Doctor Who: The Roots of Evil: 09/18/16
Doctor Who: The Roots of Evil by Philip Reeve is a Fourth Doctor story, written for the 50th anniversary. It features Leela as the companion, with a brief, off screen, cameo by K9. There is also a nod to the Tenth Doctor.
In "Time of Angels" (series 5 of the reboot), part of the adventure takes place on the Byzantium, a spaceship that contains a forest used for creating oxygen during deep space journeys. In The Roots of Evil the Doctor and Leela encounter a world made entirely of wood, an overgrown singular tree that has become the entire world for the many generations dependents of one of these ships.
They also, though, have a long standing anti-Time Lord culture, specifically, anti-Doctor. His arrival has sparked a civil war between those who want him executed and those who wish to move on from that long standing sentence.
There's a bit of wibbly-wobbly timey-wimey reason behind the sentencing and the mutation of the spaceship. The wheres and the whys are a big part of the fun of this short story.