Growing Rosemary - November 25, 2015
Jeff Schalau, Agent, Agriculture & Natural Resources
University of Arizona Cooperative Extension, Yavapai County


Rosemary (Rosmarinus officinalis) is an attractive, drought tolerant perennial plant that should be part of everyone's landscape or herb garden. Rosemary is a member of the mint family (Labiatae) and comes from the Mediterranean region where it often grows on cliffs near the ocean. It is hardy to 10 degrees F as long as it has some time to slowly harden off in the fall. It survives Prescott, Arizona winters (USDA Hardiness Zone 7b) and usually does very well when planted in the Verde Valley.

The most common varieties have blue flowers and are either the prostrate growth form (1 to 2 feet in height) or the upright growth form (3 to 6 feet in height). Rosemary is available in other flower colors: including white and pink. Many of these varieties were developed by European horticulturists and may have to be mail ordered in Arizona. I would only recommend fancy varieties for people that are interested in odd plants. The blue flowered varieties are better adapted and blue flowers are usually uncommon in most gardens.

The Mediterranean climate has mild winters with moderate precipitation and hot, dry summers. This is very similar to many parts of California. It's no accident that many California landscapers utilize several Mediterranean plant species and this plant palette has also been successful in Arizona (lavender, olive, grape, cypress, etc.).

Rosemary can be grown from seed, but named cultivars grown by major nurseries are always grown from cuttings. When purchasing them, I often look for 4-inch pots in the herb section of the nursery. They should be planted in well-drained soil. The upright varieties make a good, informal evergreen hedge. If pruning is required, upright plants should be selectively pruned rather than sheared. Prostrate forms look best in cascading over masonry or rock walls or in rock gardens where the individual branches create interesting edge patterns. These can also be shaped easily by selective pruning.

Even though rosemary is "drought tolerant" it still needs some irrigation. I suggest giving plants frequent water (every 3 to 5 days) during the establishment phase and then decrease irrigation frequency once the plant has grown for a few months and the root system has expanded. In my experience, rosemary plants that survive the first year will live for a long time. Excessively irrigated plants can become very woody. Rosemary planted in native soil usually need no supplemental fertilizer and minimal irrigation after establishment. May and June are the most critical months to maintain irrigation. After the monsoon season gets started, rosemary will not need supplemental water except for during very hot, droughty periods.

You may have noticed an emphasis on the health benefits of a Mediterranean diet lately in the media. Rosemary should be dried before use and a little goes a long way. To do this, cut a few branches in the morning, then hang them to dry in a ventilated area out of direct sunlight. Once it is dried, simply rub the branches to separate the leaves from the stem and store leaves in a sealed glass jar. Use as a flavoring herb for roasted fish, chicken, lamb, beef, game, in soups and stews, and on oven-roasted potatoes.

The Romans and Greeks used rosemary and often associated it with love and the deities Eros and Aphrodite. Other references say that it is an effective insect repellent and that rosemary oil applied externally has cancer prevention properties. Browsing wildlife species are usually repelled by its pungency as well. Note: the oil should not be taken internally. Even small doses can cause stomach, kidney and intestinal problems, and large amounts may be poisonous. Scientists at the University of Cincinnati say that the scent of rosemary is an effective memory stimulant. I should put a potted plant at my desk at work (if I can remember to water it).

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Additional Resources

Rosemary
University of Illinois Extension

extension.illinois.edu/herbs/rosemary.cfm

Easy Gardening: Rosemary
Texas A & M Agrilife Extension

aggie-horticulture.tamu.edu/vegetable/files/2010/10/E-623-Easty-Gardening-Rosemary.pdf

How do I propagate my rosemary plant?
eXtension

articles.extension.org/pages/34431/how-do-i-propagate-my-rosemary-plant#.Vktmfr-vMqg

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Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr. #C
Prescott, AZ 86305
(928) 445-6590
Last Updated: November 25, 2015
Content Questions/Comments:
jschalau@ag.arizona.edu
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