There are so many plants that are called oregano that some suggest oregano be considered a flavor rather than a particular species. Nonetheless, there are two kinds of oregano that are often used in the kitchen. Both are herbaceous perennials. The most popular is Origanum vulgare, or Mediterranean oregano, which is a member of the mint (Lamiaceae) family. It's also called true oregano, or Greek oregano. The other is Lippia graveolens, or Mexican oregano, a member of the Labiatae family.