Common Hawthorn

This week, I decided to look into a tree that is ubiquitous across the British countryside, and occurs in the woodland around the UEA lake: Common hawthorn.

Growing up to around 15m tall, the Hawthorn tree (Crataegus monogyna), also commonly known as the May tree or Mayblossom, is a deciduous tree native to the UK. The leaves of the Hawthorn tree are simple with serrated lobes, and around 6cm long, turning yellow in the autumn before dropping off. Hawthorn bark is a dull brown-grey. Its white (occasionally pink) flowers grow in clusters and are approximately 1cm across, with 5 petals. The flowers are hermaphroditic, meaning they have both male a female parts. After pollination, the flowers develop into red fruits known as haws. These appear berry-like but are structurally pomes - simple fleshy fruits with most the flesh from a receptacle around the ovary. 

Hawthorn blossom

This species is widespread across the UK, and is classified as 'least concern' by the IUCN. It grows well in most soils, although non-acidic soils are generally preferable. Hawthorn is common in open and edge woodland, scrub and hedgerows; as the dominant hedgerow species in the UK it is important in providing food and shelter for a variety of species. Over 300 insect species are supported by hawthorn trees, including the caterpillars of hawthorn, light emerald and fruitlet mining tortrix moths. Pollinating insects visit the flowers as a source of nectar, and the haws are eaten by dormice and many birds, including migrating birds such as redwing and thrushes. The dense foliage provides shelter and nest sites for many birds. Hedgerow management is important in maintaining the wildlife value of hawthorn - flowering and fruiting occurs on wood over 2 years old, so hedge cutting has a large impact on the availability of haws. 

A cluster of haws

A light emerald moth (Campaea margaritaria). The caterpillar of this species feeds on hawthorn.

Additional to the ecosystem services this species contributes to, hawthorn has multiple uses for people. The finely grained, hard wood can be used in timber to produce cabinets, tool handles and boat parts. The wood can also be used as a fuel and to produce charcoal, as it burns at a high temperature. Although not as widely eaten as in the past, the young leaves, flower buds and young flowers of hawthorn are edible, and can used raw in salads. The haws are often used in jellies, wines and ketchups. The most prominent use of these trees is as hedgerow shrubs, as if managed to be dense they are stock proof. 


Other tree species that could be confused with Common hawthorn are blackthorn (Prunus spinosa) and Midland hawthorn (Crataegus laevigata). In spring, blackthorn can be distinguished from hawthorn as it flowers earlier in the year, before the leaves appear, and in autumn the blueish sloe berries of blackthorn are clearly different to the red haws of hawthorn. Midland hawthorn leaves are not as deeply lobed as common hawthorn, and Midland flowers earlier than common hawthorn. Midland hawthorn has twin stigmas and seeds in the flowers and fruits, whereas Common hawthorn has single stigmas.

The threats to Crataegus monogyna are limited, although potential issues are aphid attack, gall mites and fire blight disease. 

Common hawthorn is often overlooked in our hedgerows, but actually provides important services for people and wildlife.

More information on Hawthorn can be found here:
https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/british-trees/a-z-of-british-trees/hawthorn/
https://www.sciencedirect.com/science/article/pii/S0167880902001068
https://en.wikipedia.org/wiki/Crataegus_monogyna
https://www.brc.ac.uk/plantatlas/plant/crataegus-monogyna
https://www.iucnredlist.org/species/203426/68083007

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