Salix cinerea/caprea/glauca, which one I am not sure. The S. caprea leaf is far more pointed than the one depicted here, so not that one.
No identification made yet.
No interactions present.
Looks like Salix cinerea subsp cinerea to me, which has narrower leaves than caprea, and is almost always broadest at the 'shoulders' of the leaf. Leaf veins are not deep and 'sage-like' enough for S. aurita. As far as I know, the north American Salix glauca hasn't yet become naturalised in Britain or Europe.
The gall might be Iteomyia capreae, but it would be good to see inside and find a small maggot rather than a very small legless mite.
Missed this somehow :-/
Will see what this summer brings, will be keeping an open foe it...
An iSpot Project- HELP WITH IDS - UK & Ireland Community - PLANTS
I think this is a mite gall, most probably Aculus laevis.
Lat/Lng: 53.2055, -0.5631
OS grid ref: SK960685
Backies woods, Boultham Moor, Lincoln.