Legal Question in Real Estate Law in Illinois

Fences and plantings are not considered "permanent" and therefore typically do not result in a claim to "adverse possession". However, you can do a few things: (a) get your neighbor to confirm this is your property in writing -- the consideration could be that he will always take care of the plantings, (b) have a survyor "stake" your property and let your neighbor know, so both of you know where the property line is (according to your surveyor) so there are no issues in the future, or (c) annually notify your neighbor that you give permission for the plantings, so that this is no a "hostile" situation (not in the colloquial but one factor necessary for adverse possession is that the claim be "hostile" in the sense it is not permitted. If you want something more particular you should talk to your neighbor and an attorney can draw up a small agreement in the nature of an easement.