One species each day (from my backyard)

This species is invisible in this picture, but these galls are characteristic for the mite Eriophyes hoheriae that produces them, and only on this genus of trees.  Again I had no other pictures for this day, so I had to identify this one too, but it was an easy one. I'll leave the tree species for when it flowers again, which could be a while, because it was still flowering when I started my 'One species each day' exercise.