The Birnam Oak and Macbeth

"Macbeth shall never vanquish'd be until Great Birnam wood to high Dunsinane hill shall come against him." Shakespeare. Macbet Act 4 Scene 1
The Birnam Oak, next to it the Birnam Sycamore, are the last vestiges of an ancient forest, which Shakespeare referred to as the Birnam Wood.
Malcolm's army used greenery from the Birnam Wood to camouflage themselves to stage an attack on Macbeth at his Dunsinane stronghold.
It is also known as Macbeth's Oak.