Trunkola was a planet run by sentient trees. They were basically a Tree Species. Trunkola is a Federation planet located in Sector 34. (Star Trek: Phoenix-X)
The USS Phoenix-X mostly mentioned the Tree species' were in conversation. In 2376, the planet was threatened by a Borg attack. ("The Return of the Borg")
In 2378, the Tree species began using illegal watering technology. The Phoenix-X was sent to destroy the technology. ("Avalon Battlefield, Part I")
The Tree species hadn't decided to join the Federation until 2378.