Greek oregano, known botanically as Origanum vulgare ssp. hirtum, is a hardy herbaceous perennial. This means the herb is reliably capable of surviving the winter months and returning to grow again the following spring. Its natural resilience allows it to thrive for many years, providing a continuous source of pungent foliage. Its perennial nature makes it a staple in many temperate herb gardens.
Defining True Greek Oregano
The identity of true Greek oregano is often confused with its milder relatives, making the botanical distinction important. The authentic culinary variety, Origanum vulgare ssp. hirtum, is recognized for its robust, spicy, and slightly peppery flavor. This intensity comes from a high concentration of essential oils, particularly carvacrol, which can be up to 80% of its oil content. Common oregano (Origanum vulgare) contains much less carvacrol and offers a milder, grassier taste.
A simple visual difference is the flower color: true Greek oregano produces small white blossoms, while the common variety typically has pink flowers. Plants sold as “Mexican oregano” are from an entirely different genus (Lippia graveolens) and are not closely related to the Mediterranean herb.
Perennial Growth and Hardiness
Greek oregano is reliably perennial across a broad range of temperatures, thriving in USDA Hardiness Zones 5 through 10. In these zones, the plant survives the cold by entering a state of dormancy during the winter months. The above-ground foliage, which is soft and green during the growing season, will begin to brown and die back after the first hard frost. This process concentrates the plant’s energy into the root system.
The plant appears woody and lifeless during the coldest parts of winter, with old stems serving as a protective layer for the root crown just below the soil surface. This dormant state allows the root mass to endure temperatures that can dip to approximately -20°F. As the soil begins to warm in the spring, new, tender green shoots will emerge directly from the base of the plant, signaling the return to active growth.
Cultivation for Year-Round Survival
The quality of its drainage is the most important factor for ensuring Greek oregano survives year-round, especially in winter. The plant is adapted to the dry, rocky soils of the Mediterranean, and wet winter soil is the primary cause of root rot and plant loss. Planting in a location with excellent drainage, such as a raised bed or soil mix amended with sand or grit, is necessary to prevent the roots from sitting in soggy conditions.
Pruning for Vigor
To maintain the plant’s vigor, active pruning is required to remove old, woody growth. Stems should be cut back to within two or three inches of the ground in late fall after the first frost, or in early spring before new growth begins. This hard pruning stimulates fresh, non-woody growth from the root crown, which is the most flavorful part of the herb. Avoid trimming in late summer, as the plant needs time for new growth to harden before winter.
Winter Protection
In the colder parts of its hardiness range, applying a two to three-inch layer of dry mulch, such as straw or shredded bark, provides additional insulation. Apply this mulch only after the ground has frozen to prevent rodents from nesting. For gardeners in zones colder than 5, or for container-grown plants, overwintering indoors is a simple solution. Move the potted herb to a cool, bright area, like an unheated garage or a sunny window, and water very sparingly until spring arrives.