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Mosquitoes Repelled By Fragrant Plants

Mosquitoes are a pain for every gardener, and over the years a number of plants have been recommended to repel mosquitoes.  Almost all of these plants are fragrant and include such things as catnip, citronella grass, beebalm, marigolds, lemon balm, lavender, geraniums, thyme, wormwood, rosemary and various mints. If you plant these in your garden you will have less mosquitoes – or so the proponents claim.

Will plants growing in your garden or on your deck keep mosquitoes away?

Mosquitoes Repelled By Fragrant Plants

Mosquitoes Repelled By Fragrant Plants

Why Fragrant Plants?

Why is it that all of the recommended plants are fragrant?

One can only guess at how these legends get started, but we do know that mosquitoes can smell us. They can sense the presence of various chemicals in the air and they can even smell the carbon dioxide you breath out from 50 meters (150 ft) away.

Deet, the most common mosquito repellent, is also fragrant. I think we have conditioned to think that to be effective a mosquito repellent needs to be fragrant.

Consider this – mosquitoes can smell or sense carbon dioxide that is completely non-fragrant to humans. Maybe we should be looking at non-fragrant plants to repel mosquitoes?

Do Fragrant Plants Repel Mosquitoes?

The citronella plant, also called citronella grass, does not repel mosquitoes. It gives off very low levels of fragrance which have little or no effect on mosquitoes.

The mosquito plant, Pelargonium citrosum, has been tested on human subjects, as reported in Mosquito Plant, Pelargonium Citrosum – The Citrosa Plant , and it has no effect on mosquitoes even though it is quite fragrant.

There are reports that there are fewer mosquitoes in eucalyptus groves – but most of us can’t grow these. Some reports have looked at plants that are used in Africa, reference 2, as natural mosquito repelling plants, but none of the plants reported include the fragrant ones on the above list and testing was done inside experimental huts.

I found no scientific studies that looked at the repellency of garden plants. Many web sites list plants that repel mosquitoes, but none provide a reference to their source of information. Dr. Tucker, a fragrance expert (ref 3) stated that “plants release significant amounts of their repellent oils only when their leaves are crushed . The important fact to remember is that no plant – citrosa, lemon thyme or even citronella grass itself will repel skeeters just sitting in a pot.”

Except for anecdotal stories, I have found no evidence that garden variety plants repel mosquitoes to any significant degree. The one plant that was specifically marketed for the job, mosquito plant, Pelargonium citrosum, was tested and found not to work.

Plant Extracts

Extracts from a number of fragrant plants have been tested and several do repel mosquitoes. But this is only after the active ingredients are concentrated and applied directly to the skin. The effectiveness of most extracts that work is short lived to 2 hours or less. In comparison, low concentrations of DEET are effective for 6-8 hours.

The fact that concentrated plant extracts, when applied to the skin, repel mosquitoes does not mean the plants will have the same effect.

For more details on natural plant repellents have a look at Mosquito Repellents – Best Options.

Do Plants Repel Mosquitoes?

It is very likely that some smells from plants affect mosquitoes. However, the concentration of such odors are very low and therefore have a limited effect. It seems highly unlikely that a plant 5 feet away, or sitting beside you on a patio will keep mosquitoes away.

If you feel this conclusion is incorrect, please post a reference that contradicts this conclusion. Don’t just tell me that the plants work for you. Find me a scientific study that shows plants repel mosquitoes.

References:

1) Fragrant Mosquito Repellents: http://www.huffingtonpost.com/2012/05/29/fragrant-mosquito-repellants-mint-chocolate_n_1553496.html

2) Repellency of Live Potted Plants Against Anopheles Gambiae From Human Baits in Semi-field Experimental Huts: http://www.ajtmh.org/content/67/2/191.short

3) Mosquito Repellent Plants: http://www.ipm.iastate.edu/ipm/hortnews/1993/5-26-1993/plant.html

3) Photo Source: Sanofi Pasteur

Robert Pavlis
Editor of GardenMyths.com
I live in southern Ontario, Canada, zone 5 and have been gardening a long time. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

I hope you find Garden Myths an educational site that helps you understand your garden better.

24 Responses to 'Mosquitoes Repelled By Fragrant Plants'

  1. Lena says:

    What about carnivore plants. Aren’t they also good mosquito killers? Or do the plants prefer other types of insects?
    ***
    Would an indoor goldfish in a bowl also eat mosquitos?

  2. lori says:

    To kill mosquito larvae I use a product called mosquito bits or dunks. You put it in any standing water and it kills the larvae for 2 weeks to a month depending on the product. It says it is safe for plants and animals. I can only take their word for that. It does kill the larvae.

    • Calvin pegues says:

      First, I and my baby are mosquitoe magnets and I was going to reclaim my yard this year, So found some info on the net lol and tried it. At first I was cynical but the ingredients were cheap and it sounded easy so I thought I would give it a try. The yard was a dry weedy mess and I was ready to start working on it again so I decided to spray first. I went to the dollar store and bought a bag of mouth wash original scent, Epsom salt and a bottle of beer that I had in the fridge. A third of all three, Set the dail to 3.5 and started spraying. My yard went from literally flying bugs everywhere almost nothing. After cleaning the yard I was so comfortable I bbqed shirtless with 0 bites. I’m waiting to see what happens after the first rain.

  3. Miriam says:

    Great article Robert, but do you believe that some plants attract more mosquitoes than others? I’m from Angola, where malaria is a big issue and am now moving to a house with a backyard. Would like to have plants there but perhaps could avoid mosquitoes’ favourite species?

    • Not sure. Around here they do seem more abundant near some evergreens, but that could just be due to the better hiding places these provide. Open areas like lawns have fewer mosquitoes than wooded areas, for the same reason.

    • Rosie says:

      Miriam avoid any plants that ‘catch’ and contain water – such as bromeliads – as they provide places for mosquitoes to breed.
      Great site Robert!

  4. Bonnie says:

    I check my yard frequently for any place a mosquito can lay eggs. Considering they can lay eggs in as little as a 1/2 tablespoon of water, this could be almost anywhere. I know some people forget to check saucers under plants, concrete downspouts which may have chipped area or two where water can puddle.

    I did read about a 2010 study at Iowa State University where they found that catnip was more effective at repelling mosquitoes than was DEET. I’ve also read that courmarin–an ingredient in repellents–was found in the leaves of ageratum–of course crushing the leaves was recommended. And while I have not read about a study of lemon balm, I have often found a handful of leaves crushed and rubbed on my arms did seem to keep off the mosquitoes–who usually love me.

    • I think you may be referring to a 2001 study – I could not find a 2010 study. It was work done in the lab, not in the field. It claimed, or at least reporters claimed the active ingredient in Catnip, nepetalactone, is 10 times more effective than DEET. DEET is something like 95% effect. So this stuff is 950% effective – mathematically impossible. Another reader made a comment that the experiment was flawed. The nepetalactone absorbed into the plastic tubes used, and as a result the experimental data was flawed – don’t know if that is true.

      One reported title was “Catnip Repels Mosquitoes More Effectively Than DEET” – but the study never test catnip! http://www.sciencedaily.com/releases/2001/08/010828075659.htm

      What is odd is the fact that since 2001, no one else has been working on Catnip extracts for mosquitoes. Maybe they did not work as well as reported in the original study?

      • Gust says:

        If you read the actual study numbers–it’s not 950% more effective in the way you lay it out. They are using 1% solutions. A 1% solution of the catnip oil was 10 times as effective as a 1% solution of DEET. It took a 10% solution of DEET to match the effectiveness of a 1% solution of the catnip oil. I’m sure a pure 100% solution of DEET is highly effective–it will also melt plastic and synthetic plastic-based fibers in clothes. The study needs to be reproduced but the numbers make complete sense. Nothing is 100% effective–the argument is that the catnip oil reaches that flatline of ~95+% (or whatever the ceiling is) significantly faster through lower concentrations than DEET.

        • You are correct that less catnip oil is as effective as the DEET tested, but that does not mean it is 10 times as effective. Most of the products soil for mosquito repellencies are effect at lower dose but they don’t last as long. The same can be said for DEET. DEET is also very effective at lower doses but it just does not last very long.

          The statement “ten times more effective” is nonsense when something is already 95% effective.

          Even if lower dosses of catnip keep mosquitoes away for as long as DEET, it does not mean that the lower doses are actually safer.

          • Kyle says:

            Just to clarify, in statistics, 10x higher effectiveness is applied to the ineffective portion. In other words 10x more effective than 95% means 1/10 x 5% = .5%, so the claimed effectiveness here would be 99.5%. Which seems pretty far-fetched to me, for any substance. But the discussion of common concentration levels(i.e. if a common low DEET concentration level is perhaps 70% effective and the same concentration of this is 97% effective) could be plausible.

          • I don’t agree with your clarification, but I could be wrong. I think 10x more effective than 95% means 1/10 x 95% = 104.5% effective.

          • Harold Balsogna says:

            Yes, you’re wrong. 10x as effective means 1/10th as many bites, e.g. 99.5% effective, or same effectiveness with 1/10th concentration, e.g. 1% vs 10%.

          • I asked which is correct on the Garden Professors FB Group. Some agreed with my way of thinking, and some with your way. Most agreed with you.

            Seems like one of those areas that is either poorly defined, or very confusing.

          • Steven Bradley says:

            You should probably ask in a Statistics / Mathematics Professors FB group

  5. Maria Macl says:

    Great article – very informative and just what I was looking for. I live in a suburb of London UK and have a tiny pond in a shady area of my garden containing only aquatic plants and a small solar powered fountain, which means the pond is static a lot of the time and this summer I’ve been constantly scooping out mosquito larva and pupae. I was looking for information about anything I might grow or place round the pond to repel them and, in spite of the discouraging information, I would still have tried a citronella if I had the right conditions for it to thrive but I don’t.

    That study at the University of Guelph was so risible I can’t imagine why they even bothered to publish it. A study of 8 participants? They’ve gotta be kidding!

    • Add some gold fish – they love eating mosquito larvae.

      The kind of study done by the University of Guelph was extremely important. Too many researchers look at the way mosquitoes respond in the lab. That can be useful information, but does not translate into an actual decrease in bites in the field. At some point you need to go into the woods and see what happens with real people and proper controls.

      You might be interested in reading the comment by Branko on June 11, 2015 at 4:40 am (Edit) in http://www.gardenmyths.com/citronella-plant-keeps-mosquitoes-away/#more-1319

      • Maria Macl says:

        Thanks. I don’t have fish because I have cats but I seem to have solved the problem by replacing the water and checking regularly – I don’t see any larvae or pupae now. Of course it’s important to have controlled trials with real people in the woods but a trial of 8 people is too small to produce a reliable result.

        • The study was repeated several times until they got statistically significant data – according to their report.

        • Mon says:

          Mosquito Dunks work well. They look like little donuts and don’t hurt anything g but mosquitos.

          • Mon says:

            The Mosquito Dunks are only for the water.

          • Brad says:

            Mosquito dunks also hurt fungus gnats–but that’s a feature, not a bug (so to speak). I use BTI (the strain of BT that’s used in dunks) against fungus gnats far more than against mosquitoes, and of course exclusively for fungus gnats for indoor plants.

            Sure, that still leaves aphids and spider mites, but that’s why nature gave us hippodamia convergens (yes, convergent ladybird beetles, which live free-range among my indoor plants at times) and science gave us beauvaria bassiana GHA (Botanigard).

  6. Beryl Jackson says:

    When we lived in Massachusets, where mosquitoes are rampant, I rubbed feverfew leaves directly on my skin. This kept the mosquitoes at bay for a time. Yes, a spray is easier.

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