Centaurea diffusa

Lamarck in J. Lamarck et al.

in J. Lamarck et al., Encycl. 1: 675. 1785.

Common names: Diffuse or tumble or white knapweed centaurée diffuse
Introduced
Synonyms: Acosta diffusa (Lamarck) Soják
Treatment appears in FNA Volume 19. Treatment on page 190. Mentioned on page 183, 194.

Annuals or perennials, 20–80 cm. Stems 1–several, much-branched throughout, puberulent and ± gray tomentose. Leaves hispidulous and ± short-tomentose; basal and proximal cauline petiolate, often absent at anthesis, blades 10–20 cm, margins bipinnately dissected into narrow lobes; mid cauline sessile, bipinnately dissected; distal much smaller, entire or pinnately lobed. Heads disciform, in open paniculiform arrays. Involucres narrowly ovoid or cylindric, 10–13 × 3–5 mm. Principal phyllaries: bodies pale green, ovate to lanceolate, glabrous or finely tomentose, with a few prominent parallel veins, margins and erect appendages fringed with slender stramineous spines, each phyllary tipped by spine 1–3 mm. Inner phyllaries lanceolate, ± acute, appendage lacerate or spine-tipped. Florets 25–35; corollas cream white (rarely pink or pale-purple), those of sterile florets 12–13 mm, slender, inconspicuous, those of fertile florets 12–13 mm. Cypselae dark-brown, ca. 2–3 mm; pappi 0 or less than 0.5 mm, only rudimentary. 2n = 18, 36.


Phenology: Flowering summer (Jun–Aug).
Habitat: Disturbed sites in grasslands, woodlands, open coniferous forests
Elevation: 100–2200 m

Distribution

V19-218-distribution-map.gif

Introduced; Alta., B.C., Ont., Que., Sask., Yukon, Ariz., Calif., Colo., Conn., Idaho, Ill., Ind., Iowa, Ky., Mass., Mich., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., Oreg., R.I., Tenn., Utah, Wash., Wyo., Europe

Discussion

Centaurea diffusa is native to southeastern Europe and casually adventive in central and western Europe.

Centaurea diffusa readily hybridizes with C. stoebe subsp. micranthos and is often confused with their fertile hybrid (C. ×psammogena G. Gáyer); the latter can be recognized by its cypselae bearing pappi and having conspicuously radiant heads. Morphologically the hybrids are extremely variable; they may be intermediate or may closely resemble one or the other of the parents. Conspicuously radiant heads and pappi are always present; appendages of the phyllaries are brown to black, or rarely stramineous; spines are absent or short and 2n = 18. Centaurea ×psammogena is known from waste places, roadsides, railway tracks; 50–2500 m; B.C., Ont., Que.; Colo., Mass., Mich., Mo., N.C., Oreg., Tenn., Wash. It may occur spontaneously where the ranges of the parent species overlap; they may also be distributed separately. In mixed stands it replaces C. diffusa by introgression. Hybrids are often misidentified as C. diffusa.

Selected References

None.

Lower Taxa

None.

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

... more about "Centaurea diffusa"
with fine , 1-celled hairs +  and glabrous +
scarious +
spine-tipped +, lacerate +  and fringed +
paniculiform +  and open +
indeterminate +  and determinate +
David J. Keil +  and Jörg Ochsmann +
Lamarck in J. Lamarck et al. +
decurrent +
Asteraceae tribe Cynareae +
compound +  and simple +
10 cm100 mm <br />0.1 m <br /> (20 cm200 mm <br />0.2 m <br />) +
pale green +
tomentose +  and glabrous +
10-nerved or 20-nerved +  and rugose +
ovate;lanceolate +
barbed +  and smooth +
Diffuse or tumble or white knapweed +  and centaurée diffuse +
actinomorphic +
radial +  and bilateral +
white +  and blue pink purple or yellow +
inconspicuous +
expanded +  and slender +
compressed +  and barrel--shaped +
fertile +  and bisexual +
lobed +  and entire +
Alta. +, B.C. +, Ont. +, Que. +, Sask. +, Yukon +, Ariz. +, Calif. +, Colo. +, Conn. +, Idaho +, Ill. +, Ind. +, Iowa +, Ky. +, Mass. +, Mich. +, Mo. +, Mont. +, Nebr. +, Nev. +, N.H. +, N.J. +, N.Mex. +, Oreg. +, R.I. +, Tenn. +, Utah +, Wash. +, Wyo. +  and Europe +
100–2200 m +
glandular-punctate +
puberulent +, strigose +, villous +, tomentose +  and glabrous +
pistillate +, staminate +  and neuter +
1.2 cm12 mm <br />0.012 m <br /> (1.3 cm13 mm <br />0.013 m <br />) +
fertile +  and sterile +
winged +  and beaked +
dispersed +
Disturbed sites in grasslands, woodlands, open coniferous forests +
in corymbiform arrays +, singly +  and radiant +
indeterminate +
each +  and sessile +
1 cm10 mm <br />0.01 m <br /> (1.3 cm13 mm <br />0.013 m <br />) +
cylindric;ovoid +
0.3 cm3 mm <br />0.003 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
sessile +  and petiolate +
cauline +  and basal +
short-tomentose +  and hispidulous +
acute +  and linear-oblong +
entire +  and dentate +
cauline +  and mid +
fringed +  and dissected +
2-carpellate +
persistent +
rudimentary +
0.5 cm5 mm <br />0.005 m <br /> (?) +
Flowering summer (Jun–Aug). +
papillate +  and smooth +
distinct +  and fused +
in J. Lamarck et al., Encycl. +
flat;convex +
exalbuminous +
Introduced +
0.1 cm1 mm <br />0.001 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
much-branched +
spreading +, ascending +  and erect +
1 +  and several +
appendaged +  and truncate +
dilated +  and swollen +
enlarged +
Acosta diffusa +
Centaurea diffusa +
Centaurea +
species +
perennial +  and annual +
tomentose +  and glabrous +
20 cm200 mm <br />0.2 m <br /> (80 cm800 mm <br />0.8 m <br />) +
tree +, vine +, shrub +  and subshrub +
15 +, 13 +, 12 +, 11 +, 10 +, 9 +  and 8 +