If your neighbor came onto your property to cut down your hedges, that would be trespass. If the hedges are completely on your property, then he probably damaged your property by cutting them. If the hedge was right on the property line, you may have to check your local ordinances to find out more detailed information, as to who is allowed to cut down boundary trees and shrubs. However, in general property owners have the right to cut branches or foliage hanging over their property.
Findlaw.com answered a similar question as follows:
If my neighbor's tree branches hang over my yard, can I trim them?
Yes. By law, you have the right to trim branches and limbs that extend past the property line. However, the law only allows tree trimming and tree cutting up to the property line. You may not go onto the neighbor's property or destroy the tree.