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Signs to look for

When should I call a tree surgeon?

Most trees give warning before they fail, and most of what worries people is harmless. This page shows the fungi, rot, diseases, animal and insect damage we actually see on trees in Cornwall, what each one means, and how quickly it needs looking at. If in doubt, send us a photo: the tree health check is free.

Call now
A safety issue. Keep people and cars away from under the tree and get it looked at straight away.
Get it checked
Not an emergency, but it needs an experienced eye before the next storm season or before it spreads.
Keep an eye on it
Usually harmless or cosmetic. Worth mentioning when we are next there, or if it gets worse.

Warning signs on the tree itself

Most dangerous trees give notice. These are the things to look for from the ground, and the ones that mean the tree should be roped off until someone has looked at it.

A dead standing tree with bare grey branches against a clear blue sky above a garden

A dead or dying tree

Call now
Trees it affects here
Any, but most often ash, larch, sweet chestnut and old conifers in Cornwall.
What it looks like
No leaves in summer, bark falling away in sheets, grey bare branches, fungi around the base, woodpecker holes. A tree that came into leaf late and thin the year before.
Why it matters
Dead wood dries, becomes brittle and drops without wind. A dead tree over a house, road, garden or footpath is one of the commonest emergency calls, and it only gets more dangerous to climb the longer it is left.
What we do
Assess whether it can still be climbed safely. Often it cannot, and a dead tree is dismantled from a platform or with the crane. It is regular winter work.
A windblown eucalyptus lying across a lawn with its root plate torn up beside the house

Soil lifting or cracking around the base

Call now
Trees it affects here
Shallow rooted trees on wet or thin ground: eucalyptus, conifers, poplar, willow, beech.
What it looks like
A crack in the lawn on one side of the trunk, a raised hump of soil, roots showing where they did not before, or the whole tree leaning a little more than it did last month. Often noticed after a gale.
Why it matters
The root plate is starting to rotate. The tree is failing in slow motion and the next strong wind can finish it. This is the failure that flattens cars and conservatories.
What we do
Rope the area off, then either fell it or, on a valued tree with limited movement, reduce the sail and monitor it. Nearly always removal.
A split fork or a hanging broken branch in a crown

Photo: Smartse, CC BY-SA 3.0, via Wikimedia Commons

Cracks, splits and hanging branches

Call now
Trees it affects here
Any. Forks with included bark on beech, ash, willow and poplar split most often.
What it looks like
A vertical crack down the trunk or a main limb, a fork that has started to open, a branch hanging in the crown after wind, or bark torn where a limb has begun to tear out.
Why it matters
A split limb is already partly detached. It can hold for months or go in the next breeze, and there is no way to tell from the ground which.
What we do
Remove the hanger or the split limb, and look at what is left. Sometimes a cable brace saves a fork that has only started to open.
A leaning conifer above a garden fence with the work van parked in the drive on removal day

A lean that was not there before

Call now
Trees it affects here
Any. Tall conifers and leylandii screens on shallow ground, and trees on Cornish hedge banks.
What it looks like
A tree that has always been upright now leaning, or an old lean that has got worse. Fresh soil disturbance on the side away from the lean.
Why it matters
Trees that have always leaned have built their wood to cope. A new lean means the roots or the stem have failed on one side.
What we do
Look at the root side first. Removal in most cases; sometimes a heavy reduction to take the weight off while the tree is monitored.
A large limb dead and bare while the rest of the crown is in leaf

Photo: Robin Webster, CC BY-SA 2.0, via Wikimedia Commons

Dead wood in a living crown

Get it checked
Trees it affects here
Oak, beech, ash, sweet chestnut, old apple trees.
What it looks like
Bare branches among leafy ones, bark peeling off individual limbs, twiggy dead ends, small branches on the lawn after every breeze.
Why it matters
Normal on a big old tree, and part of why oaks are so good for wildlife, but a dead limb over a path, drive or play area is a hazard. A whole side dying back points to root problems or disease.
What we do
Dead wooding: take out the dead branches over the places people go, leave what is safe to leave for the wildlife, and check the crown for the cause if the die-back is spreading.
A cavity in an old trunk with a woodpecker hole

Photo: Basile Morin, CC BY-SA 4.0, via Wikimedia Commons

Hollows, cavities and woodpecker holes

Get it checked
Trees it affects here
Old oak, beech, ash, sweet chestnut, willow, horse chestnut.
What it looks like
An opening in the trunk or at a branch stub, dark stain or rot running out of it, a woodpecker's neat round hole, or a hollow sound when knocked.
Why it matters
A hollow tree is not automatically dangerous: a tube is strong, and many ancient trees are hollow. What matters is how much sound wood is left around the hollow and what is above it. Woodpeckers only nest in wood that is already soft.
What we do
Sound the stem, probe the cavity and look at the fungi involved. Often a reduction to keep a hollow veteran safe rather than removal. Cavities are also bat roosts, so we check before any work.

Fungi and rot

A fungus you can see on the outside means the fungus has been inside for years. Which one it is decides how worried to be: some hollow a tree slowly over decades, some make it unsafe within a couple of seasons. Cornwall's mild wet climate suits all of them.

Honey fungus toadstools clustered at the base of a tree in autumn

Photo: Wolfgang Moroder, CC BY-SA 3.0, via Wikimedia Commons

Honey fungus

Armillaria species

Get it checked
Trees it affects here
Almost anything: conifers, privet and laurel hedges, apple, birch, willow, rhododendron. Common in old Cornish gardens.
What it looks like
Clumps of honey-coloured toadstools at the base in autumn, black bootlace strands under the bark and in the soil, a white fungal sheet that smells of mushrooms when the bark is lifted. Trees die back suddenly, often one after another along a hedge.
Why it matters
It kills the roots and the base of the tree, spreads underground to neighbours through those bootlaces, and there is no chemical control. A honey fungus tree becomes unstable at the base.
What we do
Confirm it, remove the dead and dying trees with as much root and stump as we can get out, and advise on what to replant that resists it.
A hard brown Ganoderma bracket at the base of a beech trunk

Photo: Dr Mary Gillham Archive Project, CC BY 2.0, via Wikimedia Commons

Ganoderma brackets

Ganoderma species

Get it checked
Trees it affects here
Beech, oak, lime, horse chestnut, sycamore. Very common on big garden and park trees.
What it looks like
Hard, shelf-like brackets at the base of the trunk or on the roots, brown on top with a white underside, often dusted with cocoa-coloured spores. They last for years and add a layer each season.
Why it matters
White rot in the base and roots. Some Ganoderma species work slowly and a tree lives with them for decades; Ganoderma resinaceum on oak and beech is faster. Either way the base is weakening.
What we do
Identify the species, check how much of the base is affected, and plan: monitoring, a reduction to shorten the lever, or removal if the rot is extensive.
Giant polypore brackets fanning out at the base of a beech

Photo: Renée Kools, CC BY 4.0, via Wikimedia Commons

Giant polypore

Meripilus giganteus

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Trees it affects here
Beech above all, also oak and lime.
What it looks like
A big rosette of overlapping soft brown fan-shaped brackets on the ground at the base or over the roots, appearing in late summer and autumn, going black and mushy after frost. It can be a metre across.
Why it matters
It rots the roots, not the trunk, so the tree can look perfectly healthy above and still fall over whole. Beech with Meripilus is one of the classic causes of a healthy-looking tree going down in a gale.
What we do
Assess the root plate and how far the decay has spread. On a beech over a house or road the honest answer is usually removal.
Black cinder-like crust of brittle cinder fungus at the base of a beech

Photo: stolbovsky, CC BY 4.0, via Wikimedia Commons

Brittle cinder

Kretzschmaria deusta

Call now
Trees it affects here
Beech, lime, horse chestnut, sycamore, maple.
What it looks like
Easy to miss. A crust at the base of the trunk and on the buttress roots that starts grey-white with a dark edge in spring and turns into black lumpy burnt-looking cinder that flakes off. Looks like old tar or soot.
Why it matters
It causes a soft rot that leaves the wood looking almost normal while it loses its strength, so trees snap at the base with little warning. Arborists treat it as one of the most dangerous fungi on beech.
What we do
Confirm it and check the extent with a probe or resistance drill. Removal is usual where the tree has a target beneath it.
Bright orange chicken of the woods brackets on an oak trunk

Photo: Renée Kools, CC BY 4.0, via Wikimedia Commons

Chicken of the woods

Laetiporus sulphureus

Get it checked
Trees it affects here
Oak, sweet chestnut, yew, willow, cherry.
What it looks like
Bright orange and sulphur-yellow soft brackets, sometimes in big tiers up the trunk, appearing from late spring to autumn. Unmistakable when fresh.
Why it matters
Brown cubical rot in the heartwood of the trunk and limbs. The tree can carry it for a long time, but the affected limb or stem loses strength inside and can snap in wind.
What we do
Work out which part of the tree is affected and reduce or remove that part. Old oaks with it are usually kept and managed.
A rusty shaggy bracket fungus growing from an old wound on an ash trunk

Photo: Stu's Images, CC BY-SA 3.0, via Wikimedia Commons

Shaggy bracket

Inonotus hispidus

Get it checked
Trees it affects here
Ash and apple especially, also walnut and plane.
What it looks like
A single large rusty-brown bracket with a shaggy velvety top, high on the trunk or at an old branch wound, fresh each summer and turning black and falling off in winter, leaving a dark stain.
Why it matters
White rot in the trunk at the point where it grows, which is often where a limb has been cut. Ash already weakened by dieback fails quickly once this is in.
What we do
Reduce the weight above the bracket or remove the affected stem, depending on where it is and what is under it.
Kidney-shaped birch polypore brackets on a silver birch trunk

Photo: rdegeer, CC0, via Wikimedia Commons

Birch polypore and hoof fungus

Fomitopsis betulina, Fomes fomentarius

Keep an eye on it
Trees it affects here
Birch.
What it looks like
Smooth greyish-brown kidney-shaped brackets on birch trunks and dead limbs, or grey hoof-shaped brackets that last for years.
Why it matters
Both mean the wood they are on is dead or dying. Birch is short-lived, and one of these on the main trunk usually means the tree is on its way out within a few years.
What we do
Remove dead limbs over anything that matters, and plan to replace the tree rather than fight for it.
Larch with dead brown tops and dying crowns in a Cornish plantation

Photo: Karel Černý, CC BY-SA 4.0, via Wikimedia Commons

Phytophthora root and stem rot

Phytophthora ramorum and Phytophthora alni

Get it checked
Trees it affects here
Larch, sweet chestnut and rhododendron (P. ramorum), alder along rivers (P. alni). Cornwall has been at the centre of both.
What it looks like
Larch: dead tops and yellowing crowns across a plantation, bleeding cankers on the stem. Alder: thin yellow crowns, tarry black spots on the bark at the base. Sweet chestnut: bleeding patches on the bark and dying limbs.
Why it matters
Phytophthora ramorum is a notifiable quarantine disease: larch with it comes under statutory felling notices from the Forestry Commission, and infected material has to be handled properly. P. alni is not notifiable, but it kills the roots that hold a river bank together. Alders with root rot fail at the base over rivers.
What we do
Report suspected larch or sweet chestnut infection and work to the notice, and remove failing riverside alders safely. Woodland owners with larch should get in touch before the disease is confirmed, not after.

Diseases in Cornish trees

Some are county-wide and cannot be prevented, only managed. Knowing the signs early makes the difference between a planned job and an emergency.

An ash crown with dead top branches and bushy regrowth below, typical of ash dieback

Photo: Bizzarle, CC BY-SA 4.0, via Wikimedia Commons

Ash dieback

Hymenoscyphus fraxineus

Get it checked
Trees it affects here
Ash. Every ash in Cornwall is exposed to it now.
What it looks like
Dead tips and dead patches in the crown, leaves wilting and turning black on the shoot in summer, diamond-shaped dark lesions on young stems where a side shoot joins, a bushy crown of new shoots below the dead top.
Why it matters
Most ash will decline over several years, some very fast. The wood goes brittle from the top down, so a badly affected ash cannot be climbed and drops limbs. Trees over roads and houses need managing before that point.
What we do
Grade the crown, keep the healthy ones and the ones that are showing tolerance, and remove the ones over targets while they can still be climbed rather than craned.
A hedgerow elm with a brown dead section of crown in summer

Photo: Kim Traynor, CC BY-SA 3.0, via Wikimedia Commons

Dutch elm disease

Ophiostoma novo-ulmi

Get it checked
Trees it affects here
Cornish elm in hedgerows, and any elm that has got above about ten metres.
What it looks like
Leaves on one or more branches wilting, yellowing and browning in early summer while the rest is green, then whole limbs dying. Dark streaks in the wood under the bark of a dead twig.
Why it matters
The beetle finds elms once they are big enough and the tree dies within a season or two. Dead elm over a lane is brittle and drops.
What we do
Remove dead and dying elm in winter, when the beetle is not flying, and take the wood off site rather than stacking it.
Dark weeping canker patches on a horse chestnut trunk

Photo: Lamiot, CC BY-SA 3.0, via Wikimedia Commons

Bleeding canker of horse chestnut

Pseudomonas syringae pv. aesculi

Get it checked
Trees it affects here
Horse chestnut.
What it looks like
Dark rusty or black weeping patches on the trunk and main limbs, dried tarry runs down the bark, bark cracking and falling away, thinning crown.
Why it matters
Where the canker rings a limb or the stem, everything above it dies and is then a hazard. Many Cornish horse chestnuts have some canker; the question is how much and where.
What we do
Map the cankers, remove limbs that are girdled, and keep the tree if the trunk is mostly sound.
A cherry branch with silvered leaves beside healthy green ones

Photo: Henk Monster, CC BY 3.0, via Wikimedia Commons

Silver leaf and bacterial canker

Chondrostereum purpureum, Pseudomonas syringae

Keep an eye on it
Trees it affects here
Cherry, plum, ornamental Prunus, apple.
What it looks like
A silvery sheen on the leaves of one branch, then the branch dying back; small purple-brown brackets on dead wood. Bacterial canker shows as sunken oozing patches of gum on the bark and shot-holed leaves.
Why it matters
Both get in through pruning cuts made in autumn and winter, which is why cherries are only pruned in summer. Rarely dangerous, but they take a tree branch by branch.
What we do
Cut out affected wood in summer, back to clean wood, and burn or remove it. Prune Prunus only in June to August.

Animal damage

Squirrels, deer, rabbits and birds all mark trees. Most of it is a nuisance; some of it lets decay in.

Bark stripped from the upper stem of a young beech by grey squirrels

Photo: Rosser, Public domain, via Wikimedia Commons

Grey squirrel bark stripping

Get it checked
Trees it affects here
Beech, sycamore, oak, sweet chestnut and maple between about ten and forty years old, in woods and larger gardens.
What it looks like
Patches of bark stripped from the upper trunk and branches in early summer, pale exposed wood, strips of bark on the ground, then the tops above the damage dying and going brown. On a young plantation, dozens of trees at once.
Why it matters
Where the bark is ringed the top dies, and the wound lets fungi in. It is the main reason so many young beech and sycamore in Cornwall have dead tops or snapped stems. It does not put a mature tree in danger on its own.
What we do
Remove dead tops where they are a hazard, prune to a sound side branch so the tree can carry on, and advise woodland owners on control, which is a separate job.
A young tree with bark frayed off its stem by a deer

Photo: Wasp32, CC BY 4.0, via Wikimedia Commons

Deer and rabbit damage

Keep an eye on it
Trees it affects here
Young planted trees, hedges and coppice regrowth. Roe deer are everywhere in Cornwall now.
What it looks like
Deer: shoots and leaves browsed off up to about a metre, and bark frayed off young stems in spring where bucks rub their antlers. Rabbits: bark gnawed off at ground level, especially in a hard winter, and small trees bitten through.
Why it matters
Rabbits ringing a young tree kill it. Deer browsing stops a tree getting away and turns it into a bush. Neither harms an established tree.
What we do
Guard and fence new planting properly, replace what has been lost, and manage coppice so it gets above browsing height.
A trunk thick with ivy, with the tree's own crown above it

Photo: Richard Sutcliffe, CC BY-SA 2.0, via Wikimedia Commons

Woodpecker holes and heavy ivy

Keep an eye on it
Trees it affects here
Any older tree.
What it looks like
Neat round holes, often in a line, from a woodpecker feeding or nesting; and ivy climbing the trunk into the crown, sometimes thick enough to hide the tree.
Why it matters
Woodpeckers do not damage a healthy tree: they go where the wood is already soft, so their holes are a sign to check for decay. Ivy is good for wildlife and does not strangle a tree, but a heavy crown of ivy adds sail and weight and hides defects, so on a tree with a target below it is worth thinning.
What we do
Investigate what the woodpecker found. Sever or thin ivy on trees over houses and lanes so the tree can be seen and the wind can pass through.

Insects and pests

Very few insects kill a healthy tree on their own in Cornwall. Most are either a sign of something else, or ugly rather than harmful. These are the ones we actually meet.

Cypress aphids on a leylandii shoot

Photo: Pierre Chevillard, CC BY 4.0, via iNaturalist

Cypress aphid on leylandii

Cinara cupressi

Keep an eye on it
Trees it affects here
Leylandii, Lawson cypress and thuja hedges.
What it looks like
Patches of the hedge turning yellow then brown from late spring, often lower down and on one side, sooty mould on the foliage, and greyish-brown aphids on the shoots if you look closely in early summer.
Why it matters
It is the usual reason a conifer hedge goes brown in patches. The brown does not recover: conifers do not regrow from old wood. The hedge survives but keeps the gaps.
What we do
Confirm it is aphid rather than drought or cutting too hard, trim so the gaps are less obvious, and talk honestly about whether the hedge is worth keeping.
Horse chestnut leaves browned and blotched by leaf miner in late summer

Photo: Stephen James McWilliam, CC BY 4.0, via Wikimedia Commons

Horse chestnut leaf miner

Cameraria ohridella

Keep an eye on it
Trees it affects here
Horse chestnut.
What it looks like
Brown blotches between the veins of the leaves from July, the whole tree looking scorched and autumnal by August, leaves falling early.
Why it matters
It looks dramatic but the moth does not kill the tree. It weakens it a little each year, which matters more on a tree that also has bleeding canker.
What we do
Nothing to the tree itself. Clearing and composting fallen leaves reduces next year's moths. We check the trunk for canker while we are there.
Bark lifted from a dead trunk showing beetle galleries underneath

Photo: SB_Johnny, CC BY-SA 3.0, via Wikimedia Commons

Bark beetles

Scolytus, Ips and others

Get it checked
Trees it affects here
Elm, spruce and pine, and any stressed or dying conifer.
What it looks like
Small round holes in the bark, fine sawdust in the crevices and at the base, bark lifting to show winding galleries carved on the wood underneath. The crown dies from the top.
Why it matters
The beetles mostly attack trees that are already dying, but they spread disease (elm) and can move through a stressed plantation of spruce. A tree full of beetle is not coming back.
What we do
Remove infested trees and take the timber away rather than leaving it stacked on site, where the next generation would hatch.
Beetle exit holes in a dead oak limb

Photo: KaiMartin, CC BY-SA 3.0, via Wikimedia Commons

Beetle holes in dead wood

Longhorn and other wood-boring beetles

Keep an eye on it
Trees it affects here
Dead and decaying wood on any tree, especially oak, beech and willow.
What it looks like
Larger oval or round exit holes in dead limbs and old stumps, sometimes with piles of coarse frass, and occasionally the beetle itself in summer.
Why it matters
They are recycling wood that is already dead and are part of a healthy old tree. They do not attack living wood. The dead limb they are in may be a hazard, but that is the limb, not the beetle.
What we do
Leave standing dead wood where it is safe to. Take it down where it is not.

Questions we get asked

Is a fungus on my tree always bad news?
No, but it always means something. A bracket or toadstool on the outside means the fungus has been in the wood for years. Some, like Ganoderma on an old oak, can be lived with for decades. Others, like giant polypore or brittle cinder on a beech, mean the tree can fail without further warning. The species and where it is on the tree decide it, which is why we ask for a photo.
The tree looks healthy but there are mushrooms at the base. Do I need to worry?
Yes, enough to have it looked at. Root-rotting fungi such as giant polypore and honey fungus attack the part of the tree you cannot see, and the crown can stay green right up until the tree goes over. The free tree health check exists for exactly this.
Squirrels have stripped the bark off my young trees. Will they die?
Where the bark has been stripped all the way round, the part above dies. Where it is a patch, the tree usually seals over it but the wound lets decay in. The dead tops can be pruned back to sound wood and the tree carries on. On a plantation it is worth talking about squirrel control.
What counts as an emergency?
Anything that could fall on a person, a road, a building or a car: a hanging branch, a new lean, soil lifting at the base, a split fork, or a dead tree over any of those. Keep people away from under it and call. Everything else can wait for a visit.
Do you charge to come and look?
No. The tree health check is free, with no obligation. If the tree needs nothing we say so.

Not sure? Send a photo

The tree health check is free

A photo of the fungus, the damage or the whole tree by text or email is usually enough to say whether it is urgent. If it needs a visit, that is free too, anywhere in the TR postcodes.

Call 07867 471048Free tree health check
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