Bearded tooth  (Hericium erinaceum)

Classified as Endangered in the UK.

The bearded tooth fungus is also known as the tree hedgehog fungus. It belongs to the family of tooth fungi, which are rare in Britain, and associated with old trees. This species gets its popular name from its appearance, which does resemble a white hedgehog. It hangs from the trunks or felled ends of trees, usually beech, but occasionally oak, and is cushion-like with long, pendulous spines.

This fungus is edible, though the smell is off-putting. The taste is not particularly distinctive, either. However, this species should not be collected for eating, as it is rare. In fact, it would be illegal to do so, as it is protected under Schedule 8 of the Wildlife and Countryside Act (as amended).

WARNING: many species of fungus are poisonous or contain chemicals that can cause sickness. Never pick and eat any species of fungus that you cannot positively recognise or are unsure about. Some species are deadly poisonous and can cause death within a few hours if swallowed.

This fungus is widespread across continental Europe although it is not common. It is also found in Mexico and North America. In Britain, there were 11 records before 1998, and a survey of the New Forest in that year found 12 specimens. Previous records suggest it has a scattered distribution, with records from Herefordshire, Oxfordshire and Windsor Great Park.

Bearded tooth fungus is associated with old trees, particularly in woods where there has been a continuous history of old trees. It is found on the site of wounds on the tree, often high off the ground.

This fungus produces its fruit body (the visible part of the fungus) from late August to December. They can persist on the tree for up to six weeks, unusually long for a fungus. They have been known to fruit on the same tree annually for many years, and can continue to survive on the tree after it has fallen. Fungi are not plants. They cannot manufacture their own food, and belong to a kingdom all their own. The main part of the fungus is usually invisible, and consists of a mass of fine threads called mycelia, which are underground, or within the body of another organism. The fungus feeds by dissolving the host's tissue, living or dead, and absorbing the chemicals released. The visible part produces spores, the fungal equivalent of seeds.

Not all fungi are destructive to their host. Many forms of heart rot fungi, formerly thought to confirm the death of an old tree, can actually extend its life. A trunk hollowed by these fungi remains as strong as a solid one but weighs much less, and is able to absorb wind shock better than a solid pillar. Other fungi growing on ailing tree limbs can assist in the limb’s amputation, reducing the area of the tree's canopy and the demands on nutrients by the root system. The tree's roots can also grow into the hollowed out core and take advantage of the extra nutrients released into the soil by the action of the fungus. The net effect is a tree which is much less susceptible to wind blow, and which also has a well-fed old age.

The true status of bearded tooth fungus is not known fully, however, old woods with a long history are disappearing in this country, and there has also been a tradition of ‘tidying up’ dead and diseased trees. Furthermore, there is a threat from collectors who remove the fruit bodies for botanical or culinary use, before the spores have been produced.

As well as being protected by law, the bearded tooth fungus is also listed in the UK Biodiversity Action Plans (UK BAPs), and included in English Nature’s Species Recovery Programme (SRP). In order to preserve this attractive species, it is important to maintain its existing populations and ensure that appropriate woodland management is encouraged. One fortunate feature is that this fungus can be cultivated ex-situ . This will allow for a process of inoculation of suitable host trees should it become necessary to do this. In the meantime, mycologists (fungi specialists) are being encouraged to pass all records of this species to a national database. The bearded tooth fungus received a boost by featuring in English Nature’s Species Recovery Programme calendar for the year 2001, a novel pin-up indeed.