Flower strips in agricultural landscapes are planted to counteract an ongoing loss of biodiversity. However, there is still much room for improvement. Based on the findings of a research project, this paper shows how flower strips can be optimised and thus increase the diversity of flower-visiting insect species. The common use of standard seed mixtures comprising plant species that are not adapted to local conditions presents a risk that many plant species do not establish - especially under unfavourable weather conditions in spring. In addition, neophytes and cultivated species often used in standard seed mixtures predominantly support ubiquitous insect species, whereas native and site-adapted segetal species interact with both ubiquitous and specialised flower visitors and thus support a particularly broad range of insect species. Species-rich seed mixtures of site-adapted plant species (preferably of regional origin) could contribute much better to segetal and insect species conservation in agricultural landscapes.