This isa mystery. It is a distorted flower bud on a magnolia. It appears to be a wasp gall but hosting numerous larvae, rather than one. The white spots are odd though.
This is a fully mature specimen tree grown in a huge pot, so I would guess sourced wholesale from Italy.
Galls are normally quite specific but I can't find any reference to a specific wasp.
Magnolia is not a UK native so my presumption is that this is an invasive. I intend to remove the galls and destroy them, as a precaution.
Has anyone seen these before?