So imagine you are farming and everything's peaceful, you go to harvest your crops and one looks slightly different but you ignore it. When you go to harvest this, lets say cabbage, it jumps out of the ground and bites you, turning into a fairly strong monster. Different crops may have a different chance of turning into a Plantaerian, making farming still peaceful, just adding some threat.
Since it was added so recently, it seems like it was taken from Wildstar. Anything you can gather has a 1 in 100 chance of getting up and running away, or turning into a strong monster to fight.
I generally thought of the idea off the chest mimics in "Dark Souls" I have no idea what "Wildstar" is.
http://www.wildstar-online.com It's a MMO with action-based combat set in spaaace. But I have never heard that stuff like this would happen in that game.