Basil (Ocimum basilicum) is one of the most popular herbs in the world. Its most common cultivar, sweet basil, is known for its timeless flavor.The leaves have warm, spicy flavor. (Nothing beats homegrown tomatoes sprinkled with fresh basil.) Many more basil cultivars have become popular in recent years and bring unique tastes to the kitchen. This annual herb is easy to grow and makes a great companion plant to tomatoes, asparagus and other vegetables.