no it wont let them know - you will just dissapear from their friends list. it will not appear in the news feed as is stated in facebook help - which is worth a read - if you have the time. its the same as ignoring a friend request or blocking someone.
hope this helps. dont panic pumpkinhead - facebook have thought about potentially offending people versus privacy xx
try forking some blood fish and bone meal powder into the soil surrounding the roots - same happened with my privet hedge and this worked a treat. lightly water the stuff in. good luck with it.