A perennial herb that grows best in Zones 1-24, 30-45, oregano is popular in Italian, Greek, and Spanish cooking. Use its leaves fresh or dried. Many kinds are available; of these, Greek oregano is considered one of the most flavorful. The plants reach 2½ feet tall and spread at a moderate rate by underground stems. Set them out 1½ to 2 feet apart; keep flowers cut back to encourage bushiness.