What is the significance of Malcolm's army carrying branches from Birnam
wood to the castle?

your mom

Explanation:

Malcolm suggests that his army cut down branches from Birnam Wood and hold them up to remain hidden as they march towards Macbeth's castle. The 3rd apparition said that Macbeth will only be defeated when Birnam Wood marches towards him and when the soldiers hold the branches it will look like the woods are marching.

Explanation:

if you want me to check your answer i agree with what you put. i read the story