I'm sorry, but I must state that Saiyans hair DO NOT grow. They made this a fact in the anime, I'm not sure about the manga though, but I'm pretty sure they say the same.
Yea but goten is a half he has human genes so his hair does grow because he picked up that human trait from chi chi
ExactlyGohan's hair grew during DBZ and Goku had to cut it
And...what's your point? Goku had to cut Gohan's hair? You know, sometimes, in human life, the hair doesn't grow back. I learned that from experience.