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Mosquito Repellant Plants
“Hi Dr. Kris
Do you know of any organic methods for reducing mosquitoes in my garden? I know that I can fumigate the whole garden but are there any other natural alternatives to reduce or deter mosquitoes from my garden, rather than resorting to poisoning the air with harmful chemicals? Any advice appreciated, thanks.
Pete, Sanur”

The best way to begin to reduce mosquitoes in and around your garden is to reduce their habitat and breeding sites. Mosquitoes typically prefer damp shady areas, so a simple garden cleanup will go a long way to reducing their numbers. Prune and weed out any areas of your garden which may be overgrown because mosquitoes love to take sanctuary in these areas. Prune out overgrown trees to let more sunlight and air circulation through the garden. Long overgrown grassy areas can particularly be a problem, so you should keep the lawn consistently trimmed. Tall grass and weeds are great daytime hiding places for adult mosquitoes.

You can also stop plagues of mosquitoes from breeding in your backyard. Mosquitoes lay their eggs in stagnant water, so you can reduce breeding opportunities by eliminating sources of standing water in your yard. Fix all outdoor taps that drip. Turn your empty pots and containers upside down to prevent them from collecting water. Drain your plant trays that collect water once every few days. Clean and refill pet drinking water daily. Remove any items from the garden that may hold water including buckets and children’s toys. Keep all drains free from obstructions such as weeds, leaf litter, rocks, etc. Mosquitoes can breed in just a few millimeters of water so you should aim to keep your garden clear of any breeding opportunities.

Aerate ponds and stock them with mosquito eating fish such as minnows and goldfish. For water gardens or ponds that do not contain fish add Bti (a strain of the naturally occurring bacteria Bacillus thuringiensis) to control mosquito larvae. You can find Bti in most large garden stores or online, sold as “Mosquito Dunks” or “Mosquito Bits.” In addition to these practical measures there are also a number of plants that you can grow that will help you reduce the attractiveness of your yard as a home for mosquitoes. As one more way to keep mosquitoes away from you and your garden, try these plants.

Citronella grass - Cybopogon nardus - Citronella is a perennial, clumping grass which grows to a height of 2 metres. It can be grown in the garden or near the patio. Ideally it should be positioned in the background, behind small decorative flowers and shrubs. It is closely related to lemongrass (Cymbopogon citrates), and looks very similar, with red base stems. This is the species used for the production of citronella oil, which is used as an insect repellent in sprays and candles, and even in aromatherapy. This should be easy to find in Indonesia, known as Serai wangi, it became very popular as a house plant during a dengue fever outbreak years ago. Commonly used in villas and hotels in Indonesia for the same reason. Citronella is the most common natural ingredient used in formulating mosquito repellents. Although citronella is used in many forms, such as scented candles or oil burners, the living plant is more effective because it has a stronger smell. The oil itself doesn’t kill mosquitoes but merely deters them, and a few areas of citronella around the garden do a good job of keeping away the pests. You can also plant several citronella plants in pots which can be moved around outdoor seating/patio/living areas, places in which mosquitoes commonly take refuge. Before having outdoor activities brush the citronella grass to release its scent.

Catnip - Nepeta cateria - One of the most powerful mosquito repellant plants is ordinary catnip. Research shows that nepetalactone, which is the essential oil found in catnip, is more effective than DEET at repelling mosquitoes. Entomologists at Iowa State University reported to the American Chemical Society that catnip is up to ten times more effective than DEET, the toxic chemical found in most commercial insect repellents. A relative of common mint, catnip is easy to grow and quick to spread. Famous for its intoxicating effects on cats, the leaves also make a refreshing tea. While catnip will repel mosquitoes in close proximity to the plant, some people apply crushed catnip leaves to the skin for more complete protection.

Ageratum - Ageratum houstonianu - Ageratum is a groundcover plant which reaches heights of up to 50cm, and is easily recognized by its blue flowers, although there are varieties in other colours. It is often displayed in rock gardens where low growing plants and groundcovers are favored. Ageratum emits a smell which mosquitoes particularly dislike. The plant secretes coumarin, which is used in some commercial mosquito repellents. Although the leaves of Ageratum can be crushed to increase the emitted odor, it is not advisable to rub the crushed leaves directly on the skin as it has some other less desirable elements that you don’t want on your skin in quantity, and it could make you sick.

Marigolds - Calendula officinalis - Marigolds have commonly used by gardeners to repel aphids, but it has recently been discovered that they are also powerful mosquito repellent plants. Mosquitoes seem to despise the smell of marigolds, so a few patches around the garden will help. Marigolds contain pyrethrum, a compound used in many insect repellents. Potted marigolds can be positioned near entrances to your home and any common mosquito entry points, such as open windows. The smell may deter mosquitoes from going past this barrier. Besides repelling mosquitoes, marigolds repel insects which prey on tomato plants, so you may want to plant a few marigolds in your tomato bed for added protection.

Rosemary - Rosmarinus officinalis - This culinary herb is also a great, natural mosquito repellant. It is easy to grow tolerates drought, and is very fragrant. It is an inexpensive and attractive way to boost the appearance of the landscape and repel mosquitoes at the same time. With rosemary you can simply crush a few leaves and rub on your skin and clothing to enhance the effect.

Other plants that are reputed to repel mosquitoes include Peppermint (Mentha piperita), Lemon balm (Melissa officinalis), Lavender (Lavandula angustifolia), Neem Tree (Azadirachta indica), Clove (Syzygium aromaticum) and Tea tree (Melaleuca alternifolia)

You should try to position mosquito repellant plants out of the wind, around outdoor seating areas as mosquitoes love to hide in the calm air directly beneath outdoor furniture where they can attack unsuspecting ankles and feet. Next time you are planting, consider using some of these attractive ornamental plants that will also help to drive the dreaded mosquitoes away!

Dr. Kris
Garden Doctor
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Copyright © 2012 Dr. Kris
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