Rosemary Bonsai Care


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General Background:

The Latin name for Rosemary is Rosmarinus officinalis, which translates to “mist of the sea,” as its gray-green foliage is thought to resemble mist against the sea cliffs of the Mediterranean, where this lovely plant originates and can be found growing in heights up to 5 feet.  However you don't need perfect sunshine, sea mist or a never ending summer to successfully grow Rosemary Bonsai. In fact, more Rosemary plants suffer from too much attention than from too little.  The three fundamentals for successfully growing Rosemary are: Sun, Good Drainage and Good Air Circulation, which any conscientious beginning Bonsai enthusiast can easily provide.

Trees Features:

Rosemary is an attractive evergreen shrub with needle-like leaves and brilliant blue flowers. The delicate flowers of Rosemary persist through spring and summer, filling the air with a soothing pine fragrance. In its natural habitat it blooms almost all year, commonly being used in ornamental plantings for landscaping.  Rosemary has interesting, fibrous bark, which the plant sheds partially making this bonsai plant look very old and interesting even when it is still young. This Bonsai will be healthiest outside, and can be difficult to grow inside but with proper attention, lighting, and location you will find that this beautiful herb is easy to care for and is not only attractive, but is useful for seasoning the traditional dishes in Mediterranean cuisine.


Rosemary plants require very little care and can be grown outdoors as long as the temperatures in the winter do not drop lower than around 10 degrees F.  If you live in a frost free area, you can easily grow your Rosemary Bonsai outdoors year round.  Be sure to provide a sandy, well draining soil and 6-8 hours of full sunlight.  These plants thrive in warm, humid environments and cannot take extremely cold or extended periods of dry indoor environments.  Since rosemary cannot withstand winters below 30 degrees, Rosemary is perfectly suited for Bonsai as it does best when grown in containers so that it can easily be moved indoors when the weather is not to its liking and protect it from drafts.  Move your Bonsai back outdoors once all danger of frost has past as it does not particularly enjoy the conditions offered inside and will die without proper care.


When indoors, it does best near a patio door or southern facing window where it can get 6-8 hours of light and warmth from the sun.  If this much sun exposure is not possible, artificial lights may be needed for your Bonsai to thrive as sunlight is critical.


You will have to water your Rosemary Bonsai quite often because they are very sensitive to drought conditions.  Rosemary prefers to remain somewhat on the dry side; therefore, terra cotta pots are a good choice when selecting suitable containers. These pots allow the soil to dry out faster. Thoroughly water rosemary plants when the soil is dry to the touch but allow the plants to dry out between watering intervals. Ensure that it doesn't bake and completely dry out while outdoors during the summer. When watering rosemary, the soil in the pot it is planted in must have good drainage because rosemary is also sensitive to overwatering. Be sure there is plenty of drainage and adequate moisture offered to ensure health. The better you water a Rosemary plant, the larger they will grow. 


Rosemary is not a heavy feeder, but it will do well if fertilized in spring with a fish/kelp emulsion to ensure a healthy start for the growing season. Periodic foliar sprays with the emulsion will keep it looking great.

Pruning / Training:

Because Rosemary is first and foremost an herb, it responds well to the conditions that herbs experience; namely, most herbs thrive on being trimmed every now and then, especially those used for flavorings.  Snip sprigs just as you would when cutting back a houseplant, trimming rosemary once blooming has ceased.  The general rule for trimming is not to take more than one-third of the plant at any time and make cuts just above a leaf joint.  These can then be dried like any other herb by hanging tied bundles upside down in a cool, dry environment.  Since the branches are somewhat stiff, wiring is needed to shape them.  Keep in mind that the diameter of the branches to be shaped must be only half that of a pencil or you will risk breaking them when you attempt wiring them.  The branches can be formed into beautiful cushion shapes by repeatedly reducing the shoots and you will find that your Rosemary Bonsai lends itself beautifully to cascade forms that capture the natural windswept look it obtains in its native environment.

Insects / Pests:

The biggest problem with growing Rosemary indoors is its tendency to develop powdery mildew which is a white, powdery fungus that can develop if the surrounding air is humid and there is not enough air movement.  Powdery mildew won't kill your Bonsai, but it will weaken the plant making it more susceptible to insect attack or further disease.  Keep the humidity low by allowing the soil to dry somewhat between watering, keeping the plant in sunlight and, if necessary, running a fan for a few hours a day to create a breeze.  Also be on the lookout for aphids and spider mites.  Catching them before a total infestation will make them easier to control.  An effective remedy to take control of many insect pests is to make a diluted soap and water solution.  Spray the leaves until the solution runs off, gently wipe leaves with a soft sponge, rinsing after each pass to ensure aphid removal.  Take a final rinse with pure water and keep your eyes peeled in the days following for further attacks! 


Rosemary plants are usually propagated by cuttings, as they can be tricky getting evergreen rosemary seeds to germinate.  Start new plants with cuttings from existing evergreen plants.  Cut stems that are about two inches long and cut remove any leaves.  Place the cuttings in a mixture of perlite and peat moss, spraying with water until roots begin to grow.  Once roots have developed, you can plant the cuttings as you would with any Rosemary plant.


As with most potted plants, the soil in your rosemary pot will degenerate through watering and root growth. Repot at least once a year. Spring is a good time to repot your rosemary, but it should be fine no matter what time of year you get to it. When the Rosemary Bonsai puts out considerable growth or looks like it just can't get enough water, it has outgrown its pot and needs to be transplanted into a larger one. If you want to maintain the size of your Bonsai, slice off a couple of inches of the roots from the bottom and sides of the root ball and replanting in the same pot. Be sure to trim some of the top at the same time, to lessen the work load of the roots and the stress placed upon the trimmed plant. Allow your repotted Bonsai some time to recover and it reward you with many more seasons of snippings.

Additional Comments:

Rosemary is a wonderful addition for soups and stews, and adds fragrance and spice to things like breads and flavored butters. You can make a country herb mixture with rosemary, thyme and oregano for your sauces. The volatile oil in Rosemary leaves is also used as an antimicrobial substance that can be used as an effective and soothing medicinal remedy for colds and Bronchitis. There are so many different things you can do with a rosemary plant that taking the steps to ensure your Rosemary’s health probably seems like a small duty to have in order to reap the benefits this amazing plant has to offer. 

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