Biological Flora of Britain and Ireland: Geranium sylvaticum*: no. 308. [*Nomenclature of vascular plants follows Stace (2019) and, for non-British species, Flora Europaea]

•1. This account presents information on all aspects of the biology of Geranium sylvaticum L. (Wood Crane's‐Bill) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of Britain and Ireland : distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history, conservation and management. •2. Geranium sylvaticum is a perennial forb of woodland, semi‐natural grassland, tall‐herb vegetation, boreal dwarf shrub heaths and subalpine and subarctic scrub. In Britain and Ireland, it occurs in cool and moist northern‐montane climates, in upland hay meadows, road verges, riverbanks, fens and mires, mountain rock ledges, crags and ravines and upland mixed ash forests. •3. Geranium sylvaticum is widespread in Scotland and northern England, with scattered native occurrences in Wales, central England and at the coast of County Antrim, Ireland. It has an extensive native range in Europe and Asia. At the northeastern end of this range, G. sylvaticum can occur down to sea level, whereas in more southern range parts, it is limited to mountain habitats. •4. In Britain and Ireland, Geranium sylvaticum is a species mainly of neutral to moderately calcareous soils of intermediate fertility. In its continental Eurasian range, it also occurs on more acidic soils. •5. Geranium sylvaticum is gynodioecious, that is individual plants are typically female or hermaphrodite. Occasionally, individuals are gynomonoecious, producing both female and hermaphrodite flowers. Female flowers are usually smaller than the protrandrous hermaphrodite flowers. Flowers are visited by insects of the orders Hymenoptera, Diptera and Lepidoptera, as well as Coleoptera and Hemiptera. •6. Primary seed dispersal of G. sylvaticum is ballistic, that is seeds are ejected from fruits. The species has a transient soil seed bank persisting for less than 12 months. The seeds have physical dormancy, that is their seed coat is initially impermeable to water. The species has little capacity for vegetative spread. •7. In Britain and Ireland, G. sylvaticum underwent long‐term distributional decline mostly before 1987. A marked recent increase in records has been observed in northern Scotland, due to either a slight northerly shift in its distribution and/or increased recording in previously underrecorded areas.