Retain an attorney. Have the attorney serve notice by way of correspondence that serious property damage has been done to your property by the trees which are in his control. Demand that the trees be removed within 30 days and that whatever value that you and the attorney determine is fair, shall be paid within that 30 days, or you will institute litigation.
I know that there are people who will whine that we have a "litigeous" society. However, laws were created at the very most basic level to protect life liberty and property. If the neighbor blows off your correspondence, do not hesitate to take the dispute to court. That's why they built courthouses.
This answer is provided for informational purposes only. Actual legal advice can only be provided in an office consultation by an attorney licensed in your jurisdiction, with experience in the area of law in which your concern lies.