International Biological Flora: Loranthus europaeus *

Abstract This account presents information on all aspects of the biology of Loranthus europaeus Jacq. (vernacular names: yellow mistletoe; yellow‐berried mistletoe) (synonyms: Hyphear europaeum (Jacq.) Danser; Loranthus dioicus Stokes; Viscum guernum Rchb.) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the International Biological Flora : distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation. Loranthus europaeus is a deciduous hemiparasite primarily infesting oaks ( Quercus spp.), although it can parasitize other deciduous trees. Its haustoria form direct xylem connections with host trees, enabling the uptake of water and minerals. Heavy infestations can reduce host growth and vitality and increase mortality. The plant exhibits high transpiration and low water‐use efficiency, which exacerbates host stress, particularly under drought conditions. The species is dioecious, with individual plants bearing either male or female flowers, and its seeds are dispersed by birds, especially thrushes. The fruits are sticky berries that adhere to the branches or trunks of the host. Germination and haustorial development depend on light and physical contact with the host. Distribution is influenced by climate, host availability and dispersal vectors. Loranthus europaeus is distributed across southern, central and eastern Europe, with isolated populations in western Asia and western Europe, including the United Kingdom. It prefers sun‐exposed positions within the host crown. The species not only plays an important ecological role, supporting biodiversity, but also poses a threat to forest health. Biochemically, it is rich in flavonoids, essential oils and fatty acids with potential medicinal applications. Traditionally used in folk medicine, it is now being studied for its antimicrobial, antioxidant and anti‐inflammatory properties.