I have seen many Sadhu who grow their hair and never cut them, while there are some Pandits who shave their hair and just have a small pony tail. Both of them are devotees of God but have opposite traits for their hairs.
Adding more on this, Hindus have a custom/belief/superstition until 'Mundan ceremony' is done, people avoid making a child pass under the shade of a tree as his hairs have not been shaved and they are prone to catching spirits. Also, in jainism (which is a near hinduism religion) there are stories of people plucking all their hairs and attain Dikhsha for Sanyaas. In Hinduism, people shave their hairs when their parents die. People also get hairs shaved in some famous temples like Tirupati Balaji, Mata Chintpurani, etc. There is also a strong belief that while praying or doing something hawan, etc, we tend to cover our hairs.
I want to know if there is a reason/belief for growing or cutting of hairs?