Rosemary Plant in the High Desert

Climate

• The Mediterranean climate where rosemary is native has hot, dry summers and cool, rainy, frost-free winters. Although rosemary can take light frost and short periods below 20 degrees Fahrenheit, it will die back with long, hard freezes. Rosemary will benefit from afternoon shade in the hotter high-desert areas. It can be grown in a protected area in the higher parts of the Sonoran Desert and should be grown in a pot and taken inside for the winter in the Great Basin high desert.

Soil

• Rosemary thrives in well-draining, alkaline soil, which is typical for high desert areas. There is little need to fertilize the shrubs except in the poorest soil. When growing rosemary in pots, use a large pot and a light potting soil with a little sand mixed with it.

Water

• Although rosemary does best in well-draining soil, it has many small, fibrous roots. If they are allowed to dry out completely, the plant will die. Regular watering is essential. Soak the soil thoroughly whenever the top 2 inches of soil is dry. The Master Gardeners of Santa Clara, California, recommend watering every three weeks, but rosemary may require more frequent watering in hotter, drier areas.

Pests and Diseases

• Rosemary is a relatively problem-free shrub. Aphids, spider mites and spittle bugs can sometimes be found on rosemary. They can all be controlled by washing the shrub with a strong stream of water. Powdery mildew can be a problem if there is poor air circulation. Prune the plant to open it up and improve air circulation. If the soil is too wet, the plants can get crown and root rot. Avoid overwatering or too frequent watering.