The genus Crataegus is native to the northern temperate regions of Europe, Asia and North America. It comprises some 250 species of shrubs or small trees. Many are armed with thorns derived from sharp-tipped branches. Some authorities consider the number of species to be many times greater than this. Disagreements over numbers of Crataegus species are frequently associated with the relative importance attached to patterns of intraspecific morphological variation, breeding system variation and the frequency of interspecific hybridisation.
In the United Kingdom, two species Crataegus species, Crataegus monogyna and Crataegus laevigata, are native. However, complex patterns of variation mean that it can be difficult to separate them in some parts of their ranges. The latest account of British hawthorns makes the point that such patterns may be far more complex than previously thought because of the many species that have been introduced for horticultural, forestry and amenity purposes.
Hedges are an obvious landscape feature of rural Britain and northern France. Hawthorns are the primary trees used in hedges; a word derived from an Anglo-Saxon term meaning a 'fence with thorns'. When well-managed, using techniques such as laying, hawthorn will produce a thick, stock-resistant hedge. Moreover, hawthorns have other important ecosystem functions. They are shelter and protection for animals, and nesting habitat. The flowers, which are produced in late spring, provide nectar and pollen for the main pollinators, od hawthorn, flies and bees. The fruits (haws) are valuable food for birds, which are important as seed dispersers.
The haw, which looks superficially like a berry, is technically called a pome; it is like an apple. In the haw's centre there are one to five bony pyrenes each surrounding a seed. The fruits of various Crataegus species are eaten by humans. More recently, evidence has emerged that there may be a scientific basis for the traditional use of Crataegus fruits and leaves in cardiovascular conditions.
One interpretation of the generic name Crataegus is from the Greek meaning 'sharp strength', and appears to be a reference to hardness of hawthorn wood. Hawthorns have rich folkloric associations across Europe. The Glastonbury thorn (Crataegus monogyna 'Biflora'), a mutant that flowers in early winter and spring, was believed to have grown from a staff planted by Joseph of Arimathea at Glastonbury. Scions of this tree have been popular in gardens since the early seventeenth century. Other mythologies associate the hawthorn with fairies and protection from lightning.
Sell P and Murrell G 2014. Flora of Great Britain and Ireland. Vol. 2. Capparaceae-Rosaceae. Cambridge University Press.
Tassell M et al. 2010. Hawthorn (Crataegus spp.) in the treatment of cardiovascular disease. Pharmacognosy Reviews 4: 32-41.
Vaughn B 2015. Hawthorn. The tree that has nourished, healed, and inspired through the ages. Yale University Press.