Rosemary, a culinary herb that many of us use in our kitchens, is also a wonderful drought-tolerant landscape plant. Rosemary (Rosmarinus officinalis), a woody perennial shrub, is a Mediterranean native well suited to our valley climate. Its generic name means “dew of the sea” because it grows well by the ocean, where the mist provides all of its water needs. But it also thrives inland in well-drained soils with little irrigation.
Rosemary is believed to improve memory and was associated with weddings in medieval times. The newlyweds and the wedding guests carried a branch as a reminder.
An aromatic evergreen shrub, rosemary has pine needle-like leaves that are green above and white below, with short woolly hairs. The flowers, white, pink, purple, or deep blue, appear in spring and summer, but the plants can bloom continuously in warm climates. Once established, rosemary can withstand drought for extended periods.
Rosemary has two basic growth habits: upright and pendulous. The upright varieties are generally sturdier, but the prostrate forms are hardy above 20 degrees when grown in well-drained soil. I’ve never had frost damage in my hanging rosemary.
Among the upright varieties are Blue Spiers, which grow 5 to 6 feet tall and wide with deep blue flowers, and Albus, a 6-foot tall shrub with white flowers. Golden Rain is a bushy 3 to 4 foot tall strain with golden highlights on the leaves. Blue Boy forms a dense mound just 12 inches tall that resembles a dwarf spruce. Hill Hardy grows up to 5 feet tall with light blue flowers that bloom repeatedly in the fall.
Among trailing cultivars, Huntington Carpet spreads quickly in a very dense 1 1/2 foot tall form—a great bench groundcover. Irene is also a vigorous spreader with deep lavender blue flowers; it is also quite hardy. Prostratus is about 2 feet tall, spreads 4 to 8 feet, and roots where the branches touch the ground. This strain can be so dense that it crowds out weeds! Prostratus also blooms in waves from fall through spring.
Rosemary is easy to grow and only needs a sunny spot, good drainage and light soil. In our area, it can withstand extreme heat and slightly alkaline soil with moderate watering and infrequent feeding. Rosemary is generally hardy in the valley if its feet are not wet in winter.
Rosemary is largely pest-free. Powdery mildew can be a problem when conditions are wet, usually not a problem in the valley. We have seen spider mites on some shrubs but the plant does not appear to be damaged and a spray from the hose takes care of the cobwebs.
Rosemary plants are widely available in nurseries and can also be grown from existing shrubs. Propagation by cuttings from soft new growth of an established plant is a great way to start a new plant. For the hanging varieties, a rooted section where the branch is lying on the ground can be dug up, trimmed and planted out with plenty of water until the new plant is established.
Growth can be controlled by frequent top pinching when plants are small and light pruning of larger shrubs. Aside from culinary uses, rosemary can shape our landscapes in many ways. It is widely used in large environments where low water consumption is required. Check out the sprawling, lush plants at Visalia’s Riverway Sports Park. The larger varieties can be cut into hedges and even used as a topiary; the lower ones adorn drying gardens and act as boundaries. Trailing rosemary is a great groundcover and bank stabilizer. The flowers attract butterflies, birds and bees and produce good honey.
Give rosemary a try if you have a problem area or just want a beautiful, aromatic shrub in your landscape.