First, it is crucial to clarify the botanical name. The plant commonly known as rosemary was historically classified as Rosmarinus officinalis. However, recent taxonomic revision based on genetic evidence has reclassified it into the sage genus, and its accepted scientific name is now Salvia rosmarinus. This highlights its close relationship to other salvias. This evergreen perennial shrub is a member of the Lamiaceae, or mint, family, characterized by its square stems, opposite leaves, and aromatic oils. From a horticultural perspective, this Mediterranean native is adapted to sunny, well-drained, alkaline soils and is highly drought-tolerant once established.
The primary compounds that give rosemary its distinctive piney, peppery flavor and aroma are volatile oils, such as cineole, camphor, and pinene. The concentration and profile of these oils vary between cultivars, directly influencing their culinary application. For instance, varieties with higher camphor content can taste more pungent and resinous, while those with higher cineole are often considered more classic. The physical form of the leaves is also a key factor. Upright varieties typically have broader, thicker, and more succulent leaves that are easier to strip from the woody stem, making them ideal for chopping and robust dishes like roasted meats. Prostrate varieties often have smaller, tighter leaves that can be used whole as a fragrant garnish.
Among the upright, shrub-forming types, several cultivars are exceptional for culinary use. 'Tuscan Blue' is highly prized by chefs for its straight stems, large, flat, deep green leaves, and exceptionally rich flavor with low camphor content. Its vigorous growth habit also makes it a productive garden plant. 'Barbecue' is another excellent choice, named for its stiff, straight stems that are perfect for using as skewers for grilling, imparting a mild, sweet flavor to foods. 'Miss Jessup's Upright' is known for its particularly aromatic oils and strong vertical growth, making it a good candidate for a formal herb garden hedge while providing abundant leaves for the kitchen.
For the home gardener with limited space or who wishes to grow in containers, hanging baskets, or over walls, prostrate varieties are ideal. Salvia rosmarinus 'Prostratus' is the most common trailing form. It features smaller, grey-green leaves and a spreading habit that can cover several feet of ground. While its flavor is slightly milder, it is still perfectly suitable for cooking and provides excellent ground cover. Another attractive option is 'Golden Rain' or 'Aureus', which offers variegated green and gold foliage. This cultivar grows more slowly and can be less winter-hardy, but it adds brilliant visual interest to a container while remaining edible.
The successful cultivation of rosemary depends on replicating its native Mediterranean conditions. All varieties demand excellent drainage; raised beds or containers are often preferable in areas with heavy clay soil or high rainfall. They are sun-loving plants, requiring a minimum of six hours of direct sun daily. While generally hardy in USDA zones 8-10, many upright varieties like 'Arp' are bred for enhanced cold tolerance, potentially surviving in zone 7 with protection. Prostrate types are often slightly more tender. For most home growers, ensuring the plant never sits in waterlogged soil is more critical to its survival than moderate cold temperatures.
