Centaurea virgata subsp. squarrosa

(Boissier) Gugler

Ann. Hist.-Nat. Mus. Natl. Hung. 6: 248. 1908.

Common names: Squarrose knapweed
WeedyIntroduced
Basionym: Centaurea virgata var. squarrosa Boissier Fl. Orient. 3: 651. 1875,
Treatment appears in FNA Volume 19. Treatment on page 191.

Perennials, 20–50 cm, scabrous. Stems several, diffusely much-branched distally, finely tomentose, minutely resin-gland-dotted. Leaves finely tomentose, minutely resin-gland-dotted; basal and proximal cauline petiolate, often absent at anthesis, blades 10–15 cm, margins 1–2 times pinnately divided into linear segments; mid and distal cauline sessile, smaller, pinnately divided or simple. Heads disciform, in paniculiform arrays, sessile or short-pedunculate. Involucres narrowly ovoid or cylindric, 7–8 × 3–5 mm, falling at maturity with enclosed cypselae. Principal phyllaries: bodies pale green or stramineous, ovate to lanceolate, sometimes purple-tinged, glabrous or finely tomentose, sparsely resin-gland-dotted, margins scarious, appendages spreading, fringed with slender stramineous spines, each tipped by spreading to reflexed spine 1–3 mm. Inner phyllaries lanceolate, ± acute. Florets 10–14 (–16); corollas pink or pale-purple, those of sterile florets very slender, 3-lobed, linear, not exceeding disc corollas, those of fertile florets 7–9 mm. Cypselae light-brown or stramineous, 2.5–3.5 mm, glabrous; pappi of white bristles 1–2.5 mm or sometimes very reduced. 2n = 36.


Phenology: Flowering summer (Jun–Sep).
Habitat: Rangelands, pastures, open forests, roadsides
Elevation: 1000–2000 m

Distribution

V19-220-distribution-map.gif

Introduced; Calif., Colo., Mich., Nev., Oreg., Utah, Wyo., w Asia

Discussion

Squarrose knapweed is an invasive pest in rangelands of western North America. At maturity the fruiting heads readily fall from the plant and can become lodged in the fur of animals. Centaurea virgata subsp. squarrosa has been declared a noxious weed in several western states.

In the Synthesis of the North American Flora (J. T. Kartesz and C. A. Meacham 1999) Centaurea virgata is incorrectly listed as a synonym of C. triumfettii Allioni, a very different plant. This was apparently based on a misreading of C. variegata Lamarck (not a legitimate name), a synonym of C. triumfettii, as C. virgata.

Selected References

None.

Lower Taxa

None.

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

with fine , 1-celled hairs +  and glabrous +
scarious +
paniculiform +
indeterminate +  and determinate +
David J. Keil +  and Jörg Ochsmann +
(Boissier) Gugler +
decurrent +
Centaurea virgata var. squarrosa +
compound +  and simple +
10 cm100 mm <br />0.1 m <br /> (15 cm150 mm <br />0.15 m <br />) +
purple-tinged +, stramineous +  and pale green +
resin-gland-dotted +, tomentose +  and glabrous +
10-nerved or 20-nerved +  and rugose +
ovate;lanceolate +
barbed +  and smooth +
0.1 cm1 mm <br />0.001 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
Squarrose knapweed +
actinomorphic +
radial +  and bilateral +
white +  and blue pink purple or yellow +
inconspicuous +
expanded +  and slender +
stramineous +  and light-brown +
compressed +  and barrel--shaped +
fertile +  and bisexual +
Calif. +, Colo. +, Mich. +, Nev. +, Oreg. +, Utah +, Wyo. +  and w Asia +
1000–2000 m +
glandular-punctate +
puberulent +, strigose +, villous +, tomentose +  and glabrous +
pistillate +, staminate +  and neuter +
pale-purple +  and pink +
0.7 cm7 mm <br />0.007 m <br /> (0.9 cm9 mm <br />0.009 m <br />) +
fertile +  and sterile +
winged +  and beaked +
dispersed +
Rangelands, pastures, open forests, roadsides +
short-pedunculate +  and sessile +
in corymbiform arrays +, singly +  and radiant +
indeterminate +
each +  and sessile +
0.7 cm7 mm <br />0.007 m <br /> (0.8 cm8 mm <br />0.008 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 +
resin-gland-dotted +  and tomentose +
acute +  and linear-oblong +
simple +  and sessile +
entire +  and dentate +
cauline +  and mid +
smaller +
1-2 times pinnately divided into linear segments +
2-carpellate +
persistent +
reduced +
Flowering summer (Jun–Sep). +
papillate +  and smooth +
distinct +  and fused +
Ann. Hist.-Nat. Mus. Natl. Hung. +
flat;convex +
exalbuminous +
Weedy +  and Introduced +
spreading +  and reflexed +
0.1 cm1 mm <br />0.001 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
much-branched +
spreading +, ascending +  and erect +
appendaged +  and truncate +
dilated +  and swollen +
enlarged +
Acosta +, Cnicus +, Grossheimia +, Jacea +  and Leucacantha +
Centaurea virgata subsp. squarrosa +
Centaurea virgata +
subspecies +
tomentose +  and glabrous +
20 cm200 mm <br />0.2 m <br /> (50 cm500 mm <br />0.5 m <br />) +
tree +, vine +, shrub +  and subshrub +
15 +, 13 +, 12 +, 11 +, 10 +, 9 +  and 8 +