You're right, I try to be a good neighbor, so it did stick with me for a while.
And I too have witnessed some of the things Chi Chi mentioned, another reason I didn't like getting accused of being one of "those people."
I was also an avid gardener before our move so I'm very sensitive to all the effort that goes into the smallest bed...
I've most certainly have steered clear of this particular neighbor, and am beginning to suspect you are right about this being her way of interacting, because all signs point to the fact that it is actually her upstairs neighbors who maintain the tree box and have placed the sign there.
Funny enough on Saturday the exact OPPOSITE thing happened to me, where I had a park manager come up behind me and thank me(?)for picking up Scooter's poop... that I really didn't expect.
Now, if anyone tries to scold me for Scooter chasing squirrels, I'm going to laugh in their face, and tell them to get a life. There are real issues in the world.