You can nab this trophy a few different times. The area first comes available when you're walking through the "spooky forest" paths and can interact with some of the Orange bushes. If Graham interacts and says "Here Kitty Kitty .... " you're in the right area.
All the way on the Northern part of this screen is the path to an old Well with the Snipiferous Thornweeds. Simply walk through them to meet a grim fate, then wait it out in the Continue screen for Old Graham to make a pun about the situation. Trophy unlocked!
Note: you can return to this area when questing for the Eye, but you'll want to complete popping this trophy before you buy the weapon from the Blacksmith that you'll then use to chop the Weeds down.