Biological flora of Central Europe: Centaurea cyanus L.

Abstract

Centaurea cyanus L., commonly known as cornflower, is an annual plant of the Asteraceae family, probably native to the Eastern Mediterranean region and historically a common weed of cereal crops. It is placed within the genus Centaurea, although the distinction between the genera Centaurea and Cyanus is controversial. C. cyanus has distinctive blue-violet flowers, erect grey-green stems, and lyrate basal leaves. Although its initial distribution was centred in the Eastern Mediterranean region, C. cyanus has spread to Europe, North America, and Asia as a weed. However, intensive farming practices have caused a significant decline in its populations. It grows in various habitats but most frequently in agricultural habitats with nutrient-rich soils and high light availability. It completes its life cycle between winter and spring, showing two distinct emergence periods: one in autumn and one in spring, depending on environmental conditions. C. cyanus has hermaphroditic flowers that are primarily cross-pollinated but can show pseudo-self-compatibility. The plant is pollinated by various insects including bees (Apis mellifera, Bombus spp.), and hoverflies (Syrphidae), which are attracted to its nectar-rich flowers. Its seeds are dispersed by several agents including wind, ants, and mechanical tillage. Seeds show primary dormancy, with optimal germination temperatures between 10 °C and 15 °C. C. cyanus competes poorly with crops and is susceptible to herbivores and pathogens, which can limit its establishment in agricultural fields. However, its association with mycorrhizal fungi plays a beneficial role in soil remediation, enhancing nutrient uptake and improving soil health. C. cyanus contains many secondary compounds including tocopherols, organic and phenolic acids, and anthocyanins with antioxidant and antibacterial activities. C. cyanus is a species of high ecological and genetic relevance. It displays notable within-population genetic diversity, and substantial differentiation among populations, which underlies its adaptive potential across diverse environments. However, the species still faces threats from climate change, habitat degradation, and agricultural practices. It was used in traditional medicine, and has culinary, cosmetic, and ornamental uses. Its conservation status is currently "Least Concern” at the European and European Union levels, but its fragmented distribution, increased inbreeding, declining population trend due to agricultural intensification, high nitrogen inputs, herbicide use, and decreased pollinator activity warrant attention.