A sure sign your Birch tree is on the way out.
One way to tell if your birch is dead is if it is laying on the floor and has two beady eyes peering out at you. Presuming this is not the case, another sure fire way to tell if it is dead, dying or dangerous, is the identification of a fungus that grows almost exclusively on Birch trees, Piptoporus betulinus or as it is more commonly known birch polypore, birch bracket, or razor strop.
Whilst doing a few tree removals for a client in Swanley, removing various trees, we had to remove an obviously dead Birch tree. This particular Birch was easy to identify as dead, due to it being void of the tangled mass of twigs known commonly as ‘witches broom’ as well as any sign of leaves or catkins. If there are twigs, but no leaves in summer, this is another obvious sign the tree is dead.
If you look closely at the photo you will notice some bulges coming out from the stem. This is the sign you can look for on living trees to identify the decay of a tree or branch. This is the Birch Bracket fungus Piptoporus betulinus. It is important for tree owners and tree surgeons (who are climbing the tree) to look out for this fungus as it indicates a dangerous decaying tree / branch.
Once the tree was down, I took some close up photos for this article to help you identify the fungus:
A good way to identify wood that has been rotted by this fungus is that the rotting wood will often smell distinctively like green apples. This particular fungus is a necrotrophic parasite on weakened birches. It will cause brown rot and eventually death. It is thought that the birch bracket fungus makes its way into the tree through small wounds, but is suppressed by the trees own immune system until something occurs to damage or weaken the tree. Strong winds, a large fracture in the main trunk, fire or even suppression by other trees can be the culprit.
Prevention or cure?
The tree bracket fungus is a disease that attacks the hardwood. By the time the fruiting bodies appear there is usually a significant amount of interior damage leading to brown rot. The only remedy might be to remove the affected branch. If not the branch will eventually fall, along with the tree. In a woodland area this is merely an inconvenience, close to a property this can be extremely dangerous and removal of the tree by a professional tree surgeon is strongly recommended.
You might be able to remove the brackets, which will stop the dispersal of spores infecting other trees, but generally the fungus attacks old or weak trees.
Cycle of life
It is always sad to lose a tree, especially a beautiful tree like the birch, with its open canopy allowing lots of light to reach the ground, it gives rise to a multitude of mosses and flowering plants which are a common sight adorning a birch wood floor. This in turn gives rise to beetles and a myriad of insects attracting various different species of birds. In fact a whole eco-system is created. Various parts of the tree are also used for medicinal purposes, reportedly useful in the treatment of high blood pressure, high cholesterol, obesity, gout, kidney stones, nephritis, cystitis, digestive disturbances, respiratory diseases, reduce inflammations and infections of the skin such as eczema and psoriasis. These are just a few other reasons to love the birch. It is still worth remembering not to demonise the fungus though, the birch tree itself would not have the mass of twigs known as ‘witches broom’ if it were not for the fungus Taphrina Betulina and it also has a mutualistic relationship with another fungus Amanita muscaria. In the same way a cold is known to be a highly efficient way for a human to get rid of a large amount of dead cells. I believe the birch bracket fungus acts in a similar way in the grand scheme of things, allowing a faster transition from old and weak, to new and young. The fungus itself was found to harbour a large number of species of insects that depend on it for food and as breeding sites. In a large-scale study of over 2600 fruit bodies collected in eastern Canada, 257 species of arthropods, including 172 insects and 59 mites, were found. The fungus is also eaten by the caterpillar of the Fungus moth and is also edible for humans, with a mushroom type odour and bitter taste. The fungus also has medicinal properties, it has anti-inflammatory compounds and antibacterial properties. Compounds found in the fruit body of the fungus particularly polyporenic acid, are poisonous to the parasitic whipworm.
What does this have to do with the 5,000 year old mummy, Ötzi the Iceman?
In 1991 two German tourists were hiking in the Alps when they found the 5,000 year old mummified remains of a person, now known as Ötzi the Iceman. On his person were found implements which included two hide strips, on to each of which a round lump of material had been threaded. The strips were attached to Ötzi’s clothing. Analysis showed that these lumps consisted of the fruiting body of the birch polypore fungus. Why was he in possession of this fungus? Perhaps he was eating them!? On analysis of his stomach it was found that he had consumed food two hours previous to his death and this did not include the fungus. You may have noticed another name for the fungus, razor strop. A traditional use of the fungus was to sharpen razors, but as he had a beard and died before the invention of metals used in razors, we can rule this one out as well. Further analysis of Ötzi then enlightened us to the real reason for his possession of the birch bracket fungus…… he had the parasite whipworm and was using the bracket fungus to treat it.
So maybe the fungus isn’t so bad after all, just another part of the infinitely complex processes of this thing we call life.
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