It’s odd. Twice, within the space of seven days, have I found a poplar (Populus sp.) cavity to be host to some Rigidoporus ulmarius sporophores. The last time it was slightly more overt, though in this case it really was a case of having to look. This poplar is by quite a busy residential junction, and given its poor condition around the base (from Sesia apiformis exit holes, general mechanical damage of roots and the butt, and the fungal decay – perhaps all are associated), one would perhaps reasonably expect for there to be a form of risk management involved with this tree’s future.
Below are some photos that I think give a good indication of the situation, and why the fungal decay was not necessarily entirely discernible from the outside.