There are several different good essential oils that will help with promoting hair growth but the best essential oil that I've found to promote hair growth the best is Lavender Essential Oil.
I've tried many other essential oils for hair growth and they do all work but the Lavender Oil helped grow the hair faster than the other oils.
Other good oils that do help promote hair growth though are, Clary Sage Oil, Thyme Oil, Lemongrass Oil, Cedarwood Essential Oil, Peppermint Oil, Rosemary Oil and Horsetail Plant Oil.
All those essential oils will promote hair growth but I would recommend the Lavender Oil for best hair growth.