Humans are referred to as trees in The Word of God
When it comes to a tree it can be fruitful at times but at the same time it can be unavailing in certain aspects. These unavailing traits are what Christ is trying to Get rid of. These ungodly traits get in His Way of what He wastes to accomplish in our lives 
 Matthew 16:23

Matthew 16:23
Amplified Bible
23 But Jesus turned and said to Peter, “Get behind Me, Satan! You are a stumbling block to Me; for you are not setting your mind on things of God, but on things of man.”