Androzani tree
From Tardis Wiki, the free Doctor Who reference
Androzani trees were one of the universe's most efficient fuel sources. In 5345 the Eleventh Doctor, Madge Arwell and her children, Cyril and Lily, visited a forest of Androzani trees on an unnamed planet just before they were harvested by acid rain. Madge carried the trees' life force to safety through the Time Vortex. (DW: The Doctor, the Widow and the Wardrobe)
