Iros

From Tardis Wiki, the free Doctor Who reference

The planet Iros was home to one of the most beautiful "man-made" gardens in the universe. Its creators ensured the garden was maintained by an army of robot guardians (resembling the garden gnomes found on Earth), that preserved and maintained the garden beyond the lives of their creators.

The top of the range guardian robots however were unable to fix faulty systems like the sprinklers nor were they able to distinguish between "pests" and "visitors". (COMIC: Gnome Guard)