Androzani Pine Trees are a form of sapient vegetation from the Androzani system. They physically resemble the pine trees from Earth, and likewise form huge forests in the snowy regions of a planet, implied to be Androzani Minor.
The natives of Androzani Major, apparently unaware of the trees' intelligence, use them to produce fuel. The trees possess a hive mind and act as a single organism, being able to direct their own growth to form intricate structures of wood, even functional starships. However, they are restricted to their sessile bodies unless able to find a compatible host to which they can temporarily transfer their life essences. This host body, for unclear reasons, must be an adult female.
The trees also exhibit awareness of future events, being able to predict that in the year 5345, the people of Androzani would use acid rain to melt the entire forest. Fortunately, the Doctor opened a spacetime portal to their planet on that very year, from Earth 1941. He intended to visit the planet with Madge Arwell and her children, Cyril and Lily, to entertain them on Christmas day. As it turned out, Madge proved a suitable host and was able to transport the conscience of the Androzani trees through the Time Vortex, where they left her body and ascended to a non-corporeal existence, becoming star-like beings.
- Doctor Who, 2011 Christmas special "The Doctor, the Widow and the Wardrobe"