Weeds
Centaurea cyanus L. - Cornflower, Bachelor's Button
Systematic position.
Family Asteraceae, genus Centaurea L.Biological group.
Annual winter weed.Morphology and biology.
Plant 25-100 cm in height. Stalks single, erect, branched, covered with pubescence. Radical and lower leaves long-stalked, early withering, elongate-inversely-lanceolate, blunt at apex. Other leaves lanceolate-linear to narrow-linear, pointed at apex, sessile, with smooth margins. Middle stem leaves are 3-15 mm in length and 0.1-1.2 mm in width, covered sparsely from above and densely from below with hairs. Heads are aggregated in panicle, nearly in cyme. Perianth ovoid, 12-15 mm in length and 5-9 mm in width, with pubescence. Appendages of the lower and middle leaflets are triangular, with short white, silvery, or black-brown fringe along margins. Appendages of the upper leaflets are narrow, brownish, denticulate. Petals of median flowers are blue-violet; petals of marginal flowers are dark blue or blue, less often pink or white; bending lobes of marginal flowers are lanceolate-ovoid. Hemicarp is ellipsoid-obovoid, 3-4.5 mm in length and 1.5-1.8 mm in width. Pappus multiseriate, 3-3.5 mm in length; internal hairs three times shorter than external ones, consisting of narrower cilia. Blossoming in May - October. Seeds have no dormant period, sprout from a depth of 1-6 cm, and maintain germination capacity for 3 years. A single plant is capable of producing 7 thousand seeds.Distribution.
Europe, the Caucasus, Western and Eastern Siberia, the Far East, Central Asia (the south and the east), Minor Asia (the western part), Iran, India (northwest), Northern America, Australia, Africa (the north).Ecology.
Minimal temperature for seed germination is +3 - +5°C, optimum +10 - +12°C. Prefers friable, sandy-loam ground, but grows also on a fine crumbly mixture of clay and limestone soils.Economic significance.
Weed in grain cereals, especially rye, also in fodder grasses, flax, and tilled cultures. Control measures include removing of stubble, autumn plowing, spring harrowing, cleaning of sowing material, pre-sowing treatment of ground, weeding, timely harvest, herbicide treatments (if necessary), and maintenance of crop rotation.Reference citations:
Anon. 1996. Weeds on sugar beet. Berlin: Hoehst Shering AgrEvo Gmbh. 170 pp. (In Russian)Komarov, V.L., ed. 1959. Flora of the USSR. Moscow & Leningrad: AN SSSR. V. 25: 557-558. (In Russian)
Tikhonova Z.E. 1937. Weeds and their control. Gor`kii: Gor'kii Regional Publishing House. 90 pp. (In Russian)
Veselovs'kii I.V., Lisenko A.K., Man'ko Yu.P. 1988. Atlas-synopsis of weeds. Kyiv: Urozhai. 64 pp. (In Ukrainian)