Centaurea Cyanus “Blue Boy” is a well known annual plantCentaurea Cyanus “Blue Boy” is a well known annual plantthat has large double deep blue flowers and can grow toa height of 80cm, is very showy for garden displays orwonderful as a cut flower.They will thrive in almost any well prepared soil that has notbeen over fertilised.Although seeds may be sown in a seed tray and transplantedto the open garden, better results will be obtained by sowingseeds directly in ground and later thinning out to 30cmapart.