Prunus spinosa, blackthorn or sloe, 55 cm high, about 40 years old, pot by Peter Krebs, collectd in Germany
The fungus is there since 15 years. So often we have a discussion about folks being paranoid about fungus on their trees. Here you see: the overwhelming majority of fungi are harmless. This one lives in old wood and does no harm to the live parts. Or at least did not so in fifteen years.