Collect hawthorn samples for National Hedgerow Week 2026

How you can help this iconic hedgerow species...

Common hawthorn field hedge, Warwickshire, April 2026. Credit: Joana G. Vicente

Join The Tree Council and Forest Research for a special free online talk discussing this live research project, on Thursday May 7 from 1-2pm. Book your spot here

Hawthorn is one of the most familiar plants in Britain’s countryside. Found running alongside lanes, fields and footpaths, it has long formed the backbone of traditional hedgerows and rural field boundaries. Closely linked with British folklore and rural heritage, hawthorn is a defining feature of the landscape and a species many of us pass every day without a second thought.

Hawthorn makes up an estimated 70 per cent of UK hedgerows and plays a crucial role in supporting biodiversity, storing carbon, preventing soil erosion and connecting habitats. Despite its importance, relatively little is known about the resilience of hawthorn. A new national research initiative is now inviting volunteers to help change that.

Flowers of common hawthorn (Crataegus monogyna), Warwickshire, 2026.; Credit: Joana G. Vicente

Helping build a clearer picture of hawthorn health

The project, a collaboration between Forest Research, The Tree Council, Fera and the International Plant Sentinel Network, aims to assess the resilience of hawthorn across the UK and understand how any vulnerabilities could affect the surrounding treescape.

By collecting hawthorn samples from across the country, volunteers can help researchers build a clearer national picture of hawthorn health. This information is essential for understanding how hedgerows may respond to future challenges and for supporting their long‑term protection.

The project focuses on two key diseases affecting hawthorn: fireblight caused by Erwinia amylovora and rusts caused by Gymnosporangium species.

Common hawthorn in flower as part of a mixed untrimmed hedge, Warwickshire, April 2026. Credit: Joana G. Vicente

The many benefits of hawthorn

Hawthorn plays a vital role in supporting wildlife throughout the year. Its dense, thorny branches provide safe nesting sites for many bird species, offering shelter and protection. In spring, hawthorn flowers provide nectar and pollen for bees and other pollinators, while in autumn the bright red berries, known as haws, are an important food source for birds and small mammals.

Hawthorn is also highly valued in land management. Its tough, thorny growth makes it ideal for hedge laying, creating dense, stock‑proof barriers that are effective for containing livestock. Hawthorn hedges help prevent soil erosion and act as natural windbreaks, supporting both farming and the wider environment.

Common hawthorn (Crataegus monogyna) in November. Credit: Adrian Searle[CG1]

Identifying hawthorn

Hawthorn typically grows as a dense, thorny shrub, although it can also develop into a small tree reaching up to 15 metres tall with a single stem. Its branches are often armed with sharp, woody thorns, and its leaves are around 6 cm long.

In late spring, usually around May, hawthorn produces abundant clusters of flowers with five petals. These are typically white, though they can sometimes appear pale pink. By autumn, the flowers mature into bright red berries.

The two main types of hawthorn commonly found in the UK are:

· Common hawthorn has deeply lobed, toothed leaves. Its flowers have a single stigma, and its berries contain a single seed.

· Midland hawthorn has shallower lobes on the leaves. Its flowers have two stigmas, and its berries usually contain two seeds.

Haws (berries) of common hawthorn, Warwickshire, August 2025. Credit: Joana G. Vicente

Fireblight

Fireblight is a bacterial disease caused by Erwinia amylovora. It is found in Western Europe, including the UK, North America, most countries around the Mediterranean Sea and New Zealand. The disease can spread through pruning tools, as well as via rain, wind, insects and birds.

Symptoms of fireblight of hawthorn caused by Erwinia amylovora in the Emilia-Romagna region, Italy. Credit: Chiara Delvago.

The disease can affect a large number of species of the Rosaceae family including pear and apple, and hawthorn is considered a reservoir for the fireblight pathogen.

Symptoms can be observed from April to September and include a brown to black, necrotic or burned appearance of leaves, flowers and fruits. Affected plant parts often wilt but remain attached. Shoot tips may bend into a hooked ‘shepherd’s crook’ shape. When bark is peeled back, the outer wood and cambium may show a foxy reddish‑brown colour, and exudates may sometimes appear on branches.

Shepherd’s crook symptom on hawthorn caused by Erwinia amylovora in the Emilia-Romagna region, Italy. Credit: Chiara Delvago

Gymnosporangium rusts

Gymnosporangium rusts are fungal diseases affecting hawthorn, caused by species including Gymnosporangium clavariiforme and Gymnosporangium confusum, both present in the UK.

These fungi require two host plants to complete their life cycle. At the start of spring, spores are produced on juniper and these go on to cause infections of hawthorn and other species, including fruit trees. Spores are spread by wind, and disease development depends on environmental conditions and how close suitable host plants are to one another.

Symptoms of fireblight of hawthorn caused by Erwinia amylovora in the Emilia-Romagna region, Italy. Credit: Chiara Delvago.

Symptoms usually appear from early Spring on leaves and stems and can continue through summer, when fruit may also be affected.

Signs to look for include bright orange‑yellow or cream spots on the upper surface of leaves, sometimes with brown or black dots at the centre. Brown/red, swollen areas may appear on leaves, stems and shoots, resembling insect galls but with small, soft, cream to pale brown, hair‑like structures growing from swollen areas. These release fine, powdery, cinnamon-brown spores when touched. Around July, with fruit formation, the hair‑like structures may also develop on infected fruit and masses of spores are produced.

G. clavariiforme infections: pictures of swollen areas at the mid-vein (top image) and base (bottom image) of the leaf with the hair-like structures. Credit: Debbie Frederickson-Matika

How volunteers can help

By taking part, volunteers can play an active role in protecting one of the most important plants in our hedgerow landscapes. Anyone with an interest in trees, nature or the environment is welcome to get involved, whether you are an experienced observer or completely new to tree health.

Next steps:

· Look out for hawthorn hedgerows or single trees and inspect for fireblight and rust symptoms. Whether it’s asymptomatic or symptomatic, we’d like to hear from you.

· Fill out a sampling sheet which can be found within the sampling protocol pack and email us pictures.

· If symptomatic, collect and post samples to us.

Two infected fruits showing the cream-brown hair-like structures typical of G. clavariiforme rust infections. Credit: Debbie Frederickson-Matika

Every submission helps build a clearer national picture of hawthorn health, and each sample receives feedback from the project team.

Please remember that volunteers must be over 18 or accompanied by a responsible adult, and permission should be sought before collecting samples on private land.

Download a sampling protocol pack to get started. For more information or if you have any questions, please do not hesitate to contact us at hawthorn.sampling@forestresearch.gov.uk

The project is funded by the Department for Environment, Food and Rural Affairs (Defra).

National Hedgerow Week runs from May 4 -10, for more information and to access resources, please visit www.nationalhedgerowweek.org.uk. And don’t forget join us for a free online talk, Helping the mighty hawthorn! on Thursday May 7 from 1-2pm.

MORE: Nigel Adams on hedgerow species and planting considerations

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