Rosemary, a culinary herb many of us use in our kitchens, is also a marvelous drought-tolerant landscape plant. A woody perennial shrub, Rosemary (Rosmarinus officinalis) is a Mediterranean native well suited to our Valley climate. Its genus name means “dew of the sea” because it grows well by the ocean where the mist supplies all of its water needs. But it also thrives inland in well-drained soil with just a little irrigation.
Thought to improve memory, rosemary was associated with weddings in the Middle Ages. The bride and groom and wedding guests would wear a sprig for remembrance.
An aromatic evergreen shrub, rosemary has leaves similar to pine needles which are green above and white below with short wooly hair. The flowers, white, pink, purple or deep blue, appear in spring and summer but the plants can be in constant bloom in warm climates. Once established, rosemary can withstand drought for lengthy periods.
Rosemary has two basic growth forms: erect and trailing. The erect varieties are generally hardier, but the prostrate forms are hardy above 20 degrees if grown in well-drained soil. I have never had frost damage in my trailing rosemary.
Among the erect varieties are Blue Spires, growing 5 to 6 feet high and wide with deep blue flowers, and Albus, a 6-foot shrub with white flowers. Golden Rain is a bushy 3- to 4-foot variety with golden tinges on its leaves. Blue Boy makes a dense mound only 12 inches high, resembling a dwarf spruce. Hill Hardy grows up to 5 feet high with light blue flowers which repeat-bloom in the fall.
Among the trailing varieties, Huntington Carpet spreads quickly in a very dense 1½-foot high form—a great ground cover for banks. Irene is also a vigorous spreader with deep lavender blue flowers; it is also quite cold hardy. Prostratus is around 2 feet high, spreads 4 to 8 feet, and will root where the branches touch the ground. This variety can be so dense, it crowds out weeds! Prostratus also blooms in waves from fall though spring.
Easy to grow, rosemary only needs a sunny location, good drainage, and light soil. In our area it will withstand extreme heat and poor alkaline soil if given moderate water and infrequent feedings. Rosemary is generally hardy in the Valley, if its feet are not wet in the winter.
Rosemary is mostly pest-free. Powdery mildew can be a problem if conditions are humid, not usually a problem in the Valley. We have seen spider mites on some shrubs, but the plant does not seem to be harmed and a spray from the hose takes care of the webs.
Rosemary plants are widely available in nurseries and can also be started from existing shrubs. Propagation by cuttings of soft, new growth from an established plant is a good way to start a new plant. With the trailing varieties, a rooted section where the branch laid on the ground can be dug up, trimmed and planted out with generous water until the new plant is established.
Growth can be controlled by frequent tip pinching when the plants are small and light pruning of larger shrubs. Aside from culinary uses, Rosemary can shape our landscapes in many ways. It is often used in large settings where low water use is essential; check out the expansive, lush plantings at Visalia’s Riverway Sports Park. The taller varieties can be clipped into hedges and even used in topiary; the lower ones decorate dry gardens and act as borders. Trailing rosemary is a great ground cover and bank stabilizer. The blossoms attract butterflies, birds and bees and produce good honey.
Give rosemary a try if you have a problem area or just want a handsome, aromatic shrub in your landscape.
The Master Gardeners will be live to answer your questions on Saturday, July 2, from 8 to 11 a.m. at the Visalia Farmer’s Market in the southwest parking lot of Sequoia Mall. They can also be contacted between 9:30 and 11:30 a.m. on Tuesdays and Thursdays to answer your questions at 559-684-3325, or visit their web site at ucanr.edu/sites/UC_Master_Gardeners.