Elm
From Memory Alpha, the free Star Trek reference.
The elm is a large deciduous tree native to planet Earth.
A large elm tree with a circular bench was located on the Starfleet Academy grounds in San Francisco. It was located close to the parade grounds. Jean-Luc Picard and Simon Tarses used to sit under that tree during their Academy days and watch and study. (TNG: "The Drumhead")
It was possibly the bark of this prized elm tree, cherished by Boothby, that Cadet Picard carved the initials A.F. into. (TNG: "The Game")
When Captain Kathryn Janeway asked a holographic Leonardo da Vinci what he imagined his life would be like if he were a sparrow, he replied that he'd make his home in a tree, in the branch of an elm and would hunt insects for food, straw for his nest and in the springtime he would sing for a companion. (VOY: "Concerning Flight")
