I listen to a lot of audiobooks from my library. I really enjoy Hillary Huber, who’s a voice actor who reads books. She’s narrated a couple of light mystery series that I’ve particularly enjoyed – she’s got a great repertoire of character voices. In my library, I can look up audiobooks by their narrators.
The S-Town podcast is about 7 hours long, but yes, that is on the shorter side when compared to audiobooks.
We’ve listened to some Ken Follett books on long cross-country car trips. He might enjoy the Century Trilogy? Books are Fall of Giants, Winter of the World, and Edge of Eternity.
A couple of novels that feature plants that I can recall are State of Wonder by Ann Patchett, and The Poisonwood Bible by Barbara Kingsolver.