Young Adult, Trees

I only know the most vague details of a sci-fi book that I read in the early 2000s, but I don’t believe it was a new book then. I think the cover was green, paperback for sure.

I only remember that they ate the insides of a tree or plant, the insides were fruit like, and I am fairly positive that they were hiding inside those very tree/plants, eventually needing to move on after an event/choice.

I’m not saying that it isn’t Midworld, but Google never answers that specific detail.

Thank you 🥰