense, subspheric clusters. Stem wings tend to be more pronounced in C. tenuiflorus. Fresh corollas of C. pycnocephalus are rose-purple whereas those of C. tenuiflorus have a more pinkish tinge, but this difference is subtle and not reliable on herbarium material. The phyllaries of C. tenuiflorus are membranous-margined, more or less glabrate, and lack the short, stiff, upwardly appressed trichomes of C. pycnocephalus. All published chromosome counts for Carduus tenuiflorus from both Old and New World material are the same.

The two species sometimes grow in mixed populations and at times appear to intergrade. Hybridization has been reported in Europe (S. W. T. Batra et al. 1981) and is suspected to occur in California. Hybrids between C. pycnocephalus and C. tenuiflorus have been designated Carduus ×theriotii Rouy.

Selected References

None.

Lower Taxa

None.

"fine" is not a number."fine" is not a number.

... more about "Carduus tenuiflorus"
glabrate +, villous +  and tomentose +
short-tailed +
ascending +  and spreading or reflexed +
scarious +
scarious-margined +
ciliolate +  and glabrous +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
racemiform +, paniculiform +  and corymbiform +
indeterminate +  and determinate +
David J. Keil +
Curtis +
decurrent +
2mm;2.5mm +
Asteraceae tribe Cynareae +
compound +  and simple +
10 cm100 mm <br />0.1 m <br /> (25 cm250 mm <br />0.25 m <br />) +
10-nerved or 20-nerved +  and rugose +
Slender-flowered thistle +
actinomorphic +
1 cm10 mm <br />0.01 m <br /> (1.4 cm14 mm <br />0.014 m <br />) +
compressed +  and ovoid +
fertile +  and bisexual +
Calif. +, Oreg. +, Pa. +  and s Europe (Mediterranean region) +
0–1000 m +
glabrous +  and hairy +
pistillate +, staminate +  and neuter +
several;many +
winged +  and beaked +
dispersed +
Aggressive weed of waste ground, pastures, roadsides, fields +
septate +  and single-celled +
indeterminate +
1.5 cm15 mm <br />0.015 m <br /> (2.2 cm22 mm <br />0.022 m <br />) +
0.7 cm7 mm <br />0.007 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
each +  and sessile +
1.5 cm15 mm <br />0.015 m <br /> (2 cm20 mm <br />0.02 m <br />) +
cylindric;ellipsoid +
0.7 cm7 mm <br />0.007 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
sessile +  and petiolate +
cauline +  and basal +
1.5-2.5 times longer than throat +
deltate +, usually narrowly triangular +  and more or less linear +
6-10-lobed +
2-carpellate +
1 cm10 mm <br />0.01 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
persistent +
Flowering spring–early summer (Apr–Jul). +
papillate +  and smooth +
distinct +  and fused +
Fl. Londin. +
bearing subulate enations +, hairy +  and bristly +
flat;convex +
setiform +
exalbuminous +
Introduced +
0.1 cm1 mm <br />0.001 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
branched +  and simple +
appendaged +  and truncate +
dilated +  and swollen +
enlarged +
Carduus pycnocephalus var. tenuiflorus +
Carduus tenuiflorus +
species +
campanulate +
expanded +
straight +
slender +
200 cm2,000 mm <br />2 m <br /> (400 cm4,000 mm <br />4 m <br />) +
glabrate +  and tomentose +
20 cm200 mm <br />0.2 m <br /> (200 cm2,000 mm <br />2 m <br />) +
tree +, vine +, shrub +  and subshrub +
0 cm0 mm <br />0 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
13 +, 11 +, 10 +, 9 +  and 8 +