The most commonly used basil variety for making pesto, you can harvest these leaves as soon as they are large enough to consume. Genovese basil is also known as "Sweet Basil" and a common ingredient to all Italian dishes. The leaves are spoon-shaped, glossy, and a dark green shade.   It grows best in organic-rich and well-drained soil and is an easy-to-grow annual herb that thrives in areas that remain above 50 degrees Fahrenheit.