Mosquito season peaks in summer and nothing ruins a nice time enjoying outdoor activities than a swarm of blood-thirsty mossies gunning for you. We’ve all been there. Just as annoying is trying to relax and take in a home movie or quietly read a book while several of the vicious little beasts are circling around the room making a meal of your exposed parts or your pet’s ears. Australia is known for infestations of this dangerous pest, especially in the warmer areas. Mosquitoes are a health hazard and can be a problem especially if you live near water or are surrounded by trees. You can even be bitten through clothing. They can spread diseases like Ross River fever and Dengue fever. In warmer areas they are vectors that spread even nastier threats like Zika virus and Malaria. In fact, mosquitoes are responsible for more deaths in the world than anything else, even more than the loss of life from bad water sources.
To combat this pest, people turn to chemical insect repellents to cover their skin but this may be a two-edged sword, thought to cause health issues as well. However, there is an alternative solution provided by nature. Using plants is a natural way to repel mosquitos and flies but whereas some plants are known to help repel mosquitos and other insect pests they are not a fool-proof solution on their own.
It is the aromatic oils in the plant leaves themselves that can be repellent and these can be extracted to make simple sprays or salves to rub onto the skin. Alternatively, it is the scent the plant exudes that helps mask the scent produced by humans that is attractive to mosquitos thus interfering with the insect’s ability to locate human hosts or their pets.
Ironically, the plants that repel mosquitos are often both attractive and pleasant smelling to humans, consequently they are popular as indoor plants or as potted plants on our decks, balconies and door steps.
I have put together a summary of some of the better-known plant varieties that are known to provide naturally occurring mosquito and insect repellent properties. Many of these plants are popular herbs which provide a range of other benefits, including medicinal and culinary properties. The plants that follow are ideal as house plants, suitable either as indoor potted plants or in pots and containers kept on our decks or porches and around our windows and doorways.
Citronella geranium (Pelargonium citrosum)
Crush the leaves for a pungent odour which is a natural insect repellent. Make a spray or rub it into your skin. The potted plant grows up to 1 metre by 70cm and produces attractive flowers. It is a hardy plant that does well with plenty of sun and light shade. It thrives better if kept well-drained. Keep them pruned when growing in planters.
Pennyroyal (Mentha pulegium)
Simply plant this known natural mosquito repellent around your house to discourage mosquitoes from the property and keep some inside for a delightful fresh aroma while it kills off any unfortunate pests that do enter the home. It is a perennial herb related to the mint family and if not planted in pots it can become invasive. The plant bears attractive reddish purple or lilac blooms and can become a delightful trailing plant when grown in a hanging basket or along the edges of pots and troughs. It likes a location offering plenty of sun to partial shade.
Citronella Grass (Citrosum)
The leaves are fragrant with the citronella scent which is pleasant to humans. Just crush the leaves and rub it onto the skin, the aroma can help to repel mosquitoes. This is a perennial clumping grass and can grow rather tall out in the garden. It is best kept in large pots, perhaps on the verandah or deck alongside entrances to your house. They do thrive in sunny to part shady locations and prefer good drainage and some fertiliser. It can stand to dry out a bit so when planted outside it still does well in drought-prone areas but doesn’t do well in cold areas if growing outside.
Lavender (Lavandula sp.)
Lavender is a comparatively strong insect repellent. The scent from lavender oil is thought to interfere with the mosquito’s ability to smell and thus reduces its ability to locate humans by our scent. Keep the potted plants in and around your house to deter mosquitoes entering and rub the crushed leaves on your skin to release its oils. This is an attractive, easy to grow perennial with a long flowering season. They need plenty of sunlight and good drainage so use a sandy potting mix. They respond well to regular liquid fertiliser which encourages prolific flowering and improves flower colour.
Lemon Balm (Melissa officinalis)
The bright green serrated leaves carry the scent of lemon and mint and it is known to be repellent to mosquitoes. It is a fast-growing perennial plant that also does well in a pot and can stand a little dryness. To release more of the active aroma crush the leaves in your hand and rub them on the skin.
Marigold (Tagetes sp.)
This daisy species contains pyrethrum which is a common ingredient in commercially sold insect repellents. They are easy to grow and produce abundant, pretty flowers. Remove the dead flower heads and this will encourage new growth. They get to about 30cmx30cm and prefer part sun. Use a good quality compost when planting and water them regularly. Keep them near your doors and windows to deter mosquitoes from entering the home.
Peppermint (Mentha hybrid)
While the aroma is pleasant to our senses, it acts as a natural insecticide, repelling mosquitoes. Apply it to your exposed skin for protection. The lovely pepper-minty smell is nice and fresh, and the plant is also widely used for culinary purposes so keep a few potted varieties around the house. It enjoys moist, shaded positions. If not kept in pots, it is a fast-grower that spreads runners everywhere.
Rosemary (Rosmarinus officinalis)
This perennial herb is an aggressive mosquito repellent. Its scent masks the smell emitted by humans and so disrupts the pest’s ability to zero in on you. You can make it into a simple salve for the skin or throw some into your camp-fire and the smell in the smoke will deter mosquitoes.
This is a hardy, easy to grow plant often used as a culinary plant as well as having medicinal properties. Kept indoors it needs exposure to plenty of sun and it prefers a well-drained soil. This herb can grow to 1.8m x 1m so prune it well to maintain your preferred size.
Catnip (Nepeta cataria)
This plant is related to the mint family. Its active repellent ingredient is the chemical nepetalactone. The essential oil if extracted has been shown to be very effective, but the plant also naturally emits the smell from the leaves. Crushed catnip leaves smeared on the skin provide a really good mosquito repellent. The plant is easy to grow and keep indoors but if you have a pet cat, they are very attracted to the scent and can nip the plant and roll around on it causing breakage.
Lemon grass (Cymbopogon)
The citronella oils in the leaves of this culinary and medicinal herb smell lovely and lemony and this scent is thought to block the ability of the mosquito to locate humans and pets. This is a fast-growing evergreen perennial and can grow quite tall. It prefers a well-drained alkaline soil and is frost tender. It needs plenty of sunlight so it should be located in sunny positions in the house or outside on decks or verandahs.
Basil (Ocimum basilicum)
This herb excretes a scent that strongly repels mosquitoes without having to crush the leaves. Research shows that there are four mosquito repelling substances in basil plants. It is also used as a culinary herb and grows well in pots. It can reach around 90cm x 60cm in size and prefers part to full sun so keep it in a sunny position in your house. It needs a good quality compost or potting mix and prefers to be watered regularly. Keep it in pots on the porch or on the window sills to keep the pests out of the house.
Aside from applying the benefits of the fantastic plants we have just discussed, always check around your property in summer to help prevent mosquito populations from proliferating. Most water storage containers are enclosed and don’t present a problem but be sure to keep any containers, old tyres or pots dry if they are open to the elements in order to prevent mosquitos from breeding in any standing rainwater.