If you're sure it's your hedge AND you own the property then I suggest a quiet word. He may not have realised that he was doing wrong (or he may have but that's another thing). Culture differences can be a funny thing.
You need to keep civil with your neighbours firstly cos it makes a more pleasant living environment and secondly, cos you have to declare any neighbour issues when you come to sell.
If it's not your hedge OR, you're renting yourself then it's up to you what you do, if anything.
Put a 6ft fence up.