Cauliflower Fungus (Sparassis crispa)

Whoever heard of a cauliflower fungus? Well, there is one and it is a major cause of windthrow of pines. The name comes from the convoluted shape of the fruitbody - but maybe 'coral fungus' would be a better description.

This pathogen enters tree roots via wounds and grows up the root system towards the trunk. It can decay the base or lower trunk but the main damage occurs in the root system, where it is very difficult to quantify. Because of this it is a dangerous fungus and difficult to tolerate on trees near to people or structures.

On a recent case I checked for decay at the base on the assumption that the fungus would only affect this wood if it was well established in the root system, and therefore, likely to be affecting stability. I thought if there was no basal damage we could then use an air spade to expose the roots around the fruitbody with the hope that we could clearly distinguish between weakened and unaffected roots.
We found decay beginning in the base and the tree is being carefully monitored until it can be removed safely.
The fungus is usually around 30cm in diameter and found close to the base of the tree. It is annual and grows through the summer. It is edible but usually nibbled by squirrels rather than humans. In autumn the cold weather causes it to become slimy and dissolve.

New massive fungus found in China

I've just seen this article on the BBC website; http://www.bbc.co.uk/nature/14294283 .
The fungus Fomitiporia ellipsoidea is, apparently the largest fungus yet found anywhere in the world.  It is growing on the underside of a fallen tree trunk and weighs half a tonne!
These types of wood-eating fungi are usually found on dead wood rather than on live wood.  They break down the dead wood into its constituent chemical parts.  They don't usually pose a safety risk to the tree or to people and property as long as the tree is alive and there is enough new wood to keep it healthy and stable.  Obviously, if the whole tree is dead this could cause safety problems.
The main problems for safety of people and property is when an aggressive fungus attacks the living tissues in a tree.  If this happens the stability of the tree can quite easily be affected.

BBC Nature - Giant fungus discovered in China

BBC Nature - Giant fungus discovered in China

Beware of false charcoal (Ustulina deusta)

One of scariest fungus diseases is Ustulina deusta (ust-you-liner doy-ster). It rots the wood without there being any external, compensatory growth by the tree, the fruitbody is small, black or grey and not easily spotted and, to cap it all, it was renamed a few years ago and its new name is even harder to say!  Try getting your jaw round Kretzschmaria deusta.

Ustulina deusta fruitbody on beech

Clear reaction zones in lime stump

This disease weakens the wood of the tree, principally near the base, and leaves it very brittle and liable to fracture.  I’ve known trees to collapse with little wind and no warning.  Once felled you can see that the affected wood has become very hard and inflexible, the fracture plane of wood is described in the books as being like a ceramic surface.  In the wood of the broken tree you can see many sharp, dark lines zigzagging across its cross section.  These show where different fungus individuals have bumped into each other and formed a boundary.

The perennial fruitbody is dark grey to black and grows like a scab on the bark or exposed wood.  The scab is knobbly and it looks a bit like charcoal.  But it doesn’t smear your fingers with carbon when you crush it.  If the infection is at an advanced stage there may be quite an area around the base of a tree covered in the fruitbodies.

I’ve often seen Ustulina growing on beech alongside Ganoderma brackets, the two fungi working in concert to strip the wood of any nutrients they need.

In Spring the new fungus growth appears grey rather than black.  This is an asexual stage of growth.

Asexual growth growing on normal growth in early spring

Ustulina attacks many broadleaved species but I’ve seen it mostly on limes and beech.  Wherever it is found it is a potential hazard and, if there are people or property close by the tree should be checked out thoroughly as quickly as possible.

Chicken of the woods

Don’t count your Chickens of the woods before they grow, and don’t ignore them when they don’t show.

The large, fresh yellow, annual fruitbodies of Laetiporus sulphureus are known as ‘Chicken of the woods’. They grow from May to autumn and are found on many broadleaved trees, but especially oak, in UK. I suppose the name arises from people wandering through woods and spotting a yellow lump in a branch fork, seemingly with wings. ‘Look! There’s a chicken’ they wound presumably cry.

You can often find them growing out of old wounds on the trunk or main branches of a tree, but they can grow near the ground too. I’ve seen a bright yellow one on a plum stump and an old, white one at the base of a wild cherry. The overlapping, fleshy fans can reach up to around 1m across but they do get eaten so older ones may look a bit dog-eared.

The bright yellow colour fades over the growing season and the fungus looks white and chalky when it is old. The disease can be in a tree for decades and the fruitbodies don’t appear every year, which is typical of the unhelpfulness of fungi.

The fungus causes a brown rot in the wood of a tree by eating the pale cellulose and leaving the darker lignin. Eventually the wood degenerates into brown or reddish cubes and often you can see a white mycelium, like a skin connecting them.

The disease can be a health and safety issue if the tree is close to lots of people as it is difficult for the tree to adapt to the loss of cellulose, which provides the flexibility of the wood. Trunk or branch can, then, become brittle and weak. So, if you see this fungus on a tree but then it doesn’t appear the next year that doesn’t mean it has gone away. It’s still there, munching on the cellulose – you’ll see it again sometime.

This can be a spectacular fungus and, when young, it is supposed to be edible, though I haven’t tried it myself.

Young fruitbody on oak

Mature fungus and brown rot of oak

Old fruitbody on robinia

Phaeolus schweinitzii

Phaeolus schweinitzii is a serious fungal disease of most conifer trees. It usually enters the tree via root tips and weakens the roots as it utilises the cellulose in the wood for food. It can reach right up to the base of the tree and even into the lower trunk. I have found Pheaolus high up in trees, but only rarely.

Young, yellow fruitbody





Mature brackets near base of Douglas fir.



The fungal fruitbody starts off as a formless yellow lump, growing out of the ground near a tree or else from its base or maybe from a wound on the stem. The bright, sulphur yellow colour is quite distinctive and shows that the bracket is actively expanding. These are found from May to August but older ones can last longer where they are protected from the weather. Once fully grown the yellow colour gives way to a rich brown and the top of the bracket is stiffly felty. Old fruitbodies are dull, grey or black and look very uninviting. The brackets can get up to nearly 1m in diameter but I usually see them less than half this size.

The disease is very serious and when the brackets appear it usually means that the decay is quite extensive. Trees with Phaeolus are liable to windthrow (because the roots lose their strength) or breakage on the lower trunk (because the centre of the base is so decayed that there is not enough healthy wood to deal with the stresses of the wind). It is very difficult to quantify the loss of root strength and so the appearance of the fruitbodies is a major safety issue.

Old brackets gradually disintegrate.

I'm back with news of a tree book

I've not blogged for a while. It's a good job nobody's been holding their breath waiting.
My news is that I have written a book called Urban Trees, a practical management guide. It's about trees and the development of urban areas from a UK perspective.  The publisher is Crowood Press and I expect it to be published in the autumn, 2011.

Beefsteak fungus

Beefsteak fungus (Fistulina hepatica) is often found on oak, although I've found it on sweet chestnut in the past. At its early stages is doesn't appear to affect the strength of the wood, and has been known as the cause of 'brown oak' timber but as the disease progresses a brown rot develops due to the fungus preferentially eating the cellulose in the wood and leaving the darker coloured lignin intact.
It is usually associated with the base of trees. The highest I recall seeing it on a tree is around 1.5m above ground level.
The fungus is either red or pinky-brown and is fleshy to the touch. When I touch the fungus the feeling of flabby, fleshy weight in my hand suggests to me a cow's tongue rather than a beefsteak.If you cut it the inside flesh is pale pink with darker pink flecks. The fruitbody usually has a short, thick stem which sticks out of a wound or damaged part of a tree. It can be quite large, sometimes as wide as 40cm or so.
My most authoritative fungus book (Encyclopedia of Fungi in Britain & Europe, M Jordan) says beefsteak fungus is edible and tastes slightly acidic. I've never been tempted to try it.