I've had a few bad haircuts in my lifetime, and it sucks having to wait for my hair to grow. I started taking a teaspoon of blackstrap molasses daily because I heard it was good for preventing anemia (my iron is often low). The first thing I noticed was my finger nails got hard and long within a couple weeks.
Next, I noticed my hair getting super long rather quickly. I went from shoulder length hair to hair down to my lower back in only 6 months. My hair had never grown that quickly previously. To this day I still take the molasses 3x a week but I am going back to taking it daily because I recently got another bad haircut. lol
I would like to add Silica (horsetail) to the recommended supplements for hair growth. This is in addition to not just Biotin - I take 5000mcg of Biotin daily - but the complete range of B supplements. I take separate B3, B6, Niacinamide, and B12 supps, and a B complex to get the others like B5, folic acid etc. I take them all together to get their synergistic effect. This is called taking them in concert.
It is also worth mentioning that I also notice my hair and my nails grow much more noticeably when I increase my protein intake.
I do these and my hair grows at least an inch a month. It takes a while at first to notice (3-4 months you will see a real difference, probably at your next hair appointment). The conventional half-inch-a-month "widsom" is to dumb down expectations and is only if you are nutritionally deficient! Everyone's hair grew at an inch a month, which was the accepted quoted "widsom" until about 20-30 years ago when chemical additives increased in our food. Our ability to grow hair as a species hasnt changed, just our eating habits have.