Optimum Soil Conditions for Rosemary

Types of Rosemary

• There are two main types of rosemary plants. There is the upright type (Rosmarinus officinalis) and the creeping or prostrate type (Rosmarinus officinalis 'Prostratus'). The creeping type of rosemary has a low-growing habit allowing it to cascade over walls or the sides of containers. The upright type has strong upward growth and some varieties can reach 6 feet tall. When purchasing rosemary, be sure you choose a variety that suits your landscaping needs.

Optimal Soil Conditions

• Rosemary grows best in light, well-drained soil that allows water to drain easily away from the root system of the plant. Heavy clay that holds water after a rain will eventually kill rosemary. If growing in containers, use a well-draining planting mix and a container with drainage holes. The optimal soil pH for rosemary is between 6 and 7.5. If the soil pH is below 6, the soil can be amended with agricultural lime. A soil test will help determine which amendments you need. For assistance with a soil test, contact your county agricultural extension office.

Planting Tips

• Plant rosemary in the spring in a location that receives at least six hours of full sunlight each day. Rosemary grows quickly, so space plants according to their mature size. If your soil is sandy, incorporate a 1-inch layer of well-rotted compost into the top 6 inches of soil before planting. If the soil is heavy clay, consider building a raised bed and filling it with appropriate well-draining soil. Although a layer of mulch will conserve moisture and prevent weeds around the rosemary plant, keep in mind that mulch prevents drainage of moisture that causes fungal and mildew disease.

Rosemary Plant Care

• If desired, prune rosemary after the bloom period. It can be sheared to a dense hedge or allowed to sprawl depending on the variety. Rosemary will die if overwatered, so allow the soil to dry out between watering. Rosemary will also die in extreme drought conditions or where the climate is very dry. Give the plant supplemental water if the foliage appears to by drying during an extended dry period. Spider mites, which cause yellowing of the leaves, can be controlled by spraying the underside of the leaves with a strong blast of water.

Harvesting Rosemary

• Harvest rosemary anytime by cutting an entire limb where it attaches to a main branch. Immediately remove the leaves from the stem for fresh use. Dry rosemary by hanging the stem in a dark, dry place before removing the leaves. Drying in a dark location helps to preserve the green color of the plant.