Acroptilon repens

(Linnaeus) de Candolle in A. P. de Candolle and A. L. P. P. de Candolle

in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 6: 663. 1838.

IntroducedIllustrated
Basionyms: Centaurea repens Linnaeus Sp. Pl. ed. 2, 2: 1293. 1763
Synonyms: Acroptilon picris (Pallas ex Willdenow) C. A. Meyer C. picris Pallas ex Willdenow
Treatment appears in FNA Volume 19. Treatment on page 172.

Creeping roots usually dark-brown or black, with scaly adventitious-buds. Stems ± cobwebby-tomentose. Leaves: basal and proximal cauline often deciduous by flowering, blades oblong, 4–15 cm; mid and distal linear to linear-lanceolate or oblong, 1–7 cm. Involucres 9–17 mm, loosely cobwebby. Phyllaries: apices of inner acute or acuminate, densely short-pilose. Corollas 11–14 mm, tubes 6.5–7.5 mm, throats 2–3.5 mm, lobes 3–3.5 mm. Cypselae ivory to grayish or brown, 2–4 mm; pappus bristles white, 6–11 mm. 2n = 26.


Phenology: Flowering late spring–summer (May–Sep).
Habitat: Fields, roadsides, riverbanks, ditch banks, clearcuts, cultivated ground
Elevation: 0–2300 m

Distribution

V19-188-distribution-map.gif

Introduced; Alta., B.C., Man., Ont., Sask., Ariz., Calif., Colo., Idaho, Iowa, Kans., Minn., Mont., Nebr., Nev., N.Mex., N.Dak., Okla., Oreg., S.Dak., Tex., Utah, Wash., Wyo., Mexico (Baja California), c Asia

Discussion

Acroptilon repens has been reported also from Arkansas, Illinois, Indiana, Kentucky, Louisiana, Michigan, Missouri, New York, Ohio, Virginia, and Wisconsin; I have not seen specimens from those states.

Acroptilon repens is a serious weed pest, especially in the western United States. It is a strong competitor in infested areas, often forming dense colonies, and has allelopathic effects on other plants growing nearby. It is very difficult to control or eradicate once it becomes established. It reproduces vigorously from seed and spreads from adventitious buds borne on deep-seated runner roots. Root fragments readily regenerate as new individuals after cultivation. In addition, Russian knapweed is very poisonous to horses, causing neurological symptoms. Because of its bitter taste, it is usually avoided by grazing animals, and consequently it tends to spread when more palatable plants are consumed.

Selected References

None.

Lower Taxa

None.

"fine" is not a number.

... more about "Acroptilon repens"
short-tailed +
short-pilose +
scarious +
paniculiform +  and corymbiform +
indeterminate +  and determinate +
David J. Keil +
(Linnaeus) de Candolle in A. P. de Candolle and A. L. P. P. de Candolle +
decurrent +
Centaurea repens +
compound +  and simple +
lobed +  and dentate +
4 cm40 mm <br />0.04 m <br /> (15 cm150 mm <br />0.15 m <br />) +
10-nerved or 20-nerved +  and rugose +
actinomorphic +
white +, pink +  and blue +
1.1 cm11 mm <br />0.011 m <br /> (1.4 cm14 mm <br />0.014 m <br />) +
with indistinct ribs +  and smooth +
ivory +  and grayish or brown +
compressed +  and obovoid +
fertile +  and bisexual +
Alta. +, B.C. +, Man. +, Ont. +, Sask. +, Ariz. +, Calif. +, Colo. +, Idaho +, Iowa +, Kans. +, Minn. +, Mont. +, Nebr. +, Nev. +, N.Mex. +, N.Dak. +, Okla. +, Oreg. +, S.Dak. +, Tex. +, Utah +, Wash. +, Wyo. +, Mexico (Baja California) +  and c Asia +
0–2300 m +
resin-gland-dotted +, puberulent +, glabrate +  and tomentose +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Fields, roadsides, riverbanks, ditch banks, clearcuts, cultivated ground +
in corymbiform , paniculiform or racemiform , arrays +  and singly +
indeterminate +
each +  and sessile +
0.6 cm6 mm <br />0.006 m <br /> (1 cm10 mm <br />0.01 m <br />) +
ovoid;subspheric +
constricted +
0.9 cm9 mm <br />0.009 m <br /> (1.7 cm17 mm <br />0.017 m <br />) +
petiolate +  and sessile +
cauline +  and basal +
deltate +, usually narrowly triangular +  and more or less linear +
usually lobed +  and dissected +
linear +  and linear-lanceolate or oblong +
1 cm10 mm <br />0.01 m <br /> (7 cm70 mm <br />0.07 m <br />) +
round +  and ovate +
2-carpellate +
0.6 cm6 mm <br />0.006 m <br /> (1.1 cm11 mm <br />0.011 m <br />) +
persistent +
Flowering late spring–summer (May–Sep). +
papillate +  and smooth +
distinct +  and fused +
papillate +
in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. +
bearing subulate enations +, hairy +  and bristly +
flat;convex +
indistinct +
black +  and dark-brown +
setiform +
unequal +
exalbuminous +
Introduced +  and Illustrated +
appendaged +  and truncate +
dilated +  and swollen +
enlarged +
Acroptilon picris +  and C. picris +
Acroptilon repens +
Acroptilon +
species +
expanded +
0.2 cm2 mm <br />0.002 m <br /> (0.35 cm3.5 mm <br />0.0035 m <br />) +
slender +
0.65 cm6.5 mm <br />0.0065 m <br /> (0.75 cm7.5 mm <br />0.0075 m <br />) +
entire +, dentate +  and not spiny +
30 cm300 mm <br />0.3 m <br /> (100 cm1,000 mm <br />1 m <br />) +
tree +, vine +, shrub +  and subshrub +