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Mosquito plant — fact or myth?

We have all heard the term “urban myth” a term that describes stories and supposed occurrences that never really happened and are not true, although they are widely believed to have happened or be true. Maybe we should coin a new phrase, “garden myth,” to encompass some of the things that gardeners believe even though scientific evidence seems to prove them wrong.

One of the myths that I have encountered is the belief that the plant commonly called “citronella” repels mosquitoes and that planting a couple of these plants on your patio will enable you to sit out during mosquito season without being bothered by them. There is no scientific basis for this belief. In fact, the common citronella plant, Pelargonium citrosum, is not even the source plant for citronella oil that is used in mosquito-repellent products. It does have a few of the same essential oils, but not enough, it seems, to make it the insect repellent that it is claimed to be. Scientific studies continue to find that mosquitoes are not repelled by the plant and in many studies mosquitoes seem to land without trepidation on the very plants they are supposed to be avoiding.

Even though citronella is not the mosquito repellent it is cracked up to be, it is still a useful plant in the outdoor garden and can be a solid performer as an indoor foliage plant as well. It is a large, bushy plant that can be used as a specimen foliage plant or it can be included in a large outdoor container or be included in a plant grouping in the interior landscape. The deep veining of the leaves gives them a rough texture while the leaves themselves are sturdy and attractive. Citronella has a strong medicinal aroma when the leaves are rubbed or crushed, but when the plant is undisturbed the scent is faint and quite pleasant.

It likes at least six hours of direct sun a day, so in the interior landscape it will be happiest in front of a sunny window or located in a sunroom. In the outdoor garden, a full-sun location will suit it although it will tolerate some shade. It is generally pest free, although one year for some reason, I did have an infestation of white fly on my citronella during the winter. Since then I am vigilant and check the undersides of the leaves occasionally, and brush against the foliage from time to time that will allow me to spy any lurking pests.

A loose, well-draining planting medium should be used in a container that has good drainage. Using a fairly large and heavy container will ensure that the plant does not get top heavy and fall over as citronella can get nearly two metres in height if not pruned. Cutting back the top stems will cause the plant to bush out and not grow as tall.

Citronella does bloom, producing small lavender blooms that are quite dainty and pretty, which is a contrast to the rest of the plant that tends to be rather coarse and large. The plant, however, is grown mainly for its foliage.

Even if they do not keep the mosquitoes in your outdoor garden at bay, you might still find a use for a couple of citronella plants in your garden. You may even want to keep believing in its mythical powers!

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