as salam alaikum
the Qur'an says: "And tell the believing women to restrain their looks and guard their chastity and do not disclose their beauty except what is apparent and hit their khimars over their bosom" (24:31).
Some scholars have interpreted the expression "do not disclose their beauty (zinah)" in reference to the hair also.
The khimar is a veil that covers the hair. Some have interpreted the "hitting over the bosom" of the khimar as "covering the face" indicating the passage of the veil from the top of the head to the chest but it is a minority view.
The Qur'an also says: "O Prophet! Tell your wives, your daughters and the women of the believers that they should draw lower upon themselves their jilbabs" (33:59).
The jilbab is a wide dress that should cover the hair also.
In both verses the reference is to "the believing women", so it is not to be taken as a cultural practice but religious one.
There are also several hadith explaining the necessity of covering of the head and hair.
With prayers for your success.