Time Tree

The Time Tree was a tree which enabled time travel. It was possible to time travel simply by plucking its seeds, which grew into other time trees. However the method of time travel was not exact. One seed could take someone back a thousand years, another ten thousand. Time Trees had an appetite for heavy metals. Their leaves were orange. (PROSE: Genocide)

The Eighth Doctor stated that the Faction Paradox created (and planted) the trees.

They originated on the planet Hirath. (PROSE: Longest Day)