Salvia rosmarinus
Family: Lamiaceae
Perennial Herb
This is a popular shrub with fragrant, evergreen, needle-like leaves and white, pink, purple, or blue flowers, native to the Mediterranean region. Until 2017, it was known by the scientific name Rosmarinus officinalis.
Forms range from upright to trailing—the upright plants can reach 3-4’ tall. The trailing rosemary is usually under 2’ tall but spreading very wide. Flowers are usually purple and show up in warm weather. But they can also be blueish, white or pink.
The first mention of rosemary is found on cuneiform stone tablets as early as 5000 BCE, after which Egyptians used it for embalming corpses starting in 3500 BCE. There is no further mention of rosemary until the ancient Greeks and Romans. Pliny the Elder (23–79 CE) wrote about it in The Natural History, as did Pedanius Dioscorides (c. 40 CE to c. 90 CE), a Greek botanist (amongst other things). He talked about rosemary in his most famous writing, De Materia Medica, one of the most influential herbal books in history.
USES
Aside from its usage in the fragrance industry, Rosemary is not only used as a decorative plant in gardens, but also cultivated for practical applications, such as medicine and cooking. When the plant is fully grown, the leaves, twigs, and flowering apices are often extracted for use in these areas. Rosemary leaves are used as a flavoring in foods, such as stuffing and roasted lamb, pork, chicken, and turkey. Fresh or dried leaves are used in traditional Mediterranean cuisine. They have a bitter, astringent taste and a characteristic aroma which complements many cooked foods. Herbal tea can be made from the leaves. When roasted with meats or vegetables, the leaves impart a mustard-like aroma with an additional fragrance of charred wood that goes well with barbecued foods.
Rosemary extract has been shown to improve the shelf life and heat stability of omega 3-rich oils which are prone to rancidity. Rosemary is also an effective antimicrobial herb.
PRESERVATION
Rosemary is easily dried and last quite a while, though the pungency of flavor is best used fresh.
GROWING
SEASON & PLANTING
Plants are available year round at nurseries and you can plant them any time of year. Most cultivars are maintained by cutting (asexual reproduction) and they can be finicky from seed, so getting plants grown by nursery professionals is probably best.
SOIL & NUTRITION
Rosemary isn’t picky about soil as long as the drainage is good. They are often grown as landscape plants with little or no soil amendment. But some preparation makes for healthier, tastier plants. Rosemary may grow well in your garden bed, but may take over, as plants are large shrubs or ground covers.
TEMPERATURE & SUN EXPOSURE
Plant rosemary in full sun. Too much shade makes rosemary susceptible to noctuid moth larvae. Afternoon shade is acceptable but not ideal. Rosemary is dependably hardy down to at least 10°F.
WATER
So long as the drainage is good, rosemary can handle regular watering. On the other extreme, they can handle typical landscape watering when established.
HARVESTING
Harvest branches or tips as needed.
WILDLIFE
As mentioned above, too much shade will encourage noctuid moth larvae. However plants will recover easily. They may get infested either way, and if they do, plants in the proper amount of sun will recover quickly.
INVASIVENESS
Rosemary does not seem to escape cultivation in our region.
POPULAR SELECTIONS
Most rosemary selections are one of two growth forms, upright or trailing, as mentioned above. Otherwise they are selected for leaf shape, flavor, or flower color.
Albiflorus rosemary cultivar growing up to 3’ in height and width. It shows beautiful white flowers and short dark green foliage.
Blue Tuscan with its vividly blue flowers and large, tender foliage, and reaching a height up to 4’, this variety makes a wonderful specimen in the garden. It is also excellent for using in the kitchen.
Gorizia growing up to 4’ tall, it makes an excellent shrub in your garden. It has very pale violet-blue flowers and dark green foliage.
Heavenly Blue as a very compact grower, only reaching up to 1.5’ tall, this variety is perfect for borders in your garden or for growing in a pot. It has pale blue flowers and lovely green foliage.
Huntington Carpet a prostrate rosemary selection grows 12 to 16 inches tall by 4 to 6 feet across. First developed at the Huntington Botanical Gardens in California, it has dark green aromatic foliage and deep blue flowers that attract bees.
Miss Jessopp’s Upright with light blue flowers and a strong aroma, ‘Miss Jessopp’s Upright’ rosemary is a delight in the garden. It can grow very tall and sturdy into a well-shaped shrub with dense foliage.
Rex a very robust variety that can grow up to about 4’ tall. It has dark blue flowers set on dark green foliage.
Roseus this upright rosemary produces lovely pink coloured flowers that contrast nicely with its green foliage. It can grow into a small shrub up to 1m tall. It has wonderfully aromatic foliage for using in the kitchen.
Salem the variety makes an excellent hedge and can grow up to 4’ tall. It has dark green foliage with pale but striking blue flowers. This variety needs protection from hard freezes as it is only moderately winter hardy.
Spice Island possibly the most aromatic rosemary, ‘Spice Island’ is sure to please. It has silver green foliage and grows up to 3’ tall.