Expanded petals and stamens in the wild cornflower Centaurea cyanus (seen from above). This flower head is in fact made up of many lilac-coloured flowers. Petals around the edges are from large sterile flowers. Stamens in the centre are from fertile flowers. Centaurea cyanus is of eastern Mediterranean origin and has lived closely associated with human agriculture since neolithic times. It now is found worldwide among cereal crops, but is disappearing through the use of agricultural herbicides. Leonardo da Vinci once remarked upon the very pure colour of its petals.