Did Ian McKellen grow in his own hair after he becomes Gandalf the white?

No, Ian McKellen did not grow his own hair for the role of Gandalf the White in "The Lord of the Rings" films. Instead, the production team used wigs and hairpieces to achieve the character's iconic look. McKellen's transformation into Gandalf included extensive makeup and costume design, ensuring a distinctive appearance that matched the character's portrayal in J.R.R. Tolkien's work.