Growing Hair in a natural manner ?

i have kept a short shoulder length hair till my school since my parents said that it made me look smart and that it was a good hairstyle for kids,but now that i am growing up and see my sister having long hair been braided ,i feel that even i want long hair like her so that i can style it the way i want to.so i want to know about ways to grow  long hair naturally  and without the use of any chemicals?how much time does it take to grow hair in a natural way .now i dont want my hair to grow like rapuntzel!