Ocimum basil is an annual, or sometimes perennial, herb used for its leaves. Depending on the variety, plants can reach between 30 cm (0.98 ft) and 150 cm (4.9 ft). Its leaves are richly green and ovate but otherwise, come in a wide variety of sizes and shapes depending on cultivar. Leaf sizes range from 3 cm (1.2 in) to 11 cm (4.3 in) long, and between 1 cm (0.39 in) and 6 cm (2.4 in) wide.
Basil grows a thick, central taproot. Its flowers are small and white and grow from a central inflorescence that emerges from the central stem atop the plant.