The Tree species were a civilization of tree-like creatures within the Federation. Most individuals were confined to the ground, and unable to relocate, on their home world, Trunkola. (Star Trek: Phoenix-X)
History
In 2376, the tree-people were enemies of the Helenion's and the Federation. Much of the guff would be from people attempting to steal from their planet. ("Christmas Special")
In 2378, the tree-people of Trunkola made use of illegal watering technology when they joined the Federation. They were easily thwarted by efforts from the Phoenix-X. ("Avalon Battlefield, Part I")
In 2382, the tree-people begun space travel for the first time in their history. It is presumed they somehow created their own starships. ("Spider Agencies, Part I")