Simple, make it an attribute roll and assign a CR.
People often forget you can do straight attribute rolls. Check out chapter 8,running the game, the last section called Attributes and Action Rolls in Play talks about this.
I would say that the following attributes could each make sense generally but the nature of the world you are playing in and even if plants and animals could have a meaningful conversation boils down to the GM.
Prescience
Alteration
Creation
Influence
The CR is to heavily dependant in the world and what the GM thinks. Look in chapter 8 where I mentioned above, and it gives guidelines for CR.
Also, you can just allow the player to do it without a roll at all. Every roll matters, so if you feel the character would be able to do it because of their background or feats or perks, just allow them.
I know that I come to this forum to ask questions about rules often (probably from my RP background)… that being said, I sure enjoy the patience and guidance that the members give. So encouraging!
and, Perks and Flaws are specifically designed for the players and GM to work together to create new ones. So you could always make a specific Perk that fits your world for this too!