Rosmarinus officinalis or Rosemary is an aromatic, evergreen shrub native to the Mediterranean region. Shrubs will reach 2-6 feet (0.6-1.8 m) with a spread of 4-5 feet (1.2-1.5 m). Leaves are leathery, linear to 0.5-1.5 inches (1.3-3.8 cm) long. Leaves are green above and gray green underneath. The fresh flowering tops are used to distill the aromatic oil that is used in perfumery and medicine. Dried leaves are used as a seasoning. Plants in warm climates are used as hedge material or as a single specimen, in cooler climates they are used as a container plant. Plants are very easy to grow whether in the landscape or in containers. They are hardy in the landscape in USDA zones 8-10.
Blooming: In the greenhouse and in milder climates the plants bloom in late winter through spring. The pale blue flowers are about 1 inch (2.5 cm) long.
Culture: Rosmarinus officinalis needs at least 6 hours of full sun per day and a very well drained soil mix. In the greenhouse, we use a soil mix consisting of 1 part peat moss to 2 parts loam to 2 parts sand with small gravel added to ensure drainage. Also to this mix, we add 1 cup of ground limestone to each 0.01 cu. yards of mix. This is added to ensure that the mix is not too acidic. Plants are well watered and allowed to dry thoroughly before watering again. We fertilize only once during the growing season with a balanced fertilizer. In the landscape once plants become established they are very drought resistant. During the winter months in the greenhouse, plants are kept in the cool rooms where nighttime temperatures fall to 48°F (9°C). Water is restricted to only enough to keep the leaves from dropping.
Propagation: Rosmarinus officinalis is propagated by cuttings taken in spring after flowering, by layers and from seed.
Rosmarinus officinalis was featured as Plant of the Week June 19-25, 2009.
Guide to Past Plants-of-the-Week:
Cal's Plant of the Week was provided as a service by the University of Oklahoma Department of Microbiology & Plant Biology and specifically the late Cal Lemke, who used to be OU's botany greenhouse grower and an avid gardener at home as well. If the above links don't work, then try the overview site. You may also like to look at the thumbnail index. ©1998-2012 All rights reserved.