Origanum vulgare, also known as wild marjoram, is the species which is most often sold commercially as oregano. There has been a long-standing debate about which species of Origanum should rightly be referred to as common oregano. Oregano is a bushy, semi-woody sub-shrub with upright or spreading stems and branches. Some varieties grow in mound like mats, spreading by underground stems (called rhizomes), and others with a more upright habit. The aromatic leaves are oval-shaped, about 1.5 in (3.8 cm) long and usually pubescent (fuzzy). Throughout the summer oregano bears tiny purple tube-shaped flowers that are about 1/8 in (0.3 cm) long. These peek out from whorls of purplish-green leafy 1 in (2.5 cm) long bracts that resemble little pinecones. Oregano is from the Mediterranean region of Europe and Asia. It has become naturalized in much of eastern US, where it is called wild marjoram. Oregano prefers full sun. It is said that the pungency of oregano is directly related to the amount of sun it gets.
Origanum vulgare - Floridata, http://www.floridata.com/Plants/Lamiaceae/Origanum%20vulgare/610 (accessed January 24, 2017).