Plant rosemary (Rosmarinus officinalis) during the mild spring and fall weather, or in winter in frost-free climates. If summer planting is unavoidable, plant early in the morning when the air is still cool. This Mediterranean native grows in U.S. Department of Agriculture plant hardiness zones 8 through 10. Outside of the growing region you can grow this perennial shrub as an annual herb by planting in the spring after the last frost and harvesting the whole plant before the following winter.
Full Sun and Good Drainage
Plant rosemary in a sunny garden bed that gets six or more hours of sun per day. Drainage is critical for rosemary. Avoid areas where water stands after a rain or at any time during the year. This Mediterranean native will rot in cold, wet soil.
For gardens with clay soil or poorly drained areas, grow rosemary in a 12-inch-tall or taller raised bed to help with drainage around the roots.
Pre-Planting Soil Preparation
Mix organic material -- like compost or seasoned manure -- with the soil in the bed before planting. Use a 4-inch-deep layer dug 6 to 8 inches into the top of the soil. This improves drainage, aerates the soil and provides natural nutrients. Rosemary prefers soil with a pH between 6.0 and 7.0.
In raised beds, fill with quality topsoil then finish off the last 4 inches with compost or manure. Blend the materials with a garden fork before planting.
Proper Planting and Spacing
Hollow out a hole in the prepared bed the same depth as the root ball. Set the rosemary plant in the hole, keeping the base of the woody trunk at the soil line, then fill in the soil around the edges of the roots. Avoid planting rosemary too deep. If the base of the trunk sits below the soil line, the plant can rot.
Space rosemary plants between 1 and 4 feet apart. Rosemary is a perennial shrub that grows up to 6 feet tall and 4 feet wide in mild climates. Space the plants 3 to 4 feet apart in frost-free areas so they have room to grow. If you're growing rosemary as an annual outside of the growing region, set them 1 to 2 feet apart as they rarely grow more than 1 to 2 feet in a single season.
Watering New Rosemary Plants
Water a newly planted rosemary right away, even if its damp and overcast. Soak the soil slowly to the depth of the planting hole. Keep the soil moist for the first one to two months after planting, watering when the top 1 inch of the soil dries slightly. Once established, rosemary only needs water twice a month.