Salvia rosmarinus (Rosemary)
Salvia rosmarinus, previously known as Rosmarinus officinalis and commonly called Rosemary, is a woody evergreen shrub with needle-like leaves which are green on top and whitish underneath. Depending on the cultivar, the flowers can vary in colour: white, pink, purple and blue.
It thrives in adverse climatic conditions with extreme temperatures and prolonged droughts. It is native to the Mediterranean basin but can be found worldwide.
HEIGHT & WIDTH
Rosemary scientific name
- Botanical name: Salvia rosmarinus (SAL-vee-uh rose-ma-REE-nus)
- Family: Lamiaceae (lay-mee-AY-see-ee)
- Synonym: Rosmarinus officinalis
- Common name: Rosemary
|Salvia||Latin word meaning “saving, healing” which refers to these plants’ medicinal properties.|
|rosmarinus||“Dew of the sea“. Derives from the Latin words: ros “dew” + marinus “of the sea”. Probably named this way because it grew near the coasts.|
Similar to what happened to the Russian sage, Rosemary was also recently reclassified as a Salvia. This reclassification is effective since 2019. The previous name Rosmarinus Officinalis is now considered its synonym.
How to identify Salvia rosmarinus
The shrub’s form can be upright, round, or spreading, depending on the variety. It has multiple brown woody branches.
It has an average height of 0.8 to 1m (2.6 to 3.2 ft). The width is around 60 to 80 cm (2 to 2.6 ft).
The stems are square-shaped with short internodes and opposite growing leaves with a bundle of 4-6 additional leaves at the axils. The flowers appear in clusters at the leave’s axils and usually are present at the upper ends of the stems.
The leaves are Sclerophyllous (“hard leaf”) which means they have certain characteristics that enable adaption to extreme temperatures and prolonged periods of drought.
- The leaves are small and narrow with enrolled margins, minimising exposure of the leaf´s surface to sun rays to avoid evaporation.
- The top of the leaf is green (mid to dark green depending on the variety) and shiny with a thick leathery layer (cuticle), that prevents water loss during dry periods.
- The bottom of the leaf is whitish and densely haired to preserve moisture and to insulate the leaves from solar radiation and severe cold.
The leaves are about 10 – 41mm | 0.4 – 1.6 in.
The flower is 2-lipped. The upper lip has two petals, while the lower lip has one large cup-shaped petal and two smaller lateral petals (wing petals). Inside the corolla, there are 2 arcing stamens and a single arching pistil longer than the stamens.
The flowers can be white, pink, purple or blue (depending on the variety) and measure about 8.5 -13.5mm | 0.3 – 0.5 in.
The calyx forms three sharp triangular fused sepals.
Quick tips to identify Rosemary
Salvia rosmarinus usage
Rosemary is a very versatile plant. Besides being a decorative plant in the garden, it is also used for other purposes due to its flavour, fragrance and chemical properties.
Rosemary is attractive and drought-tolerant, so it is commonly used for xeriscape gardening.
It may come in various forms, so it can be pruned into a ball shape, left growing upright or used as a groundcover in the case of some varieties with a spreading habit.
It is commonly used in aromatic gardens and aromatherapy due to the fragrance released by its essential oils.
Rosemary oil has a pleasant aroma, so it is used in perfumes, soaps, lotions and other cosmetic products.
Salvia Rosmarinus is a medicinal plant, and studies have demonstrated that it can be used to treat and prevent several disorders such as: “cardiac remodelling after myocardial infarction, body weight and dyslipidemia, cerebral ischemia, pain, infections, hepato-nephrotoxicity by lead,) stress and anxiety, and tumour cell proliferation. “
The details of this research can be found Journal of biomedical science.
How to plant Salvia rosmarinus
Like other Mediterranean plants, rosemary is dormant in the summer and its growth period is from Autumn to Spring. Therefore, rosemary should be planted in autumn to allow the development of its roots before the summer dormancy sets in.
Before planting rosemary, you should check your garden’s soil and sun exposure. You should prepare your soil for Mediterranean plants so that it is well-drained, and choose a place in the garden with plenty of sunshine.
How to water Salvia rosmarinus
Like most Mediterranean plants, Salvia rosmarinus is a Sclerophyllous (“hard leaf”) plant. This means that it has characteristics that enable it to survive in difficult environmental conditions such as extreme temperatures and prolonged droughts.
As this is a drought-tolerant plant, it typically does not require any water besides the winter rain once it is established. Generally, it will tolerate around four months of drought, but this may vary depending on the variety and other environmental conditions.
Once established, it should never be watered in summer because it is prone to infection from fungus in hot damp conditions.
During the first year after planting, you will need to water the young rosemary plant every two to three weeks during the summer. When it is very young, the roots are still not established and will need this extra water until they grow more deeply and can get water on their own at the deeper levels of the soil.
When watering it, you need to do it abundantly, giving the soil a generous soak so the water can penetrate deeply into the soil to allow the roots to grow deeply. Deep roots will allow the plant to survive longer periods of drought because the lower layers of the soil keep moist for more time.
Additionally, you should add mulch around your rosemary plant (but not too close to the base) to help it control weeds and conserve moisture. Wood chips or gravel are great options for mulching your rosemary plant.
How to prune Salvia rosmarinus
If you want your rosemary to stay healthy, beautiful and fragrant for many years, then you will need to learn how to prune it.
To know where to prune, you first need to understand how rosemary grows. Looking at a stem, you will notice that it is woodier and barer at the base and greener and leafy at the tip.
When you make a cut on a stem, two new branches will grow from that place. So if you cut all the stems, you will stimulate many new branches, creating a denser bush that produces more flowers.
You can prune your rosemary by cutting anywhere in the stem, but always above the woody part and leaving plenty of green leaves below. If you cut into the woody bare part of the stem, it will not regrow; all you get is a cut woody stem that will eventually die.
You can do two kinds of pruning depending on what you want to achieve: light pruning and hard pruning.
Light pruning encourages the production of more blossoms to extend the flowering season.
- This pruning consists of removing the stems’ tips right after the blossoms fade. The new growths will produce fresh new flowers.
- This type of pruning is usually done from late spring to mid-summer.
Hard pruning is done to help you maintain the size and shape that you want the shrub to have. It also promotes the growth of additional stems making your rosemary more dense and pretty.
- This pruning consists of cutting down to the base of the stem but still leaving plenty of green leaves below. Usually, 1/4 to 1/3 of the stem is removed.
- This type of pruning is done once a year, usually in early spring.
Ideally, you should start pruning your rosemary when it is still very young and without woody stems.
You should also remove any damaged branches all the way down to the ground.
Even with regular pruning, you will notice that your rosemary plant becomes very woody after some years. This is the time to replace it.
How to propagate Salvia rosmarinus
Rosemary can be propagated from seeds or cuttings, but the most common process is from cuttings.
Propagating from seeds
Growing Rosemary from seed is not easy. The germination rates are usually low, so you will need to plant many seeds to get a few good plants. Also, you will need to be very patient because you must wait several months before the plants are ready to plant. Plan to start seeding in mid-winter so they can be ready to transplant in mid-spring.
To grow Rosemary from seeds, you follow the same steps as for most shrubs. You can find detailed information about this process in the book: “Propagating Plants: How to Create New Plants for Free“
Propagating from cuttings
The most frequent method to propagate rosemary is to use cuttings. You can take the cuttings when you prune your rosemary, usually after they have flowered. The pruned stems can be used as your cuttings for propagation. This is a fairly easy process, and you can follow the steps in this article to propagate your rosemary from cuttings successfully.
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Sources of information used for this article
Article from North Carolina Extension Gardener