Biological Flora of the British Isles: Campanula rotundifolia

Summary1. This account presents information on all aspects of the biology of Campanula rotundifolia L. that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivory and disease, history, and conservation.2. Campanula rotundifolia is a slender, rhizomatous, prostrate to erect herb with long-stalked roundish basal leaves, linear stem leaves, and a blue, bell-shaped corolla. It is widespread in the British Isles though absent from parts of Ireland. Globally, C. rotundifolia has a circumpolar distribution extending from the Arctic Circle to northern Mexico and North Africa. It forms a polyploid complex with some characters linked to ploidy level. Populations in the British Isles are predominantly tetraploid and hexaploid, with occasional pentaploids. The distribution of these cytotypes in the British Isles has a strong spatial structure.3. Campanula rotundifolia has a wide ecological amplitude, tolerating very dry conditions but also occasionally occurring in permanently saturated habitats, and it grows on a very wide range of soil types, from coarse sands through loams to heavy clays and pure peats. However, C. rotundifolia is rarely found on fertile lowland clays where competition from more vigorous species may limit growth. Campanula rotundifolia is found in a range of grassland, heath, mire, scrub and sand dune communities spanning a wide range of soil pH.4. Campanula rotundifolia is perennial and spreads by seed and by rhizome. Plants generally overwinter as frost-resistant green rosettes. As the spring season progresses, plants make slow vegetative growth. Erect flowering stems develop from June onwards. Campanula rotundifolia is largely self-incompatible, and is insect pollinated, regularly producing large quantities of viable seed.5. Although C. rotundifolia is a widespread and locally very common species there is some evidence from Britain and across Europe that it is in decline. These losses are likely to be due to a number of factors including agricultural intensification, reversion of grassland to scrub and woodland, disturbance, and atmospheric pollution.