Tree of Cheem

The Tree of Cheem were a race of intelligent humanoid trees, descended from the rain forests of Earth.

Biology
The Trees of Cheem were humanoids with large, intricate heads, and wood-like skin. They had retractable vines on their arms called lianas, which they weren't supposed to show in public. The Trees of Cheem were made of wood and were therefore highly flammable. (DW: The End of the World)

Culture
The Trees of Cheem did not understand technology, referring to computers as "metal minds" or "metal machines", but they were known to use it. They kept clippings of their relatives, occasionally giving them as gifts. According to the Ninth Doctor, they were of huge financial importance due to their land holdings and forests on various planets, and they had "roots" everywhere. (DW: The End of the World)

History
During the Middle Blue Period of Earth, the Brothers of Hame brought a 500x300 mile plot of trees from the rain forests on Earth to the Panjassic Asteroid Field, where the trees' evolution was accelerated from a billion years to just three years. Collectively, the Trees of Cheem turned against their creators and fled into space in spaceships made from bark. Two hundred years after the experiments, they had chosen the name Forest of Cheem for themselves, taking the name from their word for water. (REF: Doctor Who: Monsters and Villains) Cheem was also the name for the planet where the Forest would live. (TDL: The Game of Death)

Five thousand years later, the Trees of Cheem were considered to be one of the higher species and were witnesses to the last great Time War. They were aware of the course of the war and its history-changing effects and were mortified by the bloodshed. (DWAN: Doctor Who Annual 2006)

During the destruction of Earth in 5,000,000,000, a group of trees were found on Platform One, due to the Forest of Cheem's wealth. The group of Trees seen on Platform One was led by Jabe Ceth Ceth Jafe and also included Coffa and Lute. (DW: The End of the World)

At some point after the destruction of Earth, Coffa and Lute were menaced by some unknown force who was hunting down the survivors of Platform One. When they tried to warn the Tenth Doctor and Rose Tyler, they were discovered by Montodon Slemm, who intended to capture them for resale. Though the Doctor and Rose were able to stop Montodon, Coffa and Lute were captured by the Elth of Balhoon in the confusion. (DWBIT: Growing Terror) Elth held the survivors of Platform One responsible for his brother's death and planned to kill them in revenge. When the truth came out, Coffa and Lute agreed to plant a garden in remembrance. (DWBIT: Reunion of Fear)

Unknown Dates

 * Several Trees of Chem helped the Doctor collect black crystals called Time Shards (VG: Worlds in Time)