Dr Terry Mabbett ventures into the woodlands of Hampstead Heath to observe the inoculation of beech trees with fungi as part of a scientific research project.

CONSERVATION is a key watchword in UK forestry. High-profile mammalian species like polecat, pine martin, European beaver and red squirrel may get the publicity, but endangerment affects living things across the animal, plant and microbial kingdoms.

The latter includes so-called dead-wood fungi, a huge range of basidiomycete saprotrophs inside dead and declining trees, digesting and decomposing wood and recycling the nutrients. And they are essentially unseen until fruit bodies as mushrooms, toadstools or brackets burst forth around or on the trees.

Within Europe, the UK has more than its fair share of unmanaged woodland with a wealth of ancient and veteran trees, so you might think wood-digesting and -decomposing microbes are essentially safe. However, many of these basidiomycete fungi with a range of parasitic and saprotrophic feeding tendencies are increasingly rare, prompting scientific research around the reintroduction and consolidation of these vital fungal colonisers of trees and woodland.


On a sunny September day I accompanied Ian Chedgy, arb consultant and hands-on arborist, to Hampstead Heath in north London where he was about to start research for a master’s degree. Ian had recently enrolled at Cardiff University to research decomposition fungi associated with common beech (Fagus sylvatica). Research is supervised by Professor Lynne Boddy, decomposition ecologist/fungal ecologist in the School of Biosciences at Cardiff University.

Ian was armed with inoculum of two dead-wood fungi which should be commonly associated with Fagus sylvatica, but are increasingly rare, despite the country’s beech-rich woodland, concentrated in southern England, being generally populated with old, declining trees and habitats for these microbes.

Fungi in the spotlight for the day were Hericium coralloides (coral tooth fungus) and Hericium erinaceus (hedgehog or lion’s mane mushroom), with native common beech in the 70- to 100-year age range as target trees for inoculation. Given the sell-by date for standard (maiden) woodland beech is 200 to 250 years, and the subject is dead-wood fungi, I asked Ian why he was not inoculating older beech trees visibly in decline or dead but still standing.

“The reason is that older trees may already have heart-rot communities established which could affect the ability of the Hericium fungi to invade and colonise beech heartwood,” said Ian.

These Hericium fungi are classic decomposers of beech heartwood and the autoclaved substrates on which Ian and his colleagues at Cardiff University had cultured mycelium and spores were of beechwood.

Forestry Journal: Jack O’Brien drills a hole ready for inoculation with the Hericium fungus as Ian Chedgy looks on.Jack O’Brien drills a hole ready for inoculation with the Hericium fungus as Ian Chedgy looks on.


Ian had clearly set himself a tall order, having to find and identify 15 appropriately aged beech trees across Hampstead Heath and carry out two inoculations on each tree with the drilling of holes deep into the trunk. These holes required diameters sufficiently large to accommodate the fungal-colonised substrates as standard-shape and -size cylinders of colonised beechwood or beech sawdust, as the inoculation delivery systems used on that day.

We had arranged to meet with David Humphries, trees management officer, City of London Corporation, who subsequently saved the day by bringing along his team of arborists to help. So, together with Alasdair Nicoll (arborist team leader), Jack O’Brien (climbing arborist) and Tom Radusin (apprentice arborist) we now had four guys with 45 years of work and experience on the trees and in the woodlands across Hampstead Heath.

These guys were no tree choppers and loppers, but thinking arborists with deep interest, knowledge and commitment to woodland ecology and conservation in the urban environment. Clearly there is no way such a large, varied and ecologically sensitive area like Hampstead Heath could be managed without this kind of commitment.

Ian is no shrinking violet when it comes to hard physical work but was clearly grateful for the help. David Humphries and his colleagues were able to pinpoint pockets of suitable beech trees across Hampstead Heath, lead Ian straight to them and carry out a large part of the work involved.

First port of call was the area around Leg of Mutton Pond on West Heath where David had previously identified a closely knit group of three beech trees estimated at 70 to 80 years of age. Alasdair Nicoll tagged each tree by lightly nailing a numbered metal disc, and adding how he hoped they would stay in place. I assumed he was referring to potential removal by curious members of the public but Alasdair said grey squirrels and parakeets are the most likely culprits when tree identification discs go astray.

Tom Radusin and Jack O’Brien drilled the holes using a battery-powered RDS drill fitted with a spade attachment, cleaning out the residual, fresh and white beech sawdust with their fingers along the way. This caused Tom and Jack to comment on how the drilling was generating a lot of heat at the interface of the tree’s heartwood and the metal spade attachment. I asked Ian and David if they thought this could impact on inoculation and colonisation by the fungi.

“Heat could cauterise the wound and make it harder for the fungal mycelium to penetrate, although by the same token the heat-modified wood may be easier for the fungus to decompose,” they said.

I asked the Heath team whether successful inoculations and colonisations would be firsts for these Hericium fungi.

“Local mycologist Andy Overall, who has monitored fungi across Hampstead Heath for the last 20 years, has recorded H. erinaceus, which is a BAP (Biodiversity Action Plan) species protected by law, but has not yet found the even rarer H. coralloides,” said Tom.

David said: “Hericium cirrhatum has been identified on beech and birch. Hericium erinaceus is on the Red Data List of Threated British Fungi and protected under the Wildlife & Countryside Act 1981.”

Our next stop was Sandy Heath. The name reflects an earlier character of the site before huge quantities of clay, sand and gravel were excavated in the 1860s for making bricks and laying railways – especially the Midland Railway Company’s line into London St Pancras less than two miles away. The area is well wooded but the trees were, with few exceptions, no more than 150 years old. The two most notable exceptions were a pair of veteran English oaks perched on a hillock and with exposed collars and roots as testimony to that time 150 years ago when the surface layers were stripped off right across the site.

Walking around Hampstead Heath you can be forgiven for thinking you are within a huge expanse of ancient woodland but this is not the case, said David.

“There are pockets of authentic ancient woodland but most of what you see has generated over the last 150 years. Prior to that, Hampstead Heath was a huge, sprawling grassland heath providing grazing resources for the inhabitants of surrounding villages including Hampstead and Highgate. Indeed, the Hampstead Heath landscapes painted by the artist John Constable during the early part of the 19th century clearly show a working heathland setting with just a smattering of trees including broadleaves and pines,” he said.

Whenever the subject of John Constable’s paintings arises, his native Suffolk always springs to mind, but just as many if not more of his paintings feature Hampstead Heath. Indeed, every summer between 1819 and 1826 (except 1824) Constable took a house in Hampstead with his family. In 1827 he settled there permanently and, as he told his friend John Fisher, the arrangement allowed him to unite a town and country life. During Constable’s lifetime, Hampstead Heath was a working landscape with sand-diggers and grazing cattle, which comes across on his canvases. Hampstead Heath’s long tradition of sheep grazing saw a renaissance this year when grazing sheep were reintroduced for the first time since the 1950s.

Forestry Journal: The Hampstead Heath tree team. From left to right: Jack O’Brien, Alasdair Nicoll, David Humphries, Tom Radusin.The Hampstead Heath tree team. From left to right: Jack O’Brien, Alasdair Nicoll, David Humphries, Tom Radusin.


However, it was now time to find out more about these four members of the Hampstead Heath tree team who had made the first day’s work of this project possible. Trees management officer David Humphries has 35 years’ experience on Hampstead Heath, having started his career in an apprenticeship with the GLC (Greater London Council), when Ken Livingstone was its leader and Margaret Thatcher was Prime Minister. David studied at Capel Manor (Enfield, North London) and Merrist Wood (Surrey) Colleges, achieving qualifications in arboriculture up to and including Level 4. “I have seen many changes,” he said, adding how the job fulfils his deep interest and commitment to ecology and conservation in the urban setting.

Forestry Journal: Fruit body of Hericium erinaceus on Hampstead Heath.Fruit body of Hericium erinaceus on Hampstead Heath.

“My title is ‘trees management officer’, but with over nine million visitors to the Heath every year, perhaps ‘people management officer’ should be my title.”

This crucially important aspect of the work came across strongly from Alasdair Nicoll who showed us how they were making use of cut tree material to construct dead hedges.

“Though clearly providing cover for wildlife, the main reason for dead hedging is to deter the public from entering sensitive areas. Under the Hampstead Heath Act we can’t put up fences so this is the ideal environmentally friendly alternative,” said Alasdair.

Forestry Journal: The beechwood inoculation delivery system colonised by Hericium coralloides.The beechwood inoculation delivery system colonised by Hericium coralloides.

The material used for this particular dead hedge had come from the haloing exercise performed around the two veteran oaks on the hillock nearby. Alasdair, who is arborist team leader, has been on Hampstead Heath for five years and, prior to that, was working as an arborist in the West Country. Asked what he really liked about the work, Alasdair said: “Conservation-related urban tree management and the creation and maintenance of open spaces for people. Many schools from neighbouring London boroughs come onto Hampstead Heath to take advantage of the wealth of ecology and biodiversity we have to offer, including a much wider range of trees than would be found in rural settings.”

Jack O’Brien is a climbing arborist and has four years with the City of London Corporation at Hampstead Heath. Jack studied at Capel Manor College, starting with countryside management and progressing through arboriculture education and training up to and including Level 3.

“The wide variety of tree work is one of the things that make this job attractive,” said Jack.

Tom Radusin has been an apprentice arborist with the City of London Corporation at Hampstead Heath for the last 18 months. He has enrolled on the Arborist 180 course (Level 2 arboriculture) at Capel Manor College and is planning to progress onto Level 3. Tom is clearly thriving in arboriculture, having previously been office bound, which he says just does not compare.

Forestry Journal: David Humphries drives home a beechwood cylinder colonised by the fungus.David Humphries drives home a beechwood cylinder colonised by the fungus.

With 15 trees and over 30 inoculations completed, there was still some inoculum remaining, so we made for The Beeches at South Meadow which, as the name suggests, is a large grove of absolutely amazing beech trees. The team identified a tree which had lost a massive lower limb, cleaving off a substantial slice of the bole to leave a gaping wound. Miraculously, the tree had not only survived, but, apart from a huge but subsequently self-sealed and healed wound, was in good active-growth condition. Ian suggested we inoculate the fallen limb (now dead as a doornail), working on the basis that colonisation of this truly dead wood would be that much quicker.

Ian’s efforts at Hampstead Heath are essentially selfless, because any concrete results are unlikely to materialise within the relatively short time period of a master’s degree. However, with this time lapse in mind, inoculations have been carried out in previous years around the country. Ian hopes to gain data from beech trees in North Wales inoculated with these same Hericium fungi 10 years ago. Hampstead Heath is not the only prime site benefitting from this project. Similar inoculations have been set up at Windsor Great Park and Savernake Forest by postgraduates Matt Wainhouse and Emma Gilmartin.

Forestry Journal: Tom Radusin packs fungal colonised beech sawdust tightly into the hole.Tom Radusin packs fungal colonised beech sawdust tightly into the hole.


Heading back into central London, it was time to reflect over a flat white coffee and a beechwood-cured bacon sandwich, and to look back 45 years to the biggest rubber plantation in West Africa. Nine million Hevea brasiliensis trees were at threat from a clutch of basidiomycete fungi – Ganoderma pseudoferreum, Rigidioporus lignosus, Phellinus noxius and the worldwide favourite Armillaria mellea – knocking down young, pre-tapping rubber trees like nine-pins. Trees in the worst-affected stands were already of a size and age which meant replanting was not practically possible. As such, every rubber tree lost to fungal infection and disease represented 30 years of future rubber latex production, which at 10 kg annually is a lot of latex.

Understandably, we did everything possible to exclude these basidiomycete fungi and protect the trees, but today I had seen the inoculation of healthy beech trees with basidiomycete fungi. I can’t begin to imagine what my American boss, a good ol’ boy from south of the Mason–Dixon Line, would have said. Back then his policy was: “If it’s green, spray it. If it moves, shoot it”.

Forestry Journal: Alasdair Nicoll (pictured) says dead hedging is the ideal environmentally friendly alternative to fencing for keeping the public away from sensitive areas.Alasdair Nicoll (pictured) says dead hedging is the ideal environmentally friendly alternative to fencing for keeping the public away from sensitive areas.

Common beech has long since lost any status as a commercial, hardwood timber tree, with the last beech bodgers vacating the Chiltern Hills’ beech woods many decades ago. Landowners now trying to sell beech for timber are offered prices considerably less in real terms than they were receiving 20 years ago. Today’s beech harvest, such as it is, invariably goes for firewood. Such a situation would clearly depress any new beech planting if it was not already at rock bottom due to grey squirrel damage.

Nevertheless, beech is an increasingly important native tree component of southern England’s semi-natural broadleaf woodlands, with increasing numbers of trees assuming veteran and ancient status as time goes by. Provided beech trees can avoid the dreaded and all-too-common windblow, mature beech grows old gracefully, with decomposition fungi making the process all the more useful, attractive and interesting from the soil fertility, biodiversity, conservation and sheer enjoyment points of view.

Notes on the fungi:

Hericium coralloides

This highly distinctive fungus bears large (25 cm wide) fruiting bodies which are white and branched to resemble coral. Each branchlet bears downward-pointing spines 5–10 mm in length. Typically found on fallen trunks and large logs, Hericium coralloides occurs most frequently on common beech and less so on common ash and elm.

Hericium erinaceus

Produces white football-sized fruiting bodies comprising clusters of extended (10–40 mm), downward-pointing and icicle-like spines. Hericium erinaceus is frequently found fruiting high up in the canopy on exposed, central dead wood of old standing beech and oak trees.