Vitamin C is one of the most effective nutrients to help grow and strengthen hair, says Loving. To give your locks a vital dose of vitamin C, blend a partially-boiled sweet potato, a half-cup of gooseberries, three strawberries, and half a small red bell pepper until you get a creamy smooth mixture. Then apply it to your scalp and hair. Leave the mask on for 15 to 25 minutes, then rinse it off with warm water.