Biological Flora of the British Isles: Crataegus laevigata

Abstract

This account presents information on all aspects of the biology of Crataegus laevigata (Poir.) DC (Midland hawthorn) (C. oxyacanthoides Thuill.) 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, herbivores and disease, history and conservation. Crataegus laevigata is primarily a shade-tolerant shrub or small tree up to 12-m tall of ancient woodlands (of which it is an indicator plant) and occasionally old hedges, usually on heavy clay soils and avoiding limestone and chalk. It is native to central and northern Europe and in the British Isles is native to southeast England, occurring naturally up to the Midlands, hence the common name. It is largely absent naturally from Scotland, Wales and Ireland. Flowers usually have two styles, varying from (rarely) 1 to 5 with an equal number of pyrenes in the fruit, differentiating it from C. monogyna with usually one style and pyrene. Pollination is by insects and fruit are dispersed primarily by birds. Fruit has traditionally been used for food, and with the leaves and flowers have a long tradition in herbal medicine. Disturbance and fragmentation have allowed C. monogyna to permeate into old woodlands and hybridise with C. laevigata. These two species are inter-fertile and barriers to hybridisation are primarily spatial separation thus allowing extensive introgression such that in many parts of Europe, pure C. laevigata is becoming scarce.