Don't know if this is a bug or not, but seems unusual. I poisoned a tree in my yard (working on badge) and then accidentally transformed the tree right after. The tree claimed poisoning with the skulls and such swirling about, but the tree changed to something else (bean to bubble), then when the 177 seconds were up, it lived! As the new tree of course. ;)
Not sure if that's supposed to happen, but there ya go!