Herb
Rosemary
Salvia rosmarinus · Lamiaceae
Also called: Rosmarinus officinalis (former name), Trailing rosemary (prostrate forms, S. rosmarinus 'Prostratus')
Rosemary (Salvia rosmarinus) is a low-water herb well suited to Tucson and the low desert. It thrives in full sun.
Rosemary at a glance
- Water use
- Low (established)
- Sun
- Full sun; in Tucson, morning sun with light afternoon shade (eastern exposure) is ideal to ease the intense low-desert summer sun, though established plants tolerate full sun.
- Mature size
- Upright forms 3-5 ft tall and wide; trailing/prostrate forms 1-2 ft tall, spreading 3-6 ft.
- Growth rate
- Moderate (faster once established).
- Bloom
- Pale blue to lavender-blue (occasionally white or pink cultivars), Blooms mainly winter to spring (often nearly year-round in mild Tucson winters).
- Cold hardiness
- Evergreen woody perennial herb, hardy to about 15-20 F; reliably perennial in Tucson (USDA 9a-9b). Upright forms are slightly less cold-tough than trailing types.
- Soil
- Lean, gritty, fast-draining soil; thrives in poor, rocky, alkaline desert soils. pH 6.0-8.0. Avoid heavy clay or caliche without amending for drainage.
- Native range
- Mediterranean basin (Southern Europe, North Africa)
- Best used as
- Culinary herb, Low-water ornamental shrub or evergreen hedge (upright forms), Erosion-control groundcover and bank/wall spiller (trailing forms), Pollinator and bee plant, Container plant
- Wildlife
- Flowers are a strong nectar source for bees and other pollinators; aromatic foliage is deer- and rabbit-resistant.
- Toxicity
- Non-toxic and culinary-safe for humans; generally regarded as non-toxic / safe around dogs, cats, and children.
How to grow Rosemary in Tucson & the low desert
Watering
Plant in spring (or fall) so roots establish before summer. Drought-tolerant once established: water deeply and infrequently, roughly every 7-14 days in summer and every 2-4 weeks in winter. Excellent drainage is essential, overwatering and wet feet cause root rot in the low desert.
Fertilizer & nutrients
Very light feeder. Little or no fertilizer needed in landscape settings; an annual light application of compost or a low dose of balanced fertilizer in spring is plenty. Over-fertilizing reduces aromatic oil and flavor.
Pruning & care
Prune/shear lightly after the main bloom and in spring to shape and keep growth dense; harvest sprigs year-round. Avoid cutting hard into old leafless wood, which is slow to resprout.
Notes
One of the toughest, most heat- and drought-adapted herbs for Tucson, doubling as an attractive low-water evergreen landscape plant on the AMWUA/Tucson low-water-use plant list. Upright forms make hedges; trailing 'Prostratus' is a top desert groundcover for slopes and walls. Botanical name was reclassified from Rosmarinus officinalis to Salvia rosmarinus. Not native.
Sources: University of Arizona Cooperative Extension - Growing Herbs in Tucson (extension.arizona.edu); AMWUA / Pima Smartscape Low Water Use and Drought Tolerant Plant List (pimasmartscape.arizona.edu); Royal Horticultural Society - reclassification of Rosmarinus officinalis as Salvia rosmarinus