By Dr. William C. Welch,
Many landscape plants suffer during the dry heat of August, but rosemary (Rosmarinus officinalis) thrives on it. Although usually cold-hardy in South Texas, some winter protection may be needed elsewhere in the state. Rosemary grows well even in poor, dry, rocky soil as long as drainage is good.
The evergreen character of the narrow foliage and many horticultural forms of the plant make it quite useful. Prostrate selections are good for ground cover or spilling over retaining walls. Mature height ranges from 18 inches to 4 feet, depending on the variety and growing conditions. Small lavender-blue flowers in spring and summer are attractive but not spectacular. A major attraction of rosemary is the strongly scented foliage which is popular, fresh or dried, for seasoning. The fresh tops are reported to be used to distill the aromatic oil used in perfumery and medicine.
Rosemary has been a popular plant for centuries in Europe, and was often planted close to the entrance of homes in the traditional cottage gardens of England. When people passed by and brushed against a rosemary plant, the scent was released and enjoyed.
Rosmarinus officinalis is a native of the Mediterranean region. Typical of many plants in that part of the world, old specimens may be thinned to expose the gnarled stems, which create a bonsai-like effect.
Few herbs can compete with this plant for landscape value. Propagation is by seed or cuttings. With the renewed interest in herbs, many garden centers now stock rosemary. One-gallon-size plants establish quickly. Full sun or partial shade are both good exposures. The key to successfully growing R. officinalis is well drained soil. If your soil is not well drained, try growing the plant in a clay pot or whiskey barrel half. Recently, interest in trimming rosemary into various topiary forms has increased. Tree standards are particularly nice. ‘Arp’ is probably the most cold-hardy selection of rosemary.