This is a leaf on a Lime tree

Robert314

It has developed this strange growth can anybody identify and tell me whether it is a problem or is it good?

Thanks

Bob 

madpenguin

Butterfly or moth eggs perhaps?

Dovefromabove

Lime nail galls caused by a mite that lays its eggs in the leaves. 

The big lime trees I knew well as a child were covered with them ... never seemed to do them any harm. The trees are still there and they were huge trees 60 years ago 😊 

DampGardenMan

Brilliant! What an apt name. I must go and check ours, walk past it all day long but have never given the leaves a second glance.